Final Report on the Risk Assessment of the Mercury Spill in...

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Final Report on the Risk Assessment of the Mercury Spill in

Northern Peru

Prepared for: Minera Yanacocha S.R.L.

Av. Camino Real 348 Torre El Pilar, Piso 10

Lima 27, Peru

Prepared by: Shepherd Miller

3801 Automation Way, Suite 100 Fort Collins, Colorado 80525

November 2002

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FINAL REPORT ON THE RISK ASSESSMENT OF THE MERCURY SPILL IN NORTHERN PERU

TABLE OF CONTENTS

EXECUTIVE SUMMARY……………………………………………………………….. ES-1 1 INTRODUCTION .........................................................................................................................1

1.1 Project Background..........................................................................................................1 1.2 Mercury ..........................................................................................................................2

1.2.1 Introduction.......................................................................................................2 1.2.2 Environmental Cycling .......................................................................................4 1.2.3 Typical Background...........................................................................................8

2.0 RISK ASSESSMENT PROBLEM FORMULATION............................................................ 12 2.1 Identification of Contaminants of Potential Concern (COPCs)........................................... 12 2.2 Site Description and Ecological Resources ....................................................................... 13 2.3 Conceptual Site Model: Fate, Transport, and Potential Exposure ........................................ 16 2.4 Assessment and Measurement Endpoints......................................................................... 20

3.0 EFFECTS CHARACTERIZATION AND BENCHMARK SELECTION.............................. 22 3.1 Mercury Toxicity to Humans and Benchmark Determination............................................. 22 3.2 Mercury Toxicity to Other Terrestrial Animals and Benchmark Determination ................... 26

3.2.1 Birds and Mammals ......................................................................................... 26 3.2.2 Plants ............................................................................................................. 33

3.3 Mercury Toxicity to Aquatic Biota and Benchmark Determination..................................... 37 3.4 Benchmark Summary..................................................................................................... 41

4.0 EXPOSURE ASSESSMENT................................................................................................ 43 4.1 Sampling Associated with Remediation and Monitoring ..................................................... 44 4.2 Phase I (Year 2000) Sampling Conducted In Support of the Risk Assessment.................... 49

4.2.1 Terrestrial Sampling and Tissue Analysis........................................................... 49 4.2.2 Sampling and Tissue Analysis of Aquatic Biota.................................................. 61

4.3 November 2000 Sampling (Shepherd Miller, SENASA, MYSRL)...................................... 74 4.4 Phase II Sampling Conducted In Support of the Risk Assessment...................................... 76

4.4.1 Terrestrial Sampling and Tissue Analysis........................................................... 77 4.4.2 Sampling and Tissue Analysis of Aquatic Biota.................................................. 88

4.5 Mercury Transfer to Terrestrial Biota .............................................................................. 99

5.0 RISK CHARACTERIZATION .......................................................................................... 102 5.1 Aquatic Resources ....................................................................................................... 102 5.2 Human Health.............................................................................................................. 105

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5.3 Terrestrial Resources ................................................................................................... 107 5.3.1 Plants ........................................................................................................... 107 5.3.2 Animals ........................................................................................................ 108

6.0 SUMMARY AND CONCLUSIONS.................................................................................. 111 6.1 Summary..................................................................................................................... 111 6.2 Human Health.............................................................................................................. 111 6.3 Agricultural and Native Plants....................................................................................... 113 6.4 Terrestrial Animals ....................................................................................................... 114 6.5 Aquatic Resources ....................................................................................................... 115 6.6 Uncertainty.................................................................................................................. 116

7.0 REFERENCES .................................................................................................................. 119

LIST OF TABLES

Table ES-1 Summary of the RA Conclusions for each Assessment Endpoint.............................ES-4 Table ES-2 Mercury Concentrations in Aquatic Biota from Exposed and Reference Locations...ES-5 Table ES-3 Mercury Concentrations in Soil and Vegetation and Terrestrial Insect Tissue ...........ES-5

Table 1.2.1 Example Solubility of Some Forms of Mercury............................................................ 5 Table 1.2.2 Typical Units and Conversions ................................................................................... 8 Table 1.2.3 Ranges of Mercury Concentrations in Diets in the U.S.A., Canada, Scotland, Italy, and

Spain...................................................................................................................... 10 Table 2.1.1 Evaluation of Trace Constituents in MYSRL Mercury............................................... 13 Table 2.2.1 Mammal Orders and Likely Occurrence Near the Spill Area ..................................... 15 Table 2.2.2 Fish Species in the Jequetepeque River and Gallito Ciego Reservoir ........................... 16 Table 2.4.1 Summary of Assessment Endpoints and Measures of Effect and Exposure................. 21 Table 3.1.1 Representative Human Health Drinking Water Criteria ............................................. 24 Table 3.1.2 Listing of Values Reported as Safe Hg Limits by Various Countries and Regulatory

Agencies for Fish.................................................................................................... 25 Table 3.2.1 NOAEL and Effect Levels of Dietary Mercury for Mammals and Birds .................... 28 Table 3.2.2 NOAEL and Effect Levels of Mercury in Drinking Water for Mammals and Birds ..... 30 Table 3.2.3 Reported NOAEL and Effects Levels of Mercury in Animal Tissue .......................... 31 Table 3.2.4 NOAEL and Effect Levels of Mercury in Plant Tissue ............................................. 34 Table 3.2.5 NOAEL and Effect Levels of Mercury in Soil to Plants ............................................ 36 Table 3.3.1 NOAEL and Effect Levels of Mercury in Water to Aquatic Biota ............................. 38 Table 3.3.2 NOAEL and Effect Levels of Mercury in Aquatic Biota Tissue................................. 41 Table 3.4.1 Summary of Benchmark Mercury Concentrations ..................................................... 42 Table 4.1.1 Water and Sediment Sampling Locations .................................................................. 45 Table 4.2.1 Results of the Phase I Soil Samples.......................................................................... 51 Table 4.2.2 Results of the Phase I Vegetation Analyses.............................................................. 53

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Table 4.2.3 Summary Statistics for the Phase I Vegetation Sampling ........................................... 58 Table 4.2.4 Results of the Phase I Insect Tissue Sampling .......................................................... 59 Table 4.2.5 Summary Statistics for the Phase I Insect Sampling .................................................. 60 Table 4.2.6 Comparison of Soil and Insect Tissue Concentrations (Phase I) ................................. 60 Table 4.2.7 Mercury Concentration in Phase I Aquatic Macroinvertebrate Samples...................... 63 Table 4.2.8 Summary Statistics for the Phase I Macroinvertebrate Sampling ................................ 64 Table 4.2.9 Results of the Phase I Fish Analyses........................................................................ 67 Table 4.2.10 Summary Statistics for the Phase I Fish Sampling ..................................................... 72 Table 4.2.11 Mercury Concentration in Fish at Each Location (Phase I) ........................................ 72 Table 4.2.12 Mercury Concentrations for Each Fish Tissue Type (Phase I) ................................... 72 Table 4.2.13 Mean Total Hg Concentrations for Each Fish Species and Tissue Type (Phase I) ....... 74 Table 4.3.1. Results from the November 15, 2000 Plant and Soil Sampling .................................... 75 Table 4.3.2 Summary Statistics for the November 15, 2000 Soil and Vegetation Samples .............. 75 Table 4.3.3 Results from the November 15, 2000 Animal Tissue Sampling ................................... 76 Table 4.4.1 Results of the Phase II Soil Samples ........................................................................ 78 Table 4.4.2 Results of Vegetation Analyses from the Phase II Sampling ...................................... 80 Table 4.4.3 Summary Statistics for the Phase II Vegetation Sampling .......................................... 85 Table 4.4.4 Results of the Phase II Terrestrial Insect Samples Collected in 2002 .......................... 86 Table 4.4.5 Summary Statistics for the Phase II Insect Sampling ................................................. 88 Table 4.4.6 Mercury Concentration in Phase II Aquatic Macroinvertebrate Samples .................... 89 Table 4.4.7 Comparison of Mercury Tissue Concentrations (Phase II) in Macroinvertebrates at

Different Sample Locations ..................................................................................... 89 Table 4.4.8 Results of Fish Analyses from the Phase II Sampling ................................................ 92 Table 4.4.9 Re-analyzed Fish Tissue Samples from the Phase II Sampling ................................... 96 Table 4.4.10 Summary Statistics for the Phase II Fish Sampling .................................................... 96 Table 4.4.11 Mercury Concentration in Fish at Each Location (Phase II)....................................... 96 Table 4.4.12 Mercury Concentrations for Each Fish Tissue Type (Phase II) .................................. 98 Table 4.4.13 Mean Mercury Concentrations for Each Fish Species and Tissue Type (Phase II) ...... 99 Table 4.5.1 Mercury BAFs for Birds and Mammals ..................................................................101 Table 5.1.1 Calculated Hazard Quotients (HQs) for Aquatic Resources......................................103 Table 5.2.1 Calculated Hazard Quotients (HQs) for Humans .....................................................106 Table 5.3.1 Calculated Hazard Quotients (HQs) for Plants.........................................................107 Table 5.3.2 Calculated Hazard Quotients (HQs) for Terrestrial Animal Diets ..............................109 Table 5.3.3 Calculated Hazard Quotients (HQs) for Terrestrial Animal Tissues...........................110 Table 6.1.1 Conclusions From Assessment Endpoints, Measures of Effect, and Exposure ............112

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LIST OF FIGURES Figure 1.2.1 Global cycling and fluxes of mercury.......................................................................... 4 Figure 1.2.2 Local cycling of the spilt mercury............................................................................... 6 Figure 2.3.1 Conceptual site model of mercury transport and potential receptors in the terrestrial

ecosystems............................................................................................................. 18 Figure 2.3.2 Conceptual site model of mercury transport and potential receptors in the aquatic

ecosystems............................................................................................................. 19 Figure 4.1.1 Dissolved mercury concentration in water samples at each sampling location.............. 47 Figure 4.1.2 Average mercury concentration of sediment samples ................................................ 48 Figure 4.2.1 Scatterplot of Phase I soil Hg concentrations (dw) versus location ............................. 52 Figure 4.2.2 Total Hg tissue concentrations in the Phase I vegetation tissues collected at reference and

exposed locations.................................................................................................... 57 Figure 4.2.3 Scatterplot of mercury concentrations in insects versus location (Phase I). . ............... 61 Figure 4.2.4 Mercury concentration in macroinvertebrates versus sampling location (Phase I).. ...... 65 Figure 4.2.5 Mercury concentration in fish at all sampling locations (Phase I).. .............................. 71 Figure 4.2.6 Mercury concentrations (ww) in each fish tissue type plotted versus fish length (Phase I).

.............................................................................................................................. 73 Figure 4.4.1 Scatterplot of Phase II soil Hg concentrations (dw) versus location ............................ 79 Figure 4.4.2 Total Hg tissue concentrations (ww) in Phase II vegetation collected at reference and

exposed locations.................................................................................................... 84 Figure 4.4.3 Scatterplot of mercury concentrations in insects versus location (Phase II). ................ 87 Figure 4.4.4 Mercury concentration in macroinvertebrates versus sampling location (Phase II)....... 90 Figure 4.4.5 Mercury concentration (ww) in fish at all sampling locations (Phase II)...................... 97 Figure 4.4.6 Mercury concentrations (ww) in each fish tissue type plotted versus fish length (Phase

II).......................................................................................................................... 98

LIST OF MAPS Map 1. Mercury Spill Locations Map 2. Water and Sediment Sampling Locations Map 3. Ecological Sampling Locations Map 4. Sampling Locations for the November 2000 Sampling

LIST OF APPENDICES

Appendix A Oak Ridge National Laboratory RfD Derivation Appendix B SENASA and CONSULCONT Data Appendix C Water Data (Remediation Sampling) Appendix D Sediment Data (Remediation Sampling) Appendix E Homero Bazan Sampling Report- Phase I Appendix F ENKON Sampling Report Appendix G Frontier letter discussing methyl versus total in fish tissue Appendix H Homero Bazan Sampling Report- Phase II

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EXECUTIVE SUMMARY This report comprises the Final Risk Assessment (FRA) for the mercury spill that occurred in the

Jequetepeque watershed of Northern Peru on June 2, 2000. The methodology utilized in assessing potential

risk from this spill is consistent with the approach that was presented to the Ministry of Energy and Mines

(MEM) by Shepherd Miller on January 24, 2001, and as established with the independent reviewer, Dr.

Peter M. Chapman of EVS Environment Consultants, North Vancouver, Canada. The original timetable

for Risk Assessment (RA) activities included the presentation of a Preliminary Risk Assessment (PRA)

after analysis of sampling conducted in 2000. This preliminary report was to be updated and revised based

on the results of additional sampling conducted in 2001 after the first wet season. The revised report was

then to be issued as the final risk sssessment report. However, due to delays in obtaining permission to

send the samples collected in 2000 to the United States for analysis, the issuance of the PRA was deemed

impractical. Instead of presenting a PRA, the decision was made to issue a Draft version of the FRA that

includes analysis and discussion of all of the sampling conducted at the site. The Draft Final Risk

Assessment (DFRA) was provided to the MEM on September 30, 2002. No comments were received on

the DFRA. This report is therefore issued as the Final Risk Assessment Report.

The primary conclusion of the RA is that there are no unacceptable risks, as based on the comparison of

measured mercury concentrations to protective concentrations, associated with the mercury spill, to human

health or to terrestrial or aquatic ecological resources. There may have been some short-term risk to

terrestrial insects, as based on sampling conducted in 2000, but subsequent sampling indicated that any risk

to insects was no longer present by 2002. The finding of minimal risk (i.e., mercury concentrations below

protective values) to humans and the ecology of the Jequetepeque watershed is not unexpected given the

extensive and comprehensive response and spill cleanup activities conducted by MYSRL (MYSRL 2001).

The best estimate of the amount of the 151 kg of mercury spilt that is not accounted for, is six to nine

kilograms. This amount of mercury has a volume of 0.67 L. This volume is either widely dispersed over

the 40 Km spill area, or partially in the possession of individuals.

Risk assessment (RA) is a procedure for making environmental decisions based on the evaluation of

possible effects of an activity, in this case the spill of mercury, to the environment and to human health.

The risk assessment process can determine if a chemical release, such as a spill, has contaminated or

polluted an area. Contamination is defined as the presence of a chemical in excess of natural conditions

but below biologically available concentrations that result in risk, whereas pollution is defined as

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contamination causing adverse biological or health effects. The United States Environmental Protection

Agency (USEPA 1998) outlines three primary steps in conducting a risk assessment: 1) Problem

Formulation, 2) Risk Analysis, and 3) Risk Characterization. Essentially, the RA conducted for the

mercury spill used data collected at the site that measured the concentrations of mercury in different

environmental media (e.g., water and soil) and biological tissues (e.g., vegetation and fish) along with a

review and synthesis of the scientific literature on the effects, fate and transfer of mercury in the

environment, to assess the potential risk to humans, aquatic biota, and terrestrial plants and animals.

In the Problem Formulation step of the RA, mercury was confirmed as the only chemical constituent that

needed to be evaluated as a result of the spill. A conceptual site model (CSM) was developed that

outlined the fate and transport of mercury in the environment and identified the exposure pathways and

receptors that needed to be included in the RA. Receptors are species or biotic groups (e.g., plants) that

need to be considered in the evaluation of risk. From the CSM, four assessment endpoints were

established in order to evaluate the overall management goal of protecting the terrestrial and aquatic

resources of the Jequetepeque watershed that may have been exposed to the spilt mercury. The

assessment endpoints, which are listed in Table ES-1, are explicit expressions of the environmental values

that require protection.

A primary initial focus of the Risk Analysis step of the RA was to collect, analyze, and review data on

mercury concentrations in the environment following the spill. This process is called the Exposure

Assessment. Five sets of field data were collected between June 2000 and April 2002. The first set of

data is composed of water and sediment concentrations collected from June 2000 to April 2002. These

samples were collected by MYSRL in support of the spill remediation effort. The second set of data was

collected by Ministry of Agriculture- Servicio Nacional de Sanidad Agraria (SENASA) personnel and their

consultant, Consulcont SAC. These samples included vegetation, animals, fish, soil, and water.

Unfortunately, due to uncertainties associated with the sampling and analytical methodologies used, the

results of this sampling were deemed unreliable for use in the RA. However, the third set of data, which

was collected at three locations in or near Choropampa where SENASA had previously reported elevated

mercury concentrations in vegetation, was utilized. This dataset was collected in November 2000 by

MYSRL, SENASA, and Shepherd Miller personnel. The final sets of data were collected specifically to

support the RA. For this final effort, co-located soil, vegetation, and terrestrial insect samples were

collected from several locations that could have potentially been impacted by the spill (Exposed Locations),

and from several locations that were outside of the spill influence (Reference Locations). Samples of fish

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and macroinvertebrate tissues were also collected from several Exposed Locations and Reference

Locations within the Jequetepeque watershed. The first set of samples (Phase I) was collected in 2000

before the start of the first wet season after the spill. Phase II samples were collected in 2001 and 2002,

after the end of the first wet season following the spill. Because these data sets were the most extensive

and best-controlled sampling of mercury concentrations for the site, they are the primary source of data

used in the RA. In order to provide a high level of conservatism, and thus a high level of environmental

protection, the 95% Upper Confidence Level of the mean concentrations was used as the Exposure

Concentrations (ECs) in the RA.

The second aspect of the Risk Analysis step is called Effects Characterization. For this portion of the RA,

safe and toxic mercury concentrations reported in the scientific literature and from governmental and other

organizations (e.g., the World Health Organization) were reviewed and synthesized. The end result of the

Effects Characterization was the establishment of mercury concentrations that are protective of 1)

environmental media, such as water and soil, 2) the tissues of plants and animals, and 3) the diet of animals

that consume plants or other animals. These established protective concentrations are termed Benchmark

concentrations.

The final step of the RA is called Risk Characterization. In this stage, the EC values outlined in the

Exposure Assessment were compared to the Benchmark concentrations to evaluate risk potential. Risk

was evaluated through the use of Hazard Quotients (HQs). HQs are calculated by dividing the Exposure

Concentration (EC) by Benchmark Values (USEPA 1998). An HQ less than 1 indicates minimal risk.

HQs greater than 1 indicate that there may be the possibility of risk. The results of the Risk

Characterization are summarized in Table ES-1.

With only a single exception, the calculated HQ values for each of the assessment endpoints is less than

one, indicating minimal risk from the spilt mercury. The single exception is for mercury concentrations

measured in terrestrial insect tissues (HQ=1.68) during the September 2000 sampling. The follow-up

sampling conducted in 2002, however, found that the mercury concentrations in insect tissues had returned

to protective levels and that there was no longer any potential risk to this group.

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Table ES-1 Summary of the RA Conclusions for each Assessment Endpoint

Assessment Endpoint Measures of Effect and Exposure Conclusions

Measures of effect: regulatory benchmarks for concentrations of mercury in water and food

Direct measures of exposure: concentrations of mercury in fish, macroinvertebrates (crabs), vegetation, and water

Risk from ingestion of fish, crabs, plants and drinking water is minimal; HQs<1.

Health of individual humans who may consume water and food that may be influenced by the mercury spill

Indirect measures of exposure: modeled concentrations of mercury in terrestrial animal tissue using literature transfer factors

Risk from ingestion of terrestrial mammals and birds is minimal; HQs<1.

Measures of effect: established benchmark concentrations of mercury in soil and plant tissues from a review of the scientific literature

Survival, growth, and reproduction of populations of agricultural and native terrestrial plants within the spill area

Direct measures of exposure: concentrations of mercury in soil and vegetation tissue collected at the spill locations

Risk to plants from mercury in soil or in tissues is minimal; HQs<1.

Measures of effect: established benchmark concentrations of mercury in water and food from a review of the scientific literature and regulatory benchmarks Direct measures of exposure: concentrations of mercury in water and food items (vegetation and insects) collected at the spill locations

Risk to mammals and birds from water and dietary consumption is minimal; HQs<1.

Survival, growth, and reproduction of populations of terrestrial animals that may be exposed to mercury from drinking water, consumption of plants, or consumption of other animals Indirect measures of exposure: modeled

concentrations of mercury in terrestrial animal tissue using literature transfer factors

Risk to mammals and birds from mercury tissue concentrations is minimal; HQs<1. Potential risk to insects in 2000 (HQ=1.68), risk in 2002 is minimal; HQ<1.

Measures of effect: established benchmark concentrations of mercury in water and animal tissue from a review of regulatory guidelines and the scientific literature

Survival, growth, and reproduction of populations of aquatic biota (macro-invertebrates and fish) that may be exposed to mercury from the spill

Direct measures of exposure: concentrations of mercury in water and aquatic animal tissue

Risk to aquatic biota from water and tissue concentrations of mercury is minimal; HQs<1.

HQ= Hazard Quotient (discussed in Section 5, indicates minimal risk if HQ<1)

Other conclusions from the RA are that there has not been any detectable movement of mercury from the

spill sites into waterways. This conclusion is supported by water sampling conducted between June 2000

and April 2002 and by sampling of aquatic biota in 2000 and 2001. The 2000 sampling was conducted

before the onset of the first wet season after the spill and the 2001 sampling was conducted after the end

of the first wet season. The mean concentration of mercury in water at both Reference and Exposed

Locations was 0.017 ppb. Mercury concentrations in aquatic biota tissue at Exposed locations and at

Reference locations were similar for both sampling dates (Table ES-2). Overall, mercury concentrations

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in water and aquatic biota tissue at both Exposed and Reference locations are indicative of typical

background concentrations of mercury in the environment.

Table ES-2 Mercury Concentrations in Aquatic Biota from Exposed and Reference

Locations

FISH MACROINVERTEBRATES YEAR LOCATION ppb (ww)* ppb (ww)*

Upstream (Reference) 61.3 151.3 Downstream (Reference) 177.5 78.9 All non-spill (Reference) 167.0 67.8

2000

Spill locations (Exposed) 90.6 25.1

Upstream (Reference) 40.9 453.1 Downstream (Exposed) 234.4 98.9 All non-spill (Upstream+Downstream) 228.1 96.8

2001

Spill locations (Exposed) 94.1 26.7

* Values listed are 95% UCL of the mean from samples collected at the different location types.

While the sampling conducted in 2000 found that mercury concentrations in vegetation and insects

collected at the Exposed locations tended to be higher than those at Reference locations (Table ES-3), the

95% UCL of the mean concentrations were below protective levels for 1) plants and 2) animals that

consume vegetation or insects (Table ES-1). The soil samples that were co-located with the plants and

insects at the Exposed locations were not elevated relative to those at Reference locations. Furthermore,

concentrations in plant and insect tissue at both the Exposed and Reference locations significantly

decreased in the 2002 sampling, relative to the 2000 sampling. The 2000 sampling was conducted during

the dry season, whereas the 2002 sampling was conducted during the wet season. Based on these results,

it is believed that dry deposition of mercury on plant surfaces explains the seasonal differences in mercury

levels. The elevated concentrations of mercury in tissues collected in 2000 were likely a result of the air

deposition of mercury that was mobilized by spill remediation activities.

Table ES-3 Mercury Concentrations in Soil and Vegetation and Terrestrial Insect Tissue

SOIL VEGETATION INSECTS YEAR LOCATION ppb (dw)* ppb (ww)* ppb (ww)*

Reference Locations 432.9** 29.4 63.8 2000 Exposed Locations 105.6 156.6 252.0

Reference Locations 62.8 7.9 20.5 2002 Exposed Locations 60.3 9.8 13.2

* Values shown are the 95% UCL of the mean. **The concentration listed is influenced by a single value of 1130 ppb, 95% UCL of the mean excluding that value equals 53.9

ppb (dw)

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1.0 INTRODUCTION This document is the Final Risk Assessment (FRA) report on the evaluation of ecological and human

health risks associated with the mercury spill that occurred on June 2, 2000 near the towns of San Juan,

Choropampa, and Magdalena, in Northern Peru. The methodology utilized in assessing the potential risk is

consistent with the approach that was presented to the Ministry on January 24, 2001, and as established

with the independent reviewer, Dr. Peter M. Chapman of EVS Environment Consultants, North

Vancouver, Canada.

1.1 Project Background

The purpose of this report is to provide an assessment of the potential risks to humans and the

environment from the spill of elemental mercury (Hg) that occurred on June 2, 2000 in Northern Peru.

The spill occurred as the mercury, a minor product of mining at the MYRSL facility, was being

transported on a truck owned by the transport company RANSA (contract carrier for MYSRL) from the

mining operations to Lima. An extensive account of the spill can be found in the Mercury Spill Incident

Report (MYSRL 2001). For the purpose of this report, only a brief summary of the spill response is

provided.

The spill occurred during transport of the mercury from the mine to Lima along the road between

Cajamarca and the Pan American highway (Map 1). At approximately Km 155, a chlorine gas cylinder

became dislodged from the trailer and disrupted the mercury containers such that they were knocked loose

from their original positions, and several were inverted. Elemental mercury began to spill in the area of

Km 155 and subsequently along the route of travel until the truck parked in Magdalena later in the evening

of June 2. MYSRL first received word of the spill on the morning of June 3rd and immediately started to

respond. Initial response efforts included identifying the spill locations and working with local agencies to

inform the public about the potential hazards of possessing and handling the spilt mercury. Subsequent

efforts focused on addressing the potential health risks associated with the collection of the spilt mercury

by local citizens, as well as further identifying spill locations and cleaning-up the spilt mercury.

The initial response efforts detailed 16 distinct spill locations (Map 1) where visible mercury was identified.

Upon identification of spill areas, clean-up was initiated at these locations, with all visibly contaminated

material (roadside soil and asphalt) removed and transported to the heap leach pile at the Maqui Maqui

Mine. Unfortunately, prior to identification and clean up of all locations, some of the mercury was

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collected by residents, primarily in Choropampa, and taken to homes. Upon learning of the residential

collection of mercury, MYSRL undertook a program to recover mercury from the local citizens and

initiated public education regarding the health risks associated with mercury. These programs were

conducted in cooperation and coordination with local and regional governmental and health care agencies.

Later surveys identified additional areas where visible mercury was not present, but where elevated

mercury levels required remediation.

Determining the success of the recovery of mercury during the remediation effort was evaluated using a

mass balance approach. Upon completion of the recovery activities, final mass balance calculations were

performed by MYSRL and by an independent auditor (MYSRL 2001). Using two very separate

approaches, both of the calculations determined that only six to nine Kg of mercury likely remained in the

environment or in the possession of local citizens after the completion of clean-up activities. This indicates

that greater than 94% of the mercury was successfully removed from the immediate environment around

the spill. The remaining mercury is likely widely dispersed in the environment or in the possession of local

citizens.

1.2 Mercury

1.2.1 Introduction

Mercury is the seventh metal of antiquity and has been known and used by mankind for over 3500 years,

including gold mining by the Romans (Meech et al. 1998). Uses of mercury throughout time have included

both industrial and ‘medicinal’ applications. Mercury has been used as a fungicide, as a slime control

agent, and in various manufacturing processes, including the production of chlorine (chloralkali plants) and

sodium hydroxide (Eisler 2000, Meech et al. 1998). The inorganic form of mercury has historically, but not

presently, been used as an antiseptic, a disinfectant, a purgative, a counterirritant, and when dissolved in oil

of vitriol (sulphuric acid) and distilled with alcohol, as a cure for syphilis (Veiga and Meech 1995). The

potential for mercury toxicity was first reported in 1533 by the famous Swiss physician Paracelsus, in a

book on occupational diseases, in which he discussed Hg poisoning of miners (Veiga and Meech 1995).

Mercury naturally occurs in the environment and cycles through the Earth’s atmospheric, water, and

terrestrial components (Figure 1.2.1). The total global annual input of mercury to the atmosphere is

estimated to range from 900 to 6200 metric tons (0.9-6.2 million Kg). This includes input from both natural

and anthropogenic (i.e., human caused) sources (Chu and Porcella 1995, USEPA 1997a). Natural

releases of mercury to the environment occur as gases (vapor emission from natural ores), as solutions

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(e.g., in lava), or as particulates (e.g., dust). The global cycling of mercury involves atmospheric transport

(primarily as elemental mercury vapor) of mercury that has degassed from the earth’s crust and from

evasion (evaporation) of mercury from water bodies. Some of the elemental mercury vapor is oxidized to

form ionic mercury (Hg+2), which is then re-deposited onto land and water surfaces, primarily as a

particulate. The estimated residence time, or the average time that an evaporated mercury particle is re-

deposited from the atmosphere to the earth’s surface, is one year (Eisler 2000, Porcella 1994).

Human activity has caused large increases in the concentration of mercury in different environmental

media (Hylander 2001, USEPA 1997a). It is estimated that atmospheric depositional rates have increased

by a factor of 3.7 since 1850. River sediment concentrations are reported to have increased fourfold, and

lake and estuarine sediments two to fivefold, since pre-cultural times. Currently, it is estimated that in the

United States alone, 100 to 158 metric tons of mercury (100,000-158,000 Kg) are released to the

atmosphere each year, primarily from the burning of fossil fuel (e.g., coal) and from industrial factories

(Chu and Porcella 1995, USEPA 1997a). A single medium to large-sized coal power plant emits 114 Kg of

Hg per year via the smokestack and another 23 Kg from cleaning of the coal (NWF 2000). Overall, fuel

combustion (primarily coal) results in 54% of the annual global Hg emissions (Hylander 2001).

Humans also release mercury to the environment through industrial processes and from artisanal

(rudimentary) precious metal mining. Mercury is utilized in more than 2000 manufacturing industries and

products (Jones and Slotton 1996). Operation of chloralkali plants, to produce chlorine and caustic soda, is

one of the largest industrial emitters of mercury. Chloralkali plant emissions are thought to produce 90%

of the anthropogenic releases of mercury in Europe (Hylander 2001). In Latin America, artisanal mining

with mercury amalgamation is a major source of mercury to the environment, with an estimated 200

tonnes (200,000 Kg) of Hg released annually as a result of these activities (Veiga et al. 1999). While

there is current artisanal mining in Peru, there is no known artisanal mining ongoing in the Jequetepeque

watershed.

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Figure 1.2.1 Global cycling and fluxes of mercury (from USEPA 1997a)

Mercury is mined as a primary product, or as a byproduct of other metal mining. Mine production in 1999

was 2100 tonnes, with Algeria, Kyrgyzstan, and Spain as the largest producing countries (USGS 2000). A

single mine, the Almaden mine in Spain, produced 860 tonnes in 1997. This mine has been in nearly

continual production for the last 2000 years, and is the largest known deposit of mercury (Lindberg et al.

1979). As a single source of emissions to the atmosphere, the Almaden mine emits 0.5 to 1 Kg of

mercury per hour.

Humans and other biota are exposed to mercury from both naturally-occurring levels in the environment

and from releases due to the burning of fossil fuels and industrial releases. Humans are also directly

exposed to mercury from the use of mercury in dental fillings. Exposure from dental work is more

common in the industrial world due to wider availability of dentistry. As an example, it has been estimated

that an average citizen of Sweden has 10 g of mercury in their body as a result of dental work (Hylander

2001).

1.2.2 Environmental Cycling

The cycling of mercury in the environment is complex, with toxicity and movement of environmental

mercury highly dependent on the chemical form present. The primary chemical forms of mercury in the

environment are: elemental (Hg0), ionic mercury (Hg+2 and Hg+1), and organometallic, primarily in the

form of methylmercury (HgCH3).

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Global Cycling

Elemental mercury is the most common form in the atmosphere (Figure 1.2.1). Over time, a small amount

of this mercury is oxidized to become the ionic Hg+2 form, which is subsequently deposited into surface

soils and waters. Ultimately, this deposited mercury is converted to the essentially insoluble HgS

(cinnabar) form (Jones and Slotton 1996). Estimated residence times for mercury are up to one year in

the atmosphere and 1000 years in soils (Eisler 2000). The predominant form of mercury in aquatic

environments is mercuric ion (Hg+2), which can bind firmly to sediments, or under appropriate conditions

can be reduced to elemental mercury and lost to the environment via vapors, or microbially converted to

methylated mercury (Lorey and Driscoll 1999).

Except for volatilization of the elemental form, both elemental and ionic mercury are largely immobile in

the environment (Battelle and Exponent 2000, Kabata-Pendias and Pendias 1992). In general, elemental

mercury is very insoluble and ionic forms are only slightly more soluble (Table 1.2.1), which limits the

movement of mercury in the environment.

Table 1.2.1 Example Solubility of Some Forms of Mercury

Chemical Form Hg Species Solubility (ug Hg/ml water*)

Elemental Hg0 0.056 HgCl2 Hg+2 74,000 HgO Hg+2 51.6 HgS Hg+2 insoluble-0.013 Hg2Cl2 Hg+1 2

* Data from Davis et al. 1997

As an example of the limited mobility of mercury, at a site where sewage sludge was applied for twenty

years, the mercury contained in the sludge did not move past the top 15 cm of the soil profile (Granato et

al. 1995). Since mercury will not readily migrate through the soil column, the degree to which plant roots

will be exposed to increases in mercury concentrations at the soil surface is limited. Furthermore, plants

have a low affinity (i.e., uptake) for mercury. This is largely a result of low solubility, as well as strong

affinity of the dissolved forms of mercury (i.e., Hg+2) binding strongly to soil organic matter and clays, thus

further limiting the availability to plants (Hempel et al. 1995). Researchers have found that large increases

in soil mercury concentrations result in only slight increases in plant tissue mercury concentrations (Patra

and Sharma 2000). The limited amount of mercury that is absorbed by plants is largely retained in the

roots, and is not transferred to stems and leaves that could then be eaten by herbivores (i.e.,

livestock)(Granato et al. 1995). The greatest concern with mercury in the environment is typically

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reserved for methylmercury, due to its greater toxicity and its ability to build-up to high levels in aquatic

food-chains (Clarkson 1994). Methylmercury is uncommon in terrestrial soils and ecosystems since the

conditions amenable to methylation are not present in these systems (Davis et al. 1997).

Local Cycling

Over time, the elemental mercury that was spilled in Northern Peru will be transformed into ionic forms

(likely HgO and HgS) in the environment. Solubility and transport may increase, especially for the

mercury-oxide complexes (Figure 1.2.2). The uptake rates of ionic mercury into plants will be higher, as

will the absorption of mercury into animals that eat the plants or soil. Even after elemental mercury has

been converted into ionic forms, however, soil microorganisms can re-convert Hg+2 (e.g., HgO) back to

elemental mercury, which can then evaporate from the soil to the atmosphere (Kim et al. 1997).

Figure 1.2.2 Local cycling of the spilt mercury Due to the generally steep terrain in the Jequetepeque watershed and movement of surface particles

through erosion, the ultimate fate of mercury remaining from the spill (i.e., not removed by clean-up

activities), and that does not evaporate to the atmosphere, will likely be the Gallito Ciego reservoir, via the

Jequetepeque River. Once transported to surface water, some of the mercury bound to soil particles may

dissolve. The dissolved mercury, primarily in the Hg+2 form, should be fairly evenly distributed in the

water column. Mercury associated with soil particles that have eroded and been transported in the water

column to the reservoir will likely preferentially drop out at the river-reservoir interface, as evidenced by

the extensive depositional zone at the mouth of the reservoir. Overall, in order for the spilt elemental

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mercury to be accumulated in food-chains, it must first be rendered soluble (i.e., oxidized into ionic

mercury) and then converted into methylmercury (Meech et al. 1998).

Methylation and Aquatic Systems

Mercury in aquatic environments is typically dissolved mercuric ion (Hg+2). Over time, the dissolved ionic

mercury can be bound up in sediments, can be reduced to elemental mercury and lost to the atmosphere,

or can be converted to organic mercury (i.e., methylated) in the sediment. Methylmercury in lakes can

also come from precipitation in heavily contaminated industrial areas (Rudd 1995). Phytoplankton (algae)

can reduce ionic Hg to elemental Hg at the rate of 0.5%-10% per day, increasing the loss of mercury to

the atmosphere and reducing the amount of mercury in aquatic systems available for potential methylation

(Mason et al. 1995).

The uptake of mercury into aquatic biota is strongly influenced by water chemistry. Ionic mercury (Hg+2)

in the water column can interact with S-2 (sulfide) if present, forming an essentially insoluble HgS

precipitate, which is unavailable to biota. Sulfide levels are influenced by pH and redox conditions in the

water. As such, aquatic systems with higher pH (>7.0) or lower redox potentials tend to have less

potential for mercury accumulation in aquatic biota. High calcium, zinc, and selenium concentrations in

water also can reduce mercury uptake into aquatic biota (Bjornberg et al. 1988). Selenium has also been

shown to be protective, or reduce the effects of mercury, to aquatic biota (Eisler 2000). Generally, ionic

mercury (Hg+2) does not bioaccumulate to a significant degree in aquatic systems (Jackson 2001, Laporte

et al. 2002). Because of this, the amount of methylation that occurs is important for determining the risk to

aquatic systems.

The mercury associated with sediments can undergo methylation if appropriate conditions exist. Elemental

mercury cannot be directly transformed into methylmercury, but must first be oxidized (Meech et al. 1998,

Veiga 1997). Production of methylmercury is controlled by the mercury complexing characteristics, the

microbial metabolic activity, and the total inorganic concentration in the sediment (Hintelmann et al. 2000,

Rudd 1995). Methylation of mercury is favored where there are humus or peat sediments (i.e., high

organic matter) and anoxic conditions. This explains why fish tissue levels of methylmercury increase in

newly created lakes since soils with organic matter (i.e., humus) are placed under saturated (i.e., anoxic)

conditions (Morrison and Thierien 1995, Porvari and Verta 1995). Essentially no methylation occurs under

aerated conditions (Porvari and Verta 1995).

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In general, lower pH waters tend to liberate more methylmercury from sediments into water than higher

pH waters. Methylmercury released to the water column can be incorporated into aquatic biota. High

fulvic acid waters will also result in more methylmercury being released from the sediment to the water

column, primarily by increasing mercury solubility (Veiga 1997). Darkwater rivers (i.e., the Amazon)

result in higher methylmercury levels in fish than corresponding Hg in whitewater rivers due to the

presence of fulvic acids (Meech et al. 1998). In lakes, seasonal stratification of the water can create an

anoxic hypolimnion (i.e., oxygen-free zone), which can induce spikes in methylmercury production

(Slotton et al. 1995).

1.2.3 Typical Background Mercury is widely distributed in the environment, with concentrations present in all waters, soils, and in

every living organism (Clarkson 1994). Due to industrialization, mercury levels in the environment have

increased over the past 40 years, though atmospheric concentrations appear to be stable, if not declining,

due to recognition of the problem and implementation of controls for limiting mercury dispersal (Hylander

2001). Typical conversion factors and units for mercury in the environment are provided in Table 1.2.2

Table 1.2.2 Typical Units and Conversions

Media

Typical Units

Equivalent Units

water ug/L ppb soil mg/kg ppm vegetation ug/kg ppb animal tissue u g/kg ppb

Conversions

ppm to ppb 1 ppm 1000 ppb ppb to ppm 1 ppb 0.001 ppm

Mercury naturally occurs in all components of the environment. On average, mercury is present in the

earth’s crust at 500 ppb on a dry weight (dw) basis. The mercury concentration in rainwater ranges from

0.001 ppb in remote non-urban areas up to 3.5 ppb in urban areas. Forest fires and rain are responsible

for the majority of mercury deposition onto the world’s surface waters and soils (Fergusson 1990, Hall

1995, Jones and Slotton 1996). The Geological Survey of Canada collected 1684 soil samples throughout

Canada and measured mercury concentrations. The reported mercury concentrations in these samples

ranged from 2 to 1530 ppb (dw), with a geometric mean of 60 ppb (Richardson et al. 1995). Kabata-

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Pendias and Pendias (1992) report that the concentrations of mercury in uncontaminated soils from around

the world range from 4 ppb (Sweden) to 5800 ppb (Russia), with typical mean soil values for different

countries of approximately 200 ppb (dw). Shales typically contain up to 3200 ppb (dw) and coal up to

8500 ppb (dw) mercury, with mercury sulfide being the most commonly occurring form in coal (Adriano

1986). Surface water concentrations of mercury vary greatly, but reported values are usually less than 0.5

ppb (Bjornberg et al. 1988, Irwin 1997a).

Mercury also naturally occurs in food items. Typically reported mercury concentrations in terrestria l

plants range from 30-700 ppb (dw). The reported average concentration of mercury in wheat from the

United States is 290 ppb (dw) (Adriano 1986). The highest concentrations of mercury in food are

generally reported for fish and shellfish. Concentrations in food items from different countries are shown

in Table 1.2.3. There is a large degree of variability in observed tissue concentrations of mercury, even

for the same type of food.

As estimated by Richardson et al. (1995), the total human intake of mercury in Canada is 7.7 ug/day, or

0.11 u g of Hg per Kg of body weight per day (ug/Kg-day). The absorbed dose was estimated to be 5.3

ug/day, or 0.076 ug/Kg-day. Only the absorbed dose can cause toxicity in humans or animals. The non-

absorbed dose is excreted, primarily in the feces. It was determined that fish consumption accounted for

27% of the mercury intake and 40% of the absorbed dose. Dental work accounted for 36% of intake and

42% of absorbed dose. The dose from food, other than fish, is primarily from intake of Hg+2, which has

much lower absorption in the gastrointestinal tract. The dose from the rest of the diet (i.e., non-fish) was

estimated at be 1.82 ug/day with the absorbed dose only 0.18 ug/day. In a study of the Swedish diet, the

estimated mercury exposure from the diet ranged from 1 to 30.6 ug/day (Underwood 1977).

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Table 1.2.3 Ranges of Mercury Concentrations in Diets in the U.S.A., Canada, Scotland, Italy, and Spain

Food Type and Item Range* (ppb)

Meat

Beef liver 2-30 Meat and poultry <2-7 Viscera <2-80 Other meats (lamb, pork, hare) 2-3 Wild fowl (muscle) <126-242 Can. goose (muscle) <30-135 Ducks (muscle) <23-704 Ducks (liver) 16-3800

Fish and shellfish

Canned fish 135-612 Frozen Fish 6-736 Shrimp 28 Various fresh fish 30.5-1082 Shellfish 6-490

Vegetables

Various 1-18

Grains

Bread/pasta/cereal 4-33.4

Fruit

Various- citrus/berries 1.3-5.6

Eggs

Chicken/domestic <2-5 Waterfowl eggs <60-500

Other

Sugar/condiments <2-6 Dairy- milk,cheese <2-22.6 Nuts <2-19 Beverages <2

*data sources: USFDA (1999), MAFF (1997), MAFF (1994), Environment Canada (1999), Ristori and Barghigiani (1994) and Urieta et al. (1996); values listed are for food as consumed in the diet

Mercury concentrations in fish are of great interest to health professionals since fish contribute much of

the mercury dose to humans. There is a high degree of variability in typical concentrations of mercury in

fish. Some of the factors influencing fish tissue mercury concentrations include: fish type and age, water

chemistry, and concentration of mercury in water and sediment. Sweet and Zelikoff (2001) reported that

fish from uncontaminated areas had mercury concentrations that ranged from 18 to 600 ppb (ww). Shilts

and Coker (1995) reported that fish collected in a remote Arctic area of Canada, that is not influenced by

any nearby mercury emissions, had mercury tissue levels of 570-2200 ppb (ww). These seemingly

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elevated levels were determined to be related to high natural backgrounds of mercury associated with the

presence of sulphide mineralizations in the area. As humans have decreased concentrations of mercury

released to the environment in some locations, the measured concentrations of mercury in fish have also

decreased. (Winstanley 1999).

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2.0 RISK ASSESSMENT PROBLEM FORMULATION Risk assessment (RA) is a procedure for making environmental decisions based on the evaluation of

possible effects of an activity (i.e., spill) to the environment and to human health. The risk assessment

process can determine if a chemical release, in this case a mercury spill, has contaminated or polluted an

area. Contamination is defined as the presence of a chemical in excess of natural conditions but below

biologically available concentrations that result in risk, whereas pollution is defined as contamination

causing adverse biological or health effects. The USEPA (1998) outlines three primary steps in

conducting a risk assessment: 1) Problem Formulation, 2) Risk Analysis, and 3) Risk Characterization.

Problem Formulation is the planning phase of a RA, in which the goals, scope, focus, and analysis plan are

formulated. The plan developed in the Problem Formulation is implemented in the Risk Analysis phase.

The Risk Characterization phase then documents the analysis and integrates the results to describe overall

risk. In brief, the risk assessment process utilized involved a process of gathering information, through

sampling, on the concentrations of mercury in the environment and comparing these measured

concentrations to benchmark effect concentrations for both humans and applicable biota. The exposure

pathways and receptors are outlined in the conceptual model of the site (Section 2.3), which is based on

the fate and transport of mercury in the environment and characterization of the ecosystems in the spill

area. Benchmark values are discussed in Section 3 and the measured exposures are discussed in Section

4 of this report.

2.1 Identification of Contaminants of Potential Concern (COPCs) The mercury spilt was essentially pure elemental mercury that is recovered as a by-product of the milling

process at the MYSRL facilities. While only mercury was spilled, the collected mercury was analyzed to

confirm that there were no other chemical constituents in the mercury that might pose risk to the

environment. The analysis found that the mercury was essentially pure, with only trace amounts of other

inorganic chemicals present. In order to verify that none of these trace inorganic constituents in the

mercury would need to be evaluated in the risk assessment, the results of the chemical analysis were

compared to guidance values. Additional inorganic constituent concentrations in the mercury were

verified to be less than U.S. Environmental Protection Agency (USEPA) soil screening levels (SSLs) and

risk based screening levels for residential soils (Table 2.1.1; USEPA 1996, 2001d). While there are no

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guidance values for four of the inorganic constituents (bismuth, gallium, gold, and strontium), the

concentrations of these constituents are low and none of them are generally considered to be an

environmental or human health concern (Amdur et al. 1991, Irwin 1997b).

Table 2.1.1 Evaluation of Trace Constituents in MYSRL Mercury

Mercury Benchmark Values Trace

Constituent Sample 1 (mg/Kg)

Sample 2 (mg/Kg)

SSL1 (mg/Kg)

Residential 2 (mg/Kg)

Exceed safe values

Aluminum 2.24 2.08 78000 N Antimony <0.057 <0.057 31 31 N Arsenic <0.29 <0.29 0.4 0.43 N Barium 0.078 0.067 5500 5500 N Beryllium <0.005 <0.005 0.1 160 N Bismuth <0.005 0.061 NA Boron <4.15 4.5 7000 N Cadmium 0.009 <0.005 78 78 N Chromium <0.05 <0.05 390 230 N Cobalt 0.004 0.004 4700 N Copper 0.33 0.19 31000 N Gallium 0.041 0.057 NA Gold 1.62 1.69 NA Iron 15.7 14.7 23000 N Lead 0.322 0.275 400 N Lithium <0.003 <0.003 1600 N Manganese 0.11 0.05 1600 N Molybdenum <0.04 <0.04 390 N Nickel 0.03 0.02 1600 1600 N Selenium 22 7.9 390 390 N Silver 102 35.8 390 390 N Strontium 0.084 0.068 NA Thallium 2.01 1.99 5.5 N Tin 0.12 0.08 47000 N Titanium 0.1 <0.05 310000 N Vanadium <0.62 <0.62 550 550 N Zinc 0.09 0.15 23000 23000 N NA= no applicable guidance values 1 USEPA (1996); values listed are safe levels for human consumption of soil 2 USEPA (2001d); values listed are safe levels for residential soils

2.2 Site Description and Ecological Resources This report assesses potential risk from mercury to human and ecological receptors in the upper portion of

the Jequetepeque watershed, located in the District of Magdalena, Province and Department of

Cajamarca. The overall watershed is large, covering a distance of 160 Km and a total area of 623,220 ha

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(Cabanillas 1998), with the headwaters in the Central Cordilleras, and the terminus at the Pacific Ocean.

This report, however, only focuses on a portion of the upper watershed, specifically, the area between Km

155 and the Gallito Ciego Reservoir (approximately Km 52; see Map 1).

The ecology of the area is summarized by Cabanillas (1998) and Bazan et al. (2000). The specific area of

interest for this assessment ranges from approximately 2500 m above mean sea level (amsl) at Km 155 to

450 m amsl at the Gallito Ciego Reservoir. A wide variety of vegetation communities occur within this

area, including Montane Tropical Humid Forest, Lower Montane Tropical Dry Forest, Pre-montane

Tropical Dry Forest, Pre-montane Tropical Thorny Slopes, and Tropical Desert Shrub (Cabanillas 1998).

The overall assessed area, however, is largely limited to the Lower Montane Tropical Dry Forest and

Tropical Desert Shrub communities.

The climate of the region varies significantly with elevation. As an example, San Juan, at an elevation of

2300 m (amsl) recorded 876 mm of rainfall during 1982-83, whereas Tembladera, at 450 m (amsl), only

received 100 mm over the same time period. Yearly variability in rainfall is substantial, and is reflected in

the flow of the Jequetepeque River. Over the time period 1977 to 1993, the recorded annual flow at the

Yonan recording station ranged from 105 million cubic meters in 1980 to 1947 million cubic meters in 1984.

The annual average flow over this time period was 698 million cubic meters (Cabanillas 1998).

Except at the highest elevations in the watershed, the land has been extensively modified by the human

inhabitants. At higher elevations, wheat and corn are the primary cultivated species, with non-cultivated

land utilized as grazing areas for cattle, goats, and sheep. Further down-valley, sugarcane and rice are

more common, though corn, banana plantations, and mixed-vegetable gardens are also prevalent.

Furthermore, many varieties of fruit (e.g., mango and lemon) are grown, especially near houses for

personal consumption. An extensive network of irrigation canals, that primarily utilize seeps and tributaries

of the Jequetepeque, are employed to irrigate the cultivated crops.

Due to the long history of human inhabitation of the watershed, larger wildlife are not common in the spill

area. Smaller mammals and birds, however, are observed and are likely to occur in much greater densities

than larger animals. From reviews by Eisenberg and Redford (1999) and Bazan et al. (2000), mammals

that have been observed in areas near the spill, or are native to the broader region, are shown in Table

2.2.1. Mammal families are listed, along with an estimate of the likelihood of occurrence near the spill

area. The likelihood of occurrence is based on 1) distribution maps provided by Eisenberg and Redford

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(1999), 2) observations on habitat made during the field investigations, and 3) conversations with MYSRL

personnel and the local population. Where possible, if members of a particular mammal order are likely to

occur, or may possibly occur, representative genus and common names of the mammals are listed as well.

Table 2.2.1 Mammal Orders and Likely Occurrence Near the Spill Area

Order Common name In area? Genus represented Common names

Marsupialia Marsupials possible Didelphis spp. opossum Edentata Anteaters unlikely

Armadillos unlikely Insectivora Insectivores unknown Chiroptera Bats likely Glossophaga spp long-tongued bats

likely Pteronotus spp mustached bats likely Tonatia spp round-eared bats likely Myostis spp little brown bats likely Chiroderma spp large-eyed bats likely Sturnina spp yellow-shouldered bats likely Vampyressa spp yellow-eared bats

Primates Monkeys, apes, humans yes Homo sapiens humans Carnivora Carnivores possible Pseudolopex culpaeus South American fox

possible Mustela frenata long-tailed weasel possible Felis colocolo gato de pajonal possible Felis concolor mountain lion possible Conepatus semistriatus hog-nosed skunk

Perissodactyla Odd-toed ungulates unlikely Artiodactyla Even-toed ungulates possible Odocoileus virginianus white-tailed deer Rodentia Rodents likely Thomasomys spp rat

likely Microryzomys spp rat likely Oligoryzomys spp rat yes (domestic) Cavia tschudii cuy (guinea pig) likely Lagidium peruanum big chinchilla

Lagomorpha Rabbits yes (domestic) Oryctolagus spp domestic rabbit

Bazan et al. (2000) lists species of raptors, dabbling ducks, grebes, and shorebirds that are known to

inhabit areas near the spill. Bird species that were observed in the area during site visits were: wild

canaries (Sicalis spp.), vermilion flycatcher (Pyrocephalus rubinus), groove-billed ani (Crotophaga

sulcirostris), and other unidentified small songbirds (Order Passiformes) and herons.

Table 2.2.2 shows the species of fish known to occur in the Jequetepeque River and the Gallito Ciego

Reservoir. The occurrence of these species was determined by sampling work conducted to support the

risk assessment and from interviews with local fishermen. All of the species listed in Table 2.2.3, except

paco and tilapia, occur in both the reservoir and the river. Paco and tilapia were only collected in the

reservoir and did not occur in the river. Overall, the life history of the native fish species in the watershed

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(i.e., all species except tilapia) are not well characterized in the scientific literature. As an example, some

individual fish collected during sampling are larger than what the literature indicates as the maximum

length for that species.

Table 2.2.2 Fish Species in the Jequetepeque River and Gallito Ciego Reservoir

Peruvian

Name

Common

Name

Scientific Name

Family

Family

common name

Diet

Habitat

Lit. Max

Length (cm)

Site length range (cm)

Cachuela Carachita Bryconamericus peruanus

Characidae Characins Omnivorous benthopelagic, freshwater

2-10

Cascafe (Sabalo) Brycon atrocaudatus

Characidae Characins Plants and zooplankton

pelagic, freshwater 40 3.7-33

Charcoca Twospot lebiasina

Lebiasina bimaculata

Lebiasinidae Characins Insects pelagic, freshwater; 6.2 <pH< 7.5

10 3.5-13.5

Life catfish Trichomycterus dispar

Tricho-mycteridae

Pencil/ parasitic catfishes

Detritus benthopelagic, freshwater

8-17.8

Mojarra Green terror

Aequidens rivulatus Cichlidae Cichlids Plants and invertebrates

benthopelagic, fresh-water; 6.5<pH< 8.0

20 3.1-21

Nato life catfish Astroblepus rosei Astroblepidae

Climbing catfishes

Insects and algae

demersal, freshwater

3.1-14

Paco Pirapatinga Piaractus brachypomus

Characidae Characins Insects and decaying plants

pelagic, freshwater; 4.8<pH< 6.8. An important foodfish

45 7-8

Pejerrey Pejerrey Odontesthes bonariensis/regia

Atherinidae Silversides Plankton and insects

pelagic, freshwater, brackish, marine

23.4 4.5-20

Picalon catfishes Pimelodella yuncensis

Pimelodidae Long-whiskered catfishes

Algae demersal, freshwater

4.8-10

Tilapia Blue Tilapia (Introduced)

Oreochromis aureus

Cichildae Cichlids Plankton Inhabits warm ponds and impoundments as well as lakes and streams. demersal, freshwater, brackish

37 13-30

All of the fish species that occur in the watershed (Table 2.2.2) are either herbivorous (plant eaters) or

omnivorous (eat both plant and animal matter). There are no identified higher-trophic order piscivorous

fish (fish that eat fish) in the river or reservoir. Piscivores are known to have the greatest potential for

accumulating mercury (Uryo et al. 2001).

2.3 Conceptual Site Model: Fate, Transport, and Potential Exposure Five systems are at potential risk from the spilt mercury: agricultural, native terrestrial, residential, riverine,

and the reservoir ecosystems. Residential is included as a system type since some of the mercury spill

sites (Map 1) occur within towns. Biota in these towns, including domestic animals and garden plants,

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were potentially exposed to mercury. Other general receptor types within the terrestrial systems are

humans, wildlife, and plants (agricultural and native). The conceptual exposure pathways and fate and

transport of mercury in the terrestrial ecosystems are shown in Figure 2.3.1. Possible receptors within the

aquatic ecosystems include fish and aquatic macroinvertebrates. The conceptual exposure pathways and

fate and transport of mercury in the aquatic ecosystems are shown in Figure 2.3.2.

Conceptually, mercury is initially in the form of elemental mercury. Elemental mercury can volatilize, be

mobilized via wind or water transport, or be oxidized to form Hg+2. Over time, much of the elemental

mercury will be oxidized, thus converting the mercury to ionic forms. For ionic mercury, the volatilization

rate substantially decreases, while the water solubility increases slightly. Ionic mercury does bind strongly

to soil particles, but over longer time periods, it may be transported into streams through erosion of surface

soils or by limited dissolution. If appropriate reducing conditions exist (see Section 1.2.2), mercury that

enters the surface water may be methylated. Methylmercury has much higher availability to organisms,

thus increasing the potential for mercury bioaccumulation in biological tissues.

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Figure 2.3.1 Conceptual site model of mercury transport and potential receptors in the terrestrial ecosystems

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Figure 2.3.2 Conceptual site model of mercury transport and potential receptors in the aquatic ecosystems

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2.4 Assessment and Measurement Endpoints

The overall management goal for the spill area is:

Protecting the terrestrial and aquatic resources of the Jequetepeque watershed that were

potentially exposed to mercury contamination from the spill.

Assessment endpoints are explicit expressions of the actual environmental values that are to be protected

within the overall management goal (USEPA 1998). The assessment endpoints for the risk assessment

are:

1. Health of individual humans who may consume water and food that may be influenced by the mercury spill.

2. Survival, growth, and reproduction of populations of agricultural and native terrestrial plants that are within the spill area.

3. Survival, growth, and reproduction of populations of terrestrial animals that may be exposed to mercury from drinking water, consumption of plants, or consumption of other animals.

4. Survival, growth, and reproduction of populations of aquatic biota (macro-invertebrates and fish) that may be exposed to mercury from the spill.

The USEPA (1998) identifies three types of measures that are used to evaluate the assessment endpoints

and to assess the risk potential:

n

Measures of Effect – Direct measures of changes in an attribute of the assessment endpoint that can be attributed to exposure to the chemical in question.

n Measures of Exposure – Measures of chemical concentrations and movement in the

environment.

n Measures of Ecosystem and Receptor Characteristics – Measures of ecosystem and

receptor characteristics that influence the potential for contact between the receptors and chemicals.

No direct site-specific measures of effect were made. The measures of effects used in the risk

assessment are benchmark effect concentrations issued by various regulatory groups or values derived

from the scientific literature. These benchmark values are discussed in Section 3. Extensive direct

measures of exposure were collected through sampling of terrestrial and aquatic media and biota.

Sampling included water, sediment, soil, vegetation, terrestrial insects, aquatic macroinvertebrates and fish.

For the exposure assessment of the consumption of terrestrial animal tissue, which was not directly

sampled, mercury transfer from the measured vegetation tissue to herbivore tissue was modeled using

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literature transfer factors. The various measures of exposure are discussed in Section 4. There were no

direct measures of ecosystem and receptor characteristics. The assessment endpoints and associated

measurement of effects and measures of exposure are summarized in Table 2.4.1.

Table 2.4.1 Summary of Assessment Endpoints and Measures of Effect and Exposure

Assessment Endpoint Measures of Effect and Exposure









Survival, growth, and reproduction of populations of terrestrial animals that may be exposed to mercury from drinking water, consumption of plants, or consumption of other animals





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3.0 EFFECTS CHARACTERIZATION AND BENCHMARK SELECTION Regulatory guidance values and the scientific literature were reviewed and summarized for measures of

effects. As outlined in Section 2.3, terrestrial receptors are plants (agricultural and native), livestock,

rodents, birds, humans, and other secondary consumers (e.g., fox). Receptors at potential risk from

pathways that start with water exposure are: aquatic macroinvertebrates and fish, as well as secondary

consumers of aquatic biota, including humans and birds. Terrestrial animals and birds may also utilize

surface water as a source of drinking water.

The literature was surveyed for concentrations of mercury that were reported as 1) resulting in no adverse

effects or 2) resulting in an adverse effect. The no adverse effect concentrations are termed NOAELs,

short for no observed adverse effect levels. Concentrations that result in an effect are called Effect

Levels. NOAEL concentrations are sometimes reported as safe levels, no effect levels, threshold

concentrations (i.e., the threshold before effects are observed), or normal levels. Commonly reported

Effect Levels are 1) the lowest observed adverse effect level (LOAEL), 2) specific effects on growth or

reproduction, or 3) lethal concentration (LC). While both NOAEL and Effect Levels are summarized in

this section, the RA relies on the more conservative NOAEL values to assess the risk potential. The

literature survey focused on finding information on species relevant to the receptors identified in Section

2.3. Additionally, effort was made to locate and summarize papers that discussed long-term exposures

and reported non-lethal effects from relevant exposure routes (e.g., ingestion rather than injection).

Reports that provide information on the effect, or lack of effect, of mercury on growth and reproduction of

receptors are more desirable than studies that provide lethal concentrations.

3.1 Mercury Toxicity to Humans and Benchmark Determination Possible effects and manifestations of mercury intoxication to humans, and other animals, are varied.

Effects depend on the chemical form of the mercury, the exposure route (inhalation or ingestion), and the

exposure dose, including the length of exposure and concentration of mercury involved (Amdur et al.

1991). For residents around the spill, the primary possible exposure routes are 1) the inhalation and

ingestion of the spilt elemental mercury, and 2) the ingestion of ionic mercury after oxidation of the spilt

elemental mercury has occurred. Additionally, if the spilt mercury enters waterways around the spill areas

over time, humans may be exposed to methylmercury through consumption of aquatic organisms that

might be influenced by the increased mercury concentrations in surface water and sediment.

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Methylmercury exposure from consumption of terrestrial plants and animals is unlikely because

methylmercury is uncommon in soils, due to the lack of reducing conditions required to methylate mercury

in soils (Davis et al. 1997).

Inhaled elemental mercury vapor is distributed to the entire body (systemic), whereas ingested mercury is

first cycled through the liver, which is an important detoxification site, prior to systemic distribution.

Ingestion of elemental mercury is generally not considered a health risk since it is largely passed directly

through the gastrointestinal tract, with little absorption, and is excreted in feces, therefore limiting the

amount of mercury that enters the body. Inhaled elemental mercury, conversely, readily crosses the

alveolar membrane of the lung since it is lipid soluble, and is therefore absorbed to a much greater degree.

Mercury absorbed in the body, via ingestion or inhalation, is excreted with a half-life (i.e., time required to

reduce the concentration in the body by 50%) of 35 to 70 days (Amdur et al. 1991, WHO 1991).

Elemental mercury is not listed as a known carcinogen by the U.S. EPA (USEPA 2001b).

As discussed in Section 2.4, the spilt elemental mercury will be transformed to ionic forms over time.

Effects from acute ingestion of ionic mercury include ulcers and other gastrointestinal effects. Chronic

exposure can result in kidney damage, which can be manifested as changes in urine production or in a

build-up of urea in the blood (Amdur et al. 1991, USEPA 2001b). There is also limited evidence that

chronic exposure may effect fertility, likely through effects on sperm production. These effects, however,

were only evidenced after large acute exposures in mice, and fertility returned to normal levels within

about two months (USEPA 2001b, WHO 1991). Ionic mercury is not listed as a known carcinogen

(USEPA 2001b, WHO 1991).

Due to the rapid remediation response and strong sorption of mercury to soils, it is unlikely that any

significant amount of the spilt mercury has entered or will enter the waterways in the future. Any

mercury, however, that enters the water may be transformed to methylmercury, as discussed in Section

1.2.2. Methylmercury is essentially a nervous system toxicant and is generally considered as the most

toxic form of mercury (USEPA 2001c). Because methylmercury effects different organs within the

human body, the possible risks from exposure are treated separately from exposure to other forms of

mercury (i.e., ionic and elemental). Note that potential impacts from methylmercury and other forms are

not considered to be additive.

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Benchmark Determination

The RA only addresses the oral ingestion of mercury. Inhalation exposure to the spilt mercury has been

assessed in earlier documents (Consulcont SAC 2000, SMI 2002).

Drinking Water Exposure

Table 3.1.1 lists some representative safe levels for mercury in drinking water. The lowest level of 1.0

ppb listed in Table 3.1.1 is utilized as the drinking water benchmark for humans. The Peruvian Ministry of

Health (Peru MH 1983) has issued a criterion value of 2.0 ppb for domestic water use.

Table 3.1.1 Representative Human Health Drinking Water Criteria

Country/Organization Mercury

(ppb) References

USA 2.0 USEPA (1997b) Peru 2.0 Peru MH (1983) European Union (EU) 1.0 EU (1992) Canada 1.0 Health Canada (1998) World Health Organization 1.0 WHO (1996)

Dietary-methylmercury

As discussed in Section 1.2.3, fish and seafood consumption typically accounts for the large majority of

mercury ingestion by humans. Additionally, mercury concentration in fish is almost all in the

methylmercury form and has greater absorption into humans than ionic or elemental forms (Richardson et

al. 1995). Humans essentially only consume methylmercury by eating fish or shellfish (WHO 1991). A

compilation of safe consumption levels for mercury in fish is shown in Table 3.1.2. No Peruvian

regulations for mercury concentrations in fish are available. The lowest value listed in Table 3.1.2 of 300

ppb (ww) is utilized as the benchmark for consumption of methylmercury in the RA. This value is for the

average dietary concentration of methylmercury, and not for any individual dietary item.

Dietary-elemental/ionic

In general, for oral ingestion, the USEPA approach for evaluating risk to humans utilizes a Reference

Dose, denoted RfD, to establish safe levels for chronic ingestion of a chemical. The USEPA defines a

RfD as “an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the

human population (including sensitive subgroups) that is likely to be without an appreciable risk of

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deleterious effects during a lifetime” (USEPA 1999b). However, the USEPA does not issue a RfD for

elemental mercury (USEPA 2001a).

Table 3.1.2 Listing of Values Reported as Safe Hg Limits by Various Countries and Regulatory Agencies for Fish

Country/Organization Type Hg (ppb, ww) References USA FDA- fish 1000 1 USA EPA- fish MeHg 300 2 Brazil Fish Std. 500 3 Canada Fish Std. 500 3 Denmark Fish Std. 500 3 Ecuador Fish Std. 1000 3 Finland Fish Std. 1000 3 France Seafood 500-700 3 Germany Fish Std. 1000 3 Greece Fish Std. 700 3 India Fish Std. 500 3 Italy Fish Std. 700 3 Japan Fish-MeHg 300 3 Japan Fish- Total Hg 400 3 Netherlands Seafood 1000 3 Philippines Fish- MeHg 500 3 Spain Fish Std. 500 3 Sweden Fish Std. 1000 3 Switzerland Fish Std. 500 3 Thailand Fish Std. 500 3 Venezuela Seafood 500 3 Zambia Fish Std. 300 3 Australia/ New Zealand Fish/seafood standard 500-1000 4 World Health Organization Non-predatory /predatory fish 500/1000 5

1 FDA (U.S. Food and Drug Administration). 1998. Action levels for poisonous or deleterious substances in human food and animal feed. March 1998.

2 USEPA (U.S. Environmental Protection Agency). 2001. Water Quality Criterion for the Protection of Human Health: Methylmercury. EPA-823-R-01-001.

3 Nauen, C. 1983. Compilation of Legal Limits for Hazardous Substances in Fish and Fishery Products. Food and Agriculture Organization of the United Nations, Rome.

4 ANZFA (Australia New Zealand Food Authority). 1987. Food Standards Code: Standards A11- Specifications for Identity and Purity of Food Additives, Processing Aids, Vitamins, Minerals and Other Added Nutrients (as amended and current as of December 2001)

5 CODEX. 1991. Guideline Level for Methylmercury in Fish. Food Safety Programme. Codex Commission on Food Additives and Contaminants. WHO, Geneva.

For the non-fish portion of the diet (i.e., non methylmercury), an RfD derived for mercuric sulfide by the

U.S. Department of Energy (DOE)- Oak Ridge National Laboratory (ORNL 2002) of 0.04 mg of Hg per

Kg of bodyweight per day (mg/kg-day) is used. Additional information on the derivation of this value is

included as Appendix A. Due to similar solubility (Table 1.2.1) and bioavailability between elemental

mercury and mercuric sulfide, ORNL states that this RfD value is also applicable to elemental mercury.

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As discussed with SENASA personnel in November 2000, the RfD of 0.04 mg/Kg-day can be used to

arrive at safe concentrations of mercury in non-fish food items. By multiplying the RfD by the average

bodyweight of a person, which in this case is assumed to be 60 Kg, the average safe daily intake of

mercury would be 2.4 mg of mercury per day (0.04 mg/Kg-day * 60 Kg). The USEPA (1997c) assumes

that an average person in the U.S. consumes 1.5 kg of food per day. Assuming the same food ingestion

for residents near the spill, 2.4 mg of mercury could be contained in 1.5 kg of food. The allowable

average concentration of mercury in non-fish food, therefore, is equal to 1600 ppb (2.4 mg Hg/ 1.5 Kg

food = 1.6 mg /kg or 1600 ppb). If only 1 Kg of food is consumed, the average safe level is equal to 2400

ppb. In general, the population living near the spill are smaller (height and weight) than the average person

in the USA, upon which the USEPA bases their calculations. It is therefore reasonable to assume that the

average diet for residents near the spill is less than the 1.5 Kg of food per day assumed by the USEPA

(1997c). However, to be conservative, the RA assumes a diet of 1.5 Kg per day, which results in an

average safe mercury concentration in the diet of 1600 ppb. It is important to note, however, that the 1600

ppb safe level is the average for all of the diet. Consumption of occasional individual food items exceeding

this value is not problematic, unless the overall average concentration of mercury in the diet exceeds 1600

ppb.

Summary

In summary, the benchmark values for humans are 1.0 ppb for drinking water, 300 ppb (ww) for

methylmercury consumption in fish and shellfish, and 1600 ppb (ww) for non-fish dietary consumption. All

of these values are based on regulatory guidance values.

3.2 Mercury Toxicity to Other Terrestrial Animals and Benchmark Determination 3.2.1 Birds and Mammals

Overall, the reported toxic symptoms of mercury poisoning in both animals and plants are non-specific.

Essentially, this means that the same symptoms could be explained by a wide variety of causes, and

cannot be easily associated with mercury exposure. Puls (1992) reviewed the literature on symptoms

reportedly associated with mercury toxicity in various domestic animals. The symptoms reported, and the

animals affected by the different symptoms are shown below:

n

ataxia (incoordination): cats, cattle, pigs n

muscle weakness: cats, pigs n

tremors: cats

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n changes in urine production/chemistry: cats, cattle, horses

n stomach irritation/damage: horses

n diarrhea: horses

n loss of appetite/weight: horses, pigs, poultry

n decreased fertility: poultry

These symptoms are similar to effects that are observed in animals afflicted with a variety of diseases, or

other conditions (e.g., poor nutrition or parasites).

The kidney is the primary concentrating organ for inorganic mercury in mammals and fish. For mammals,

the kidney typically contains 50-80% of all of the mercury in the body (WHO 1991). The level of the

glutathione enzyme, in the kidney, is the likely primary determinant of the ultimate concentration of

mercury in kidneys. Other known sites of mercury deposition in animals are fat reserves, brain, and liver.

In fish-eating birds, mercury builds up to a greater extent in the liver than in the kidney (Scheuhammer et

al. 1998). As with humans, methylmercury effects in animals are typically manifested in the central

nervous system, with effected animals become anorexic and lethargic (Amdur et al. 1991). Because

methylmercury targets different organ systems than other mercury forms, it is considered separately from

the other forms, and methylmercury effects are not considered to be additive to effects from other

mercury forms.

Overall, methylmercury is more mobile in the body than ionic (e.g., HgO and HgS) or elemental mercury

(Sweet and Zelikoff 2001). One example of this is that methylmercury crosses the placenta and can effect

fetuses of pregnant animals, whereas inorganic mercury is essentially unable to cross the placenta (Amdur

et al. 1991, WHO 1991). Up to 95% of ingested methylated forms of mercury are absorbed in the

gastrointestinal tract of mammals, whereas only 7-15% of ingested inorganic salt forms (e.g., mercuric

chloride, HgCl2) are absorbed, and approximately 0.01% of ingested elemental mercury is absorbed

(Amdur et al. 1991, WHO 1991). Excretion of inorganic mercury in mammals is through urine, bile, feces,

and sweat (Sweet and Zelikoff 2001). Birds also excrete mercury by molting feathers. Mercury is

incorporated into the disulfide bonds in the keratin protein of feathers, and is lost when the feathers are

molted by the birds (Eisler 2000).

Dietary and drinking water benchmarks

Table 3.2.1 lists NOAEL and Effect Levels of mercury in the diet of birds and mammals. NOAEL values

are listed first and are unshaded. The Effect Levels in Table 3.2.1 are shaded and listed from lowest to

highest effect concentrations. All of the dietary values are listed in dry weight unless noted otherwise. If

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the report did not state if the concentration was based on wet or dry weight, dry weight was assumed to

be conservative.

Table 3.2.1 NOAEL and Effect Levels of Dietary Mercury for Mammals and Birds

Species ppb,dw Chemical Form/Notes Effect Reference MAMMALS- NOAEL

Rat 500 Methyl Hg chloride- chronic NOAEL Sample et al. 1996 Rat 800 Total, 90 day physiology NOAEL Dellinger et al. 1995 Animal (general) 1000 Hg2+, growth effects NOAEL NAS 1980; Underwood 1977 Mink 1100 Methyl Hg chloride NOAEL Wobeser and Swift 1976 Animal (general) 2000 Total Hg Safe limit Hapke 1991a Mink (ww*) 7930 HgCl; chronic, reproduction NOAEL Aulerich et al. 1974 Mouse 69500 Mercuric sulfide-chronic NOAEL Sample et al. 1996

MAMMALS- EFFECT LEVELS American mink 1800 Methyl Hg chloride Lethal Wobeser and Swift 1976 Northern river otter

2000 Methyl Hg Lethal O’Connor and Nielsen 1981

Rat 2500 Methyl Hg chloride Reduced pup viability Sample et al. 1996 Mouse 8000 Hg(NO3)2 LD50 Von Burg and Greenwood 1991 Mouse 10000 Methyl Hg Impaired immune

response Von Burg and Greenwood 1991

Rat 15000 Methyl Hg chloride Renal tumors Mitsumori et al. 1984 Human 29000 HgCl2 LD10 Von Burg and Greenwood 1991 Rat 210000 HgCl LD50 Von Burg and Greenwood 1991 Human 357000 HgI2 LD10 Von Burg and Greenwood 1991 Mouse 388000 HgNO3 LD50 Von Burg and Greenwood 1991 Human 1429000 Elemental Hg LD10 Von Burg and Greenwood 1991

BIRDS- NOAEL Zebra finch 2500 Methyl, 77 day exposure LD0 Wolfe et al. 1998 Japanese quail 4000 HgCl2- chronic exposure No effect Sample et al. 1996 Japanese quail 32000 Inorganic LD0 Eisler 2000

BIRDS- EFFECT LEVELS Mallard 500 MeHg dicyandiamide Decreased reproduction Heinz 1974 Mallard 3000 Methylmercury Decreased reproduction Eisler 2000 Zebra finch 5000 Methyl, 77 day exposure LD25 Wolfe et al. 1998 Poultry 5000 Total Hg Decreased reproduction Hapke 1987 Japanese quail 8000 HgCl2 LOAEL- chronic Sample et al. 1996 Japanese quail 8000 Methyl Hg Poisoning occurs Aagdal et al. 1978 Japanese quail 18000 Methyl Hg chloride Acute LD50 WHO 1989 Japanese quail 32000 HgCl2 No effect on growth rate;

decrea decreased fertilization WHO 1989

Japanese quail 42000 HgCl2 Acute LD50 WHO 1989 Japanese quail 47000 Methyl Hg chloride 5-day LC50 WHO 1989 Pheasant 3790000 HgCl2 5-day LC50 WHO 1989 Mallard 5000000 HgCl2 5-day LC50 WHO 1989 Japanese quail 5086000 HgCl2 5-day LC50 WHO 1989

Unshaded cells are NOAELs and shaded cells are Effect Levels *ww= wet weight diet

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Methylmercury is reported to be lethal to mink and otters at a dietary concentration of 1800 ppb and 2000

ppb, respectively (Table 3.2.1). Both of these mammals are members of the Carnivore family and are

primarily fish-eaters. Rodents are less sensitive, with non-lethal effects reported for rats at a dietary

methylmercury concentration of 2500 ppb (Table 3.2.1). Reported lethal concentrations of ionic forms of

mercury range from an LD50 (lethal dose for 50% of the test population) of 8000 ppb for mice exposed to

Hg(NO3)2 to an LD50 of 388,000 ppb for mice exposed to HgNO3.

Reported dietary NOAELs for methylmercury are 500 ppb for rats and 1100 ppb for mink. NOAELs for

ionic mercury forms range from 1000 ppb for animals in general up to 69,500 ppb for mice (Table 3.2.1).

The most relevant NOAEL for elemental mercury exposure is the value of 69,500 ppb value for mice

exposed to chronic levels of mercuric sulfide (HgS). Mercuric sulfide is similar to elemental mercury in

terms of having a low solubility (Table 1.2.1) and bioavailability (ORNL 2002). However, to be

conservative, the general animal NOAEL of 2000 ppb (dw) from Hapke (1991a) is set as the dietary

benchmark value for most mammals in this risk assessment. As a comparison to this value, the U.S.

Department of Energy (DOE; Sample et al. 1996) has issued benchmark values for mercuric sulfide and

mercuric chloride. All of the benchmark values for the exposure of different species to mercuric sulfide

exceed 26,000 ppb (ww). The benchmark values for mercuric chloride range from 3400 ppb (ww) for

bats to 11840 ppb (ww) for deer.

An additional benchmark value of 1100 ppb (dw) is set for mammals that essentially only consume fish.

This second value is equal to the NOAEL reported for mink, which is the species that had the lowest

reported toxic concentration of 1800 ppb (Table 3.2.1). There are, however, no known species of fish-

eating (piscivorous) mammals that occur in the area (Table 2.3.1).

The lowest reported Effect Level of 500 ppb (reproduction in mallard ducks) is for methylmercury

dicyandiamide. This form of methylmercury was developed as a pesticide, and is therefore less relevant

to understanding the toxicity of naturally-occurring chemical forms of mercury. The next lowest Effect

Level is 3000 ppb methylmercury for mallards. Other reported Effect Levels (Table 3.2.1) are an LD25

of 5000 ppb for zebra finches (methylmercury), decreased reproduction in poultry at 5000 ppb (total

mercury), and a chronic LOAEL for Japanese quail of 8000 ppb (HgCl2). As shown in Table 1.2.1,

mercuric chloride is a much more soluble ionic form of mercury than either the mercuric oxide or mercuric

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sulfide forms that naturally occur in the environment. Based on the values listed in Table 3.2.1, the

concentrations of methylmercury and mercuric chloride that are toxic to birds are similar.

Reported dry weight NOAELs are 2500 ppb methylmercury for zebra finches, 4000 ppb mercuric chloride

and 32,000 ppb inorganic mercury for Japanese quail (Table 3.2.1). Based on these NOAEL values, a

benchmark concentration of 4000 ppb (dw) is selected to be protective of birds from ionic mercury

exposure. This value is equal to the lower of the two NOAEL values listed for Japanese quail. For

piscivorous birds, a second safe dietary benchmark is set at 2500 ppb (dw) based on the NOAEL for

methylmercury exposure of zebra finches.

Both mammals and birds are relatively insensitive to mercury exposure from drinking water (Table 3.2.2).

The lowest reported toxic values are 5000 ppb for mammals and 250,000 ppb for birds. However, to be

conservative, the benchmark value for human drinking water of 1 ppb mercury is utilized as the

benchmark for all animals.

Table 3.2.2 NOAEL and Effect Levels of Mercury in Drinking Water for Mammals and Birds

Species ppb Chemical Form/Notes Effect Reference MAMMALS- NOAEL

Mouse 1000 Methylmercury No effect Schroeder and Michener 1975 Mouse 5000 HgCl2 No effect Schroeder and Michener 1975

MAMMALS- EFFECT LEVELS Mouse 5000 Methylmercury Decreased growth Schroeder and Michener 1975

BIRDS- NOAEL Chicken 300000 HgCl2 in drinking water; chicks No effect WHO 1989

BIRDS- EFFECT LEVELS Chicken 250000 HgCl2 in drinking water; 8-

month old hens Slight decrease in body weight, smaller eggs

WHO 1989

Chicken 300000 HgCl2 in drinking water; juveniles

Decreased growth WHO 1989

Chicken 500000 HgCl2 in drinking water; 4-week males

Decreased growth rate, higher mortality

WHO 1989

Unshaded cells are NOAELs and shaded cells are Effect Levels

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Tissue benchmarks

In addition to NOAELs and Effect Levels of mercury in animal diets, the scientific literature was

reviewed to determine NOAELs and Effect Levels of mercury in the tissues of animals. Literature values

for tissue concentrations are shown in Table 3.2.3. As before, NOAELs are listed first, followed by

shaded Effect Levels.

Table 3.2.3 Reported NOAEL and Effects Levels of Mercury in Animal Tissue

Species ppb, dw Notes Tissue Type Effect Reference MAMMAL- NOAEL

Pig 100 Total Hg Liver No effect Hapke 1991a Rat 120 Total Hg Heart No effect Kostic et al. 1977 Rat 780 Total Hg Kidney No effect Kostic et al. 1977 Rat 800 Total Hg Liver No effect Kostic et al. 1977 Rodents 900 Total Hg Liver Normal Fimreite et al. 1970 Rabbit 1200 Total Hg Muscle Normal tissue concentration Falandysz et al. 1994 Rat 1260 Total Hg Lung No effect Kostic et al. 1977 Sheep 3700 Total Hg Muscle Normal tissue concentration Falandysz et al. 1994

MAMMAL- EFFECT LEVELS American mink 76000 Total Hg Muscle Lethal Wobeser and Swift 1976 Northern river otter 80000 Total Hg Muscle Lethal (chronic) O’Connor and Nielson

1981 American mink 160000 Total Hg Kidney Lethal Wobeser and Swift 1976 Northern river otter 165000 Total Hg Liver Lethal (chronic) O’Connor and Nielson

1981 Northern river otter 195000 Total Hg Kidney Lethal (chronic) O’Connor and Nielson

1981 American mink 291000 Total Hg Liver Lethal Wobeser and Swift 1976

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Table 3.2.3 Reported NOAEL and Effects Levels of Mercury in Animal Tissue (continued)

BIRD- NOAEL Poultry 40 Total Hg General tissue Normal background Hapke 1991b Songbirds 150 Total Hg Liver Normal background Fimreite et al. 1970 Upland game birds 1750 Total Hg Liver Normal background Fimreite et al. 1970 Chicken 1800 Total Hg Muscle Normal tissue concentration Falandysz et al. 1994 Common tern 3930 Total Hg Liver No effect Wolfe et al. 1998 Duck/geese sp. 4300 Total Hg Muscle Normal tissue concentration Falandysz et al. 1994 Duck/geese sp. 5000 Total Hg Muscle Normal tissue concentration Falandysz et al. 1994 Turkey 6000 Total Hg Muscle Normal tissue concentration Falandysz et al. 1994 Common tern 33600 Total Hg Liver Nesting success Wolfe et al. 1998 Common tern 76700 Total Hg Liver Hatching success Wolfe et al. 1998

BIRD- EFFECT LEVELS Common loon 7400 Total Hg Brain Reduced reproduction Wolfe et al. 1998 Chicken 15000 Total Hg Hen liver Decreased hatchability Fimreite 1970 Pheasant 15000 Total Hg Liver Decreased hatchability Borg et al. 1969 Water birds 18500 Total Hg Liver Toxic threshold- reproduction Zillioux et al. 1993 Am. Black Duck 18500 Total Hg Brain Failure to hatch Wolfe et al. 1998 Great white heron 22200 Total Hg Liver Correlated mortality from chronic disease Wolfe et al. 1998 Great white heron 26700 Total Hg Liver Increased disease and emaciation Wolfe et al. 1998 Common loon 30900 Total Hg Liver Decreased hatchability Wolfe et al. 1998 Zebra finch 74100 Total Hg Brain 25% mortality Scheuhammer 1988 Common tern 82200 Total Hg Liver Abnormal feather loss in juveniles Wolfe et al. 1998 Common tern 102000 Total Hg Liver Decreased fledge success Wolfe et al. 1998 Common loon 110000 Total Hg Liver Reduced nesting success Wolfe et al. 1998 Birds-general 111000 Total Hg Liver Neurological effects Heinz 1974 Osprey 130000 Total Hg Liver lethal Wolfe et al. 1998 Japanese quail 135000 Methyl Hg Liver Poisoning occurs Aagdal et al. 1978 Common grackle 150000 Total Hg Kidney LD33 Wolfe et al. 1998 Common loon 192000 Total Hg Liver Reduced hatching success Wolfe et al. 1998 Common grackle 202000 Total Hg Liver LD33 Wolfe et al. 1998 Red-winged blackbird 275000 Total Hg Kidney LD33 Wolfe et al. 1998 European starling 320000 Total Hg Kidney LD33 Wolfe et al. 1998 Gannet 362000 Total Hg Liver Lethality Wolfe et al. 1998 European starling 384000 Total Hg Liver LD33 Wolfe et al. 1998 Red-winged blackbird 469000 Total Hg Liver LD33 Wolfe et al. 1998

TERRESTRIAL INVERTEB RATE- NOAEL

Earthworm 2 Methyl Hg Whole Normal Vonburg and Greenwood 1991 Earthworm 20 Total Hg Whole Normal Vonburg and Greenwood 1991 Earthworm(ww) 27000 Total Hg Whole NOAEL-reproduction Beyer et al. 1985

TERRESTRIAL INVERTEB RATE- EFFECT LEVELS

Aphid 25000 Methyl Hg Whole LD50 Haney and Lipsey 1973 Green lacewing 31000 Methyl Hg Whole Lethal Haney and Lipsey 1973 Earthworm (ww) 85000 Total Hg Whole 70% decrease in reproduction Beyer et al. 1985

Unshaded cells are NOAELs and shaded cells are Effect Levels * unless noted otherwise, values are for dry weight tissues; ww= wet weight tissue concentration

The highest NOAEL level for mammals in Table 2.3.2 is 3700 ppb (dw) in sheep muscle. Assuming 80%

moisture in muscle, this is equivalent to 740 ppb on a wet weight basis. Higher NOAELs, up to 76700 ppb

(dw) are listed for birds. The lowest Effect Level for birds is 7400 ppb (dw) in loon brain tissue. The

highest muscle NOAEL for birds is 6000 ppb (dw) for turkeys. Again, assuming 80% moisture, this is

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equivalent to 1200 ppb on a wet weight basis. The 740 ppb (ww) value from sheep muscle and the 1200

ppb (ww) value for turkey muscle are utilized as the benchmark tissue concentrations in the RA.

NOAEL concentrations of mercury in terrestrial invertebrate tissue range from 2 ppb (dw) to 27,000 ppb

(ww). Reported Effect Levels are equal to or higher than 25000 ppb (dw). The lowest Effect Level of

25000 ppb (dw) was divided by an uncertainty factor (UF) of 50, as recommended by Calabrese and

Baldwin (1993), to go from a lethal endpoint to a chronic NOAEL. The resulting benchmark value is 500

ppb (dw). Assuming 80% moisture, the corresponding wet weight benchmark value is 150 ppb.

3.2.2 Plants

The World Health Organization (WHO 1989, 1991) states that plants are generally insensitive to the

inorganic forms of mercury (i.e., elemental and ionic), likely because of the strong sorption of mercury to

soil particles, which largely prevents plant uptake and toxicity. Evidence of the lack of mercury uptake by

plants comes from greenhouse studies, as well as reports from sites with plants growing on mine spoils or

near mercury smelters (Lindberg et al. 1979). Patra and Sharma (2000), in a review of mercury toxicity to

plants, also state that mercury availability to plants is low, and that large increases in soil mercury

concentrations do not result in large increases in mercury uptake into plant tissues. Organic forms of

mercury (i.e., methylmercury) are more available to plants than inorganic forms, though methylmercury is

uncommon in soils since the reducing conditions required to methylate mercury rarely occur in soils (Davis

et al. 1997).


NOAEL and Effect Levels of mercury in plant tissues are listed in Table 3.2.4. Mercury concentrations

in vegetables, or other herbaceous plants, need to exceed 4600 ppb (dw) before there is a possibility of

mercury toxicity. The most sensitive grasses are affected by tissue concentrations as low as 3333 ppb in

grain, 4000 ppb in stems, and 59,000 ppb in roots (dw; Table 3.2.4). NOAEL values for tree and shrub

tissue are as high as 3500 ppb (dw). No toxic levels for trees and shrubs were located in the literature.

Based on the review of the literature, plant toxicity would likely be manifested by a reduction in the rate of

growth, not the overall survival or viability of plants (i.e., mercury will not kill the plant). A benchmark

value of 3000 ppb (dw) for plant tissue is established for plant tissue in the RA. This value was chosen

since it is within the reported NOAEL levels and is less than the lowest Effect Concentration of 3333 ppb

(dw) for plants.

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Table 3.2.4 NOAEL and Effect Levels of Mercury in Plant Tissue

Species ppb (dw) Hg form Tissue Type Effect Reference GRASS- NOAEL

Corn (maize) 3 Total Hg Grain NOAEL Kabata-Pendias and Pendias 1992 Corn (maize) 4.6 Total Hg Grain NOAEL Shacklette 1980 Rye 9 Total Hg Grain NOAEL Fergusson 1990 Oats 9 Total Hg Grain NOAEL Gracey and Stewart 1974 Oats 9 Total Hg Grain Normal Fergusson 1990 Wheat 11 Total Hg Grain NOAEL Gracey and Stewart 1974 Wheat 12 Total Hg Grain Normal Saha et al. 1970 Oats 12 Total Hg Grain Normal Kabata-Pendias and Pendias 1992 Barley 12 Total Hg Grain Normal Fergusson 1990 Barley 12 Total Hg Grain NOAEL Gracey and Stewart 1974 Barley 12 Total Hg Grain Normal Saha et al. 1970 Oats 14 Total Hg Grain Normal Fergusson 1990 Wheat 14 Total Hg Grain Normal Kabata-Pendias and Pendias1992 Rice 15 Total Hg Grain NOAEL VonBurg and Greenwood 1991 Barley 19 Total Hg Grain Normal Kabata-Pendias and Pendias1992 Oats 33 Total Hg Straw NOAEL Gracey and Stewart 1974 Wheat 36 Total Hg Straw NOAEL Gracey and Stewart 1974 Grass (mixed) 70 Total Hg Leaf NOAEL-growth Cocking et al. 1995 Barley 80 Total Hg Straw NOAEL Gracey and Stewart 1974 Sheep fescue 300 Total Hg Shoot NOAEL-growth Cocking et al. 1995 Rice 500 Total Hg Stem Critical level* Adriano 1986 Kentucky bluegrass 750 Total Hg Shoot NOAEL-growth Cocking et al. 1995 Bermuda grass 1000 Total Hg Stems NOAEL growth Weaver et al. 1984 Velvet bentgrass 1680 Total Hg Shoot NOAEL-growth Estes et al. 1973 Barley 2000 MeHg

hydroxide Leaves Upper critical

level Lipsey 1975

Grass (mixed) 2200 Total Hg Root NOAEL-growth Cocking et al. 1995 Kentucky bluegrass 2500 Total Hg Root NOAEL-growth Cocking et al. 1995 Bermuda grass 2900 Total Hg Leaves NOAEL growth Weaver et al. 1984 Sheep fescue 3250 Total Hg Root NOAEL-growth Cocking et al. 1995 Barley 3000 Hg2+ Leaves Upper critical Davis et al. 1978 Rice 1000000 Total Hg Roots Critical level Adriano 1986

GRASS- EFFECT LEVELS Corn (maize) 3333 Total Hg Grain Decreased growth Lipsey 1975 Oats 4000 Total Hg Straw Decreased growth Sorteburg 1978 Bermuda grass 59000 Total Hg Roots Decreased growth Weaver et al. 1984

VEGETABLES - NOAEL Jewel flower 1.4 Total Hg Whole plant NOAEL Leonard et al. 1998 Tall whitetop 1.5 Total Hg Whole plant NOAEL Leonard et al. 1998 Beans 3 Total Hg Pods NOAEL Kabata-Pendias and Pendias1992 Woodland strawberry 3.7 Total Hg Whole plant NOAEL Leonard et al. 1998 Carrot 5.7 Total Hg Roots NOAEL Shacklette 1980 Cabbage/broccoli 6.5 Total Hg Leaves NOAEL Kabata-Pendias and Pendias1992 Lettuce 8.3 Total Hg Leaves NOAEL Shacklette 1980 Beans 11 Total Hg Pods NOAEL Kabata-Pendias and Pendias1992 Flax 19 Total Hg Straw NOAEL Gracey and Stewart 1974 Oilseed rape 24 Total Hg Straw NOAEL Gracey and Stewart 1974 Alfalfa (lucerne) 39 Total Hg Foliage NOAEL Gracey and Stewart 1974 Oilseed rape 40 Total Hg Tubers NOAEL Gracey and Stewart 1974 Oilseed rape 51 Total Hg Tops NOAEL Gracey and Stewart 1974 Lima bean 58 Total Hg Bean Normal

background Haller et al. 1968

FINAL


Table 3.2.4 NOAEL and Effects Concentrations of Mercury in Plant Tissue (continued)

Species Tissue

ppb (dw) Mercury

Form Tissue Type Effect Reference

VEGETABLES - NOAEL (cont.) Broadleaved pepperweed 70 Total Hg Stem NOAEL- growth Leonard et al. 1998 Carrot 86 Total Hg Roots NOAEL Kabata-Pendias and Pendias1992 Pea 128 Total Hg Pea Normal background Haller et al. 1968 Cabbage/broccoli 166 Total Hg Aboveground Normal background Bowen 1974 Douglas' sagewort 200 Total Hg Stem NOAEL- growth Leonard et al. 1998 Douglas' sagewort 200 Total Hg Leaves NOAEL- growth Leonard et al. 1998 Woodland strawberry 300 Total Hg Stem NOAEL- growth Leonard et al. 1998 Broadleaved pepperweed 300 Total Hg Leaves NOAEL- growth Leonard et al. 1998 Common milkweed 350 Total Hg Root NOAEL- growth Cocking et al. 1995 Common milkweed 470 Total Hg Leaf NOAEL- growth Cocking et al. 1995 Jewel flower 500 Total Hg Root NOAEL- growth Leonard et al. 1998 Jewel flower 800 Total Hg Stem NOAEL- growth Leonard et al. 1998 Broadleaved pepperweed 1200 Total Hg Root NOAEL- growth Leonard et al. 1998 Jewel flower 1390 Total Hg Whole plant NOAEL- growth Leonard et al. 1998 Broadleaved pepperweed 1500 Total Hg Whole NOAEL- growth Leonard et al. 1998 Woodland strawberry 3300 Total Hg Root NOAEL- growth Leonard et al. 1998 Woodland strawberry 3700 Total Hg Whole NOAEL- growth Leonard et al. 1998 Douglas' sagewort 4200 Total Hg Root NOAEL- growth Leonard et al. 1998 Douglas' sagewort 4600 Total Hg Whole plant NOAEL- growth Leonard et al. 1998

VEGETABLES - EFFECT LEVELS

Cabbage/broccoli 6000 Hg +1 Outer leaves Decreased growth Hara and Sonoda 1979 Cabbage/broccoli 8000 Hg +2 Outer leaves Decreased growt h Hara and Sonoda 1979

TREE/SHRUB- NOAEL Composite 1 0.08 Total Hg Shoot NOAEL Gnamus et al. 2000 Poplar 0.1 Methylated Leaves NOAEL May et al. 1985 Composite 1 0.21 Total Hg Shoot NOAEL Gnamus et al. 2000 Spruce 0.5 MeHg Needles NOAEL May et al. 1985 Composite 1 0.58 Total Hg Shoot NOAEL Gnamus et al. 2000 Eucalyptus 3.2 Total Hg Whole plant NOAEL- growth Leonard et al. 1998 Douglas sage 4.6 Total Hg Whole plant NOAEL- growth Leonard et al. 1998 Composite 1 14.4 Total Hg Shoot NOAEL Gnamus et al. 2000 Poplar 20 Total Hg Leaves NOAEL May et al. 1985 Composite 1 51.8 Total Hg Shoot NOAEL Gnamus et al. 2000 Spruce 70 Total Hg Needles NOAEL May et al. 1985 Tasmanian bluegum 80 Total Hg Leaves NOAEL –growth Leonard et al. 1998 Tasmanian bluegum 100 Total Hg Stem NOAEL- growth Leonard et al. 1998 Tasmanian bluegum 2900 Total Hg Root NOAEL Leonard et al. 1998 Tasmanian bluegum 3200 Total Hg Whole plant NOAEL- growth Leonard et al. 1998 Tea 3500 Total Hg Stems NOAEL- growth Shacklette 1970


1 Composite of 42 plant species MeHg= methylmercury * The critical value is the upper limit of mercury in tissue for which no effects to the plant are observed.

NOAEL and Effect Levels of mercury in soil are listed in Table 3.2.5. The lowest concentration of

mercury in soil that resulted in an effect (decreased growth) is 25000 ppb (dw). Reported effects tend to

be related to plant growth, rather than germination or survival. As an example, Panda et al. (1992) did not

find significant effects on barley germination at soil mercury concentrations up to 103,000 ppb, whereas

FINAL


growth of the seedlings was decreased at mercury soil concentrations of 64,000 ppb or greater. A

benchmark concentration of 10,000 ppb (dw) is selected on the basis that it is within the reported range of

NOAEL values, and is only 40% of the lowest Effect Level. This value is also equal to the lowest Soil

Screening Level for mercury listed by the USEPA (2001e). This value, however, is driven by human

health concerns, rather than ecological effects.

Table 3.2.5 NOAEL and Effect Levels of Mercury in Soil to Plants

Species ppb (dw) Comment Effect Reference GRASS-SOIL NOAEL

Grass 11000-31000 Total Hg NOAEL Cocking et al. 1995 Bermuda grass 20000-62000 Total Hg -Clay soil NOAEL Weaver et al. 1984 Bermuda grass 23000-40000 Total Hg -Sandy soil NOAEL Weaver et al. 1984 Barley 34900 Total Hg No effect on growth Panda et al. 1992 Bermuda grass 40000 Total Hg- Sandy loam soil NOAEL Weaver et al. 1984 Sheep fescue 50000-70000 Total Hg NOAEL Cocking et al. 1995 Kentucky bluegrass 50000-70000 Total Hg NOAEL Cocking et al. 1995 Velvet bentgrass 450000 Total Hg No effect Estes et al. 1973

GRASS- EFFECT LEVELS

Bermuda grass 25000-67000 Total Hg -Loamy soil Decreased growth Weaver et al. 1984 Bermuda grass 50000 HgCl2 Reduced growth Weaver et al. 1984 Barley 64000 Total Hg 19% growth inhibition-

height Panda et al. 1992

Bermuda grass 65000 Total Hg -Sandy soil Decreased growth Weaver et al. 1984 Barley 103300 Total Hg 44% growth inhibition-

height Panda et al. 1992

VEGETABLE(FORB)- NOAEL

Flax 23 Total Hg; Avg. of ~2000 soil samples

Normal Gracey and Stewart 1974

Common milkweed 11000-31000 Total Hg NOAEL Cocking et al. 1995 Jewel flower 23800 Total Hg NOAEL Leonard et al. 1998 Broadleaved pepperweed 31800 Total Hg NOAEL Leonard et al. 1998 Woodland strawberry 33700 Total Hg NOAEL Leonard et al. 1998 Douglas’ sagewort 53500 Total Hg NOAEL Leonard et al. 1998 Garden onion 100000 Total Hg No effect on emergence Adriano 1986

VEGETABLE(FORB)- EFFECT LEVELS

Lettuce/carrot 50000 Total Hg Severe loss of biomass Adriano 1986

TREE- NOAEL

Composite woody plants1 651 Methyl Hg NOAEL Gnamus et al. 2000 Tasmanian bluegum 25800 Total Hg NOAEL Leonard et al. 1998 Composite woody plants1 2456000 Total Hg NOAEL Gnamus et al. 2000

Unshaded cells are NOAELs and shaded cells are Effect Levels 1 Composite of 42 plant species

FINAL


3.3 Mercury Toxicity to Aquatic Biota and Benchmark Determination

Several factors influence the toxicity of mercury to aquatic biota, including the form of mercury,

developmental stage of exposed organisms, and the chemistry of the water. Changes in the temperature,

salinity, and hardness of the water can alter the toxicity of mercury to biota (WHO 1989). Generally,

organic forms are more toxic to aquatic biota than inorganic forms of mercury. Early (larval) lifestages are

typically more sensitive to impacts than are adults. Sublethal effects include physiological and biochemical

alterations, as well as impacts to reproductive abilities (WHO 1991).


NOAEL and Effect Levels of mercury in water to aquatic biota are listed in Table 3.3.1. Effects are

broken-out separately for fish and aquatic macroinvertebrates. NOAELs are listed first from lowest to

highest, followed by Effect Levels (shaded) from lowest to highest concentrations. There are relatively

few NOAELs in comparison to reported Effect Levels. The lowest reported toxic value for fish is 3.7 ppb

methylmercuric chloride for fingerling rainbow trout (Table 3.3.1). The lowest reported toxic value for

aquatic macroinvertebrates is an LD50 of 2 ppb inorganic mercury for crayfish. The highest reported

NOAELs are 0.29 ppb for fish and 30 ppb for macroinvertebrates. USEPA (1999c) regulations for

protection of aquatic life are 1.4 ppb for acute exposures (i.e., short-term) and 0.77 ppb for chronic, or

continual, exposures (USEPA 1999c). The Peruvian Ministry of Health lists a value of 0.2 ppb for

protection of aquatic life (Peru MH 1983). The 0.2 ppb criterion value is used as the benchmark value for

water exposure for all aquatic biota.

FINAL


Table 3.3.1 NOAEL and Effect Levels of Mercury in Water to Aquatic Biota

Species ppb Notes Effect Reference FRESHWATER FISH- NOAEL

Pike 0.036 Methyl Hg Not poisoned Lockhart et al. 1972 Brook trout - larvae 0.29 Mercuric chloride NOEC McKim et al. 1976

FRESHWATER FISH- EFFECTS LEVELS Rainbow trout-fingerlings 3.7 Methylmercuric chloride Toxic - 70d Matida et al. 1971 Mosquitofish 10 Hg +2 Impaired escape

behavior Kania and O’Hara 1974

Rainbow trout-fingerlings 24 Organic Hg 96-hr LC50 Wobeser 1975 Guppy 30 Hg+2 Acute toxicity USEPA 1986 Rainbow trout, Steelhead 33 Mercurous nitrate (Hg+1) 96-hr LC50 Hale 1977 Rainbow trout, Steelhead 42 Organic Hg 96-hr LC50 Wobeser 1975 Colorado pikeminnow-larva 57 Hg+2 96-hr LC50 Buhl 1997 Bonytail-larva 61 Hg+2 96-hr LC50 Buhl 1997 Brook trout 65 Organic 96-hr LC50 USEPA 1980 Catfish 75 Inorganic 96-hr LC50 WHO 1989 Brook trout 75 Organic 96-hr LC50 McKim et al. 1976 Striped bass 90 Inorganic 96-hr LC50 Rehwoldt et al. 1972 Razorback sucker-juvenile 90 Hg+2 96-hr LC50 Buhl 1997 Bonytail-juvenile 108 Hg+2 96-hr LC50 Buhl 1997 Banded killifish 110 Inorganic 96-hr LC50 Rehwoldt et al. 1972 Razorback sucker-larva 128 Hg+2 96-hr LC50 Buhl 1997 Catfish 131 Inorganic 240-hr LC50 WHO 1989 American eel 140 Inorganic 96-hr LC50 Rehwoldt et al. 1972 Striped bass 140 Inorganic 48-hr LC50 Rehwoldt et al. 1972 Largemouth bass 140 Mercuric chloride LC50 - 8d Birge et al. 1978 Banded killifish 160 Inorganic 48-hr LC50 Rehwoldt et al. 1972 Colorado pikeminnow-juvenile

168 Hg+2 96-hr LC50 Buhl 1997

Fathead minnow- 30 day olds 168 Inorganic 96-hr LC50 Snarsky and Olson 1982 Fathead minnow- 30 day olds 172 Inorganic 96-hr LC50 Spehar and Fiandt 1986 Common Carp 180 Inorganic 96-hr LC50 Rehwoldt et al. 1972 American eel 190 Inorganic 48-hr LC50 Rehwoldt et al. 1972 Common Carp 210 Inorganic 48-hr LC50 Rehwoldt et al. 1972 White perch 220 Inorganic 96-hr LC50 Rehwoldt et al. 1972

FINAL


Table 3.3.1 NOAEL and Effect Levels of Mercury in Water to Aquatic Biota (continued)

Species ppb Notes Effect Reference

FRESHWATER FISH- EFFECTS LEVELS (cont.)

Striped bass 220 Inorganic 24-hr LC50 Rehwoldt et al. 1972 Rainbow trout 220 Inorganic 96-hr LC50 WHO 1989 American eel 250 Inorganic 24-hr LC50 Rehwoldt et al. 1972 Banded killifish 270 Inorganic 24-hr LC50 Rehwoldt et al. 1972 Rainbow trout 280 Inorganic 96-hr LC50 WHO 1989 Rainbow trout 300 Inorganic 48-hr LC50 WHO 1989 Pumpkinseed 300 Inorganic 96-hr LC50 Rehwoldt et al. 1972 Catfish 314 Inorganic 96-hr LC50 WHO 1989 Common Carp 330 Inorganic 24-hr LC50 Rehwoldt et al. 1972 White perch 340 Inorganic 48-hr LC50 Rehwoldt et al. 1972 Catfish 350 Inorganic 96-hr LC50 WHO 1989 Pumpkinseed 390 Inorganic 48-hr LC50 Rehwoldt et al. 1972 Rainbow trout 400 Inorganic 96-hr LC50 WHO 1989 Pumpkinseed 410 Inorganic 24-hr LC50 Rehwoldt et al. 1972 White perch 420 Inorganic 24-hr LC50 Rehwoldt et al. 1972 Salmonids (trout) 420 Inorganic 96-hr LC50 USEPA 1985 Rainbow trout 450 Inorganic 48-hr LC50 WHO 1989 White sucker 687 Mercuric chloride 96-hr LC50 Duncan and Klaverkamp 1983 African mouthbrooders 739 Inorganic 72-hr LC50 WHO 1989 Catfish 860 Inorganic 24-hr LC50 WHO 1989 Rainbow trout 903 Inorganic 24-hr LC50 Wobeser 1975 Brook trout- larva 930 Mercuric chloride Death - chronic McKim et al. 1976 African mouthbrooders 1000 Inorganic 48-hr LC50 WHO 1989 Freshwater tilapia 1000 Hg+2 Acute toxicity US EPA 1986 Catfish 1000 Inorganic 72-hr LC50 WHO 1989 African mouthbrooders 1256 Inorganic 24-hr LC50 WHO 1989 Catfish 1500 Inorganic 48-hr LC50 WHO 1989 Catfish 1700 Inorganic 24-hr LC50 WHO 1989 Flounder 3300 Inorganic 48-hr LC50 WHO 1989

FRESHWATER INVERTEBRATES- NOAEL

Daphnia magna 0.0001 Hg+2 Normal Lithner 1989 Daphnia magna 1.1 Hg+2 Chronic safe level USEPA 1986 Daphnia magna 30 Total Hg Toxic threshold Bringman and Kuhn 1959

FRESHWATER INVERTEBRATES- EFFECTS LEVELS

Crayfish 2 Inorganic 30-day LC50 WHO 1989 Daphnia magna 2.2 Hg+2 LC50 WHO 1989 Daphnia pulex 3 Inorganic 48-hr LC50 WHO 1989 Water flea 3.2 Inorganic 48-hr LC50 WHO 1989 Daphnia magna 3.4 Hg+2- 3 weeks 16% decrease in

reproduction Biesinger and Christensen 1972

Daphnia magna 5 Hg+2 LC50 USEPA 1985 Daphnia magna 5 Inorganic 48-hr LC50 Biesinger and Christensen 1972 Crayfish 7 Inorganic 96-hr LC50 Wren et al. 1995 Daphnia magna 13 Inorganic 21-day LC50 Biesinger and Christensen 1972 Midge 20 Inorganic 96-hr LC50 Rehwoldt et al. 1973 Crayfish 20 Inorganic 96-hr LC50 WHO 1989 Midge 60 Inorganic 24-hr LC50 Rehwoldt et al. 1973 Snail-adult 80 Inorganic 96-hr LC50 Rehwoldt et al. 1973 Midge- larvae 100 Inorganic 96-hr LC50 WHO 1989 Snail 135 Inorganic 96-hr LC50 WHO 1989 Snail 188 Inorganic 48-hr LC50 WHO 1989 Snail 296 Inorganic 72-hr LC50 WHO 1989 Midge- larvae 316 Inorganic 48-hr LC50 WHO 1989 Snail 369 Inorganic 48-hr LC50 WHO 1989

FINAL


Table 3.3.1 NOAEL and Effect Levels of Mercury in Water to Aquatic Biota (continued)

Species ppb Notes Effect Reference FRESHWATER INVERTEBRATES- EFFECTS LEVELS (cont.)

Crab 443 Inorganic 72-hr LC50 WHO 1989 Midge- larvae 547 Inorganic 96-hr LC50 WHO 1989 Crab 591 Inorganic 48-hr LC50 WHO 1989 Crab 739 Inorganic 24-hr LC50 WHO 1989 Midge- larvae 750 Inorganic 48-hr LC50 WHO 1989 Copepod 850 Inorganic 48-hr LC50 WHO 1989 Nais sp. 1000 Inorganic 96-hr LC50 Rehwoldt et al. 1973 Midge- larvae 1028 Inorganic 24-hr LC50 WHO 1989 Snail-adult 1100 Inorganic 24-hr LC50 Rehwoldt et al. 1973 Snail 1108 Inorganic 24-hr LC50 WHO 1989 Caddisfly 1200 Inorganic 96-hr LC50 Rehwoldt et al. 1973 Damselfly 1200 Inorganic 96-hr LC50 Rehwoldt et al. 1973 Nais sp. 1900 Inorganic 24-hr LC50 Rehwoldt et al. 1973 Mayfly 2000 Total Hg 96hr LC50 Warnick and Bell 1969 Stonefly 2000 Total Hg 96hr LC50 Warnick and Bell 1969 Caddisfly 2000 Inorganic 96-hr LC50 Warnick and Bell 1969 Snail-egg/embryo 2100 Inorganic 96-hr LC50 Rehwoldt et al. 1973 Copepod 2200 Inorganic 48-hr LC50 WHO 1989 Damselfly 3200 Inorganic 24-hr LC50 Rehwoldt et al. 1973 Daphnia magna 3610 Inorganic 48-hr LC50 WHO 1989 Mussels 3690 Inorganic LC50 - 96hr Wren et al. 1995 Daphnia magna 4300 Inorganic 48-hr LC50 WHO 1989 Daphnia magna 4890 Inorganic 24-hr LC50 WHO 1989 Caddisfly 5600 Inorganic 24-hr LC50 Rehwoldt et al. 1973 Mussels 5910 Inorganic 48-hr LC50 WHO 1989 Snail-egg 6300 Inorganic 24-hr LC50 Rehwoldt et al. 1973 Mussels 7390 Inorganic 24-hr LC50 WHO 1989


NOAEL and Effect Levels of mercury in the tissues of aquatic macroinvertebrates and fish are shown in

Table 3.3.2. Tissue mercury concentrations of 2680 ppb (ww) impaired the escape behavior of fish.

Reported NOAEL values range from 67 to 8000 ppb (ww) for fish tissue. NOAEL values for

macroinvertebrate tissue range from 10 to 5500 ppb (ww). No Effect Levels for macroinvertebrates

were located. A benchmark tissue concentration of 2000 ppb (ww) was selected for both fish and

macroinvertebrates based on these values. This concentration is within the reported NOAEL range for

fish and macroinvertebrates and is less than the Effect Levels for fish of 2680 ppb (ww).

FINAL


Table 3.3.2 NOAEL and Effect Levels of Mercury in Aquatic Biota Tissue

Species ppb (ww) Notes Tissue Type Effect Reference FISH- NOAEL

Common Carp 67 Methyl Hg Not specified Normal background VonBurg and Greenwood 1991 Common Carp 70 Total Hg Not specified Normal background VonBurg and Greenwood 1991 Fish 200 Total Hg Muscle Normal background Fimreite and Reynolds 1973 Lake whitefish 280 Total Hg Whole(less head) Normal background Uthe and Bligh 1971 Northern pike 440 Total Hg Whole(less head) Normal background Uthe and Bligh 1971 Northern pike 1000 Methyl Hg Muscle Normal Fimreite and Reynolds 1973 Brook trout 2700 Total Hg Whole body No effect Spry and Wiener 1991 Fish 4000 Total Hg Whole body Normal background Ewers 1991 Pike 8000 Methyl Hg Whole body Not poisoned Lockhart et al. 1972 Northern pike 8000 Methyl Hg Whole body Not poisoned Lockhart et al. 1972

FISH- EFFECT LEVELS Mosquitofish 2680 Total Hg Whole body Impaired escape behavior Kania and O’Hara 1974 Pike 5000 Total Hg Muscle Chronic lethal Fimreite and Reynolds 1973 Walleye 5000 Total Hg Muscle Chronic lethal Fimreite and Reynolds 1973 Fathead minnow 5440 Total Hg Whole body Reduced growth and

deformities Snarski and Olson 1982

Brook trout 15000 Total Hg Whole body Lethal Spry and Wiener 1991 Rainbow trout 26000 Total Hg Liver Toxic Matida et al. 1971 Trout 76000 Total Hg Whole Equilibrium loss Matida et al. 1971 Fish 100000 Total Hg Whole body Toxic Spry and Wiener 1991 Trout 112000 Total Hg Muscle Equilibrium loss Matida et al. 1971 Trout 272000 Total Hg Liver Equilibrium loss Matida et al. 1971

MACROINVERTEBRATES - NOAEL Crayfish 10 Total Hg Gill NOAEL Wright et al. 1991 Crayfish 15 Total Hg Muscle NOAEL Wright et al. 1991 Mayfly 18 Methyl Hg whole NOAEL Mason et al. 2000 Crayfish 30 Total Hg Hepatopancreas NOAEL Wright et al. 1991 Dragonfly 45 Methyl Hg whole NOAEL Mason et al. 2000 Shredder stonefly 48 Methyl Hg whole NOAEL Mason et al. 2000 Freshwater shellfish 2800 Total Hg Whole No effect Ewers 1991 Mayfly nymph 5500 Total Hg Whole NOAEL Saouter et al. 1991


3.4 Benchmark Summary

The benchmark values established from the literature review are summarized in Table 3.4.1.

FINAL


Table 3.4.1 Summary of Benchmark Mercury Concentrations

Receptor type Benchmark type ppb ww/dw Human Drinking water 1 ww Non-methyl dietary 1600 ww Methyl dietary 300 ww Terrestrial mammals Drinking water 1 ww Non-methyl dietary 2000 dw Methyl dietary 1100 dw Tissue concentration 3700 dw Birds Drinking water 1 ww Non-methyl dietary 4000 dw Methyl dietary 2500 dw Tissue concentration 6000 dw Terrestrial insects Tissue concentration 150 ww Terrestrial plants Soil concentration 10000 dw Tissue concentration 3000 dw Fish Water concentration 0.2 ww Tissue concentration 2000 ww Aquatic macroinvertebrates Water concentration 0.2 ww Tissue concentration 2000 ww

FINAL


4.0 EXPOSURE ASSESSMENT Site-specific sampling was the primary component of the exposure assessment portion of the RA. There

are several sources of data on mercury concentrations in abiotic (soil and water) and tissue samples from

the spill area. Some of the data utilized were collected as part of the spill response and remediation

activities, whereas other data were collected specifically to support the risk assessment. The different

sampling efforts that were utilized to evaluate exposure are discussed in greater detail below.

In addition to the discussed sampling efforts, additional sampling was conducted by Peruvian governmental

agencies or their consultants as part of the Governments’ response to the spill. These data are provided in

Appendix B. Due to several concerns with the validity of this sampling, the data are not utilized in the

Exposure Assessment of the RA. Primary concerns with the data are: 1) a lack of information on

sampling locations and methodologies, 2) inconsistent and insufficient reporting of analytical results, 3)

concerns with the analytical methods and detection sensitivity. As examples of these concerns, for many

of the samples only very general information is provided on sampling location (e.g., fish collected in the

Jequetepeque); additionally, a large number of samples are reported at a concentration of 0.0000 ppb. It is

unclear if these samples were below the detection limit, which is undefined, or if they are misreported.

Additionally, there is no information on the quality assurance and quality control (QA/QC) procedures

utilized in the analytical work. Finally, it is not stated if the results listed in the reports are reported on a

dry weight or wet weight basis.

Efforts were made to resolve concerns with this dataset, including extensive conversations with Dra.

Anaya, the Director of the Centro De Informacion Control Toxicologica (CICOTOX) laboratory. These

efforts, however, failed to resolve the primary concerns with the validity of the collected data. Though it

was determined that the dataset could not be used for the RA, in order to utilize the information gathered

by the SENASA sampling, a subsequent round of sampling was conducted jointly by SENASA, MYSRL,

and Shepherd Miller personnel in November 2000 at the locations where the earlier SENASA sampling

had reported elevated concentrations of mercury in plant tissue. The results of this sampling are discussed

in Section 4.3.

FINAL


4.1 Sampling Associated with Remediation and Monitoring

The water and sediment sampling program supporting the remediation and clean-up activities was

designed such that samples would be collected weekly for the first month following the spill or after

significant rainfall events. Sampling frequency was less intense during subsequent months, with at least

monthly water and sediment sampling for the first year following the spill to assess mercury mobility in the

natural waterways. Additional discussion of this sampling can be found in MYSRL (2001).

Water and sediment sample collection was initiated on June 15, 2000, from most of the locations listed in

Table 4.1.1. Sampling was also conducted the following week (June 22). Sampling locations are shown on

Map 2. As indicated in Table 4.1.1 and on Map 2, the locations labeled as ‘Reference’ were collected

from sites that were outside of the potential exposure areas, and are therefore reflective of background

conditions in the area. Samples from the June 15 and June 22 sampling events were sent to a local

Peruvian laboratory (Envirolab-Peru S.A.C.) for analysis. The analytical results of the sediments from

Envirolab were acceptable, but all of the reported mercury concentrations in water samples were below

Envirolab’s detection limit of 400 ng/L (0.4 ppb). In order to quantify the mercury concentrations,

subsequent water and sediment analyses were completed by Frontier Geosciences in Seattle, Washington,

USA, utilizing Cold Vapor-Atomic Fluorescence Spectrometry (CV-AFS) because of its increased

analytical sensitivity and the resulting lower detection limits.

Water and sediment samples were collected weekly for the first month following the spill (samples were

collected on June 15, June 22, June 28, and July 3) to determine if mercury was being transported down

the drainages immediately following the spill. Water and sediment samples were collected every two

weeks for the subsequent month (July 12 and August 2). Monthly sampling occurred again in September

(on September 2). Late in the dry season (e.g., August and September) many of the sampling locations

were dry and no samples were collected.

FINAL


Table 4.1.1 Water and Sediment Sampling Locations

Sampling Code Stream Name Sampling Description Road Km Site type RHUAC Rio Huacraruco Upstream San Juan NA Reference MCNG Q. Gavilan Upgradient Road, km 162 162 Reference QCHO-0 Q. Choten Upgradient Road, km 155 155.5 Reference DITCH-155 Km 155 Road Ditch Discharge Downgradient from km 155 loss area 155 Exposed QCHO-1 Q. Choten Downgradient Road, km 155 155 Exposed QCHO-2 Q. Choten Downgradient from highway crossing 154.5 Exposed WKM144.7 Surface drainage crossing Downgradient of Road at km 144.7 144.7 Exposed RSJ Rio San Juan Downgradient from San Juan 140.5 Exposed RLT Rio La Tranca Downgradient from road 140 Exposed RLTC Rio La Tranca Upgradient from road 140 Reference RCHO-1 Rio Choten Upgradient from road 133.5 Reference WKM-133.1 Km 133.1drainage Downgradient from km 133.1 133.1 Exposed RCHO-2 Rio Choten Downgradient from road 133 Exposed RJEQUE-0 Rio Jequetepeque Downgradient from Rio Choten confluence 132.5 Exposed WKM130.9 Ditch Irrigation water Irrigation Culvert drainage beside Site 8 130.9 Exposed WKM130.9 Irr Irrigation water Irrigation Ditch (off culvert) beside Site 8 130.9 Exposed RCUM-1 Rio Cumbe Upgradient of Road 130 Reference RCUM-2 Rio Cumbe Downgradient of Road 130 Exposed RJEQUE-1 Rio Jequetepeque Downgradient of the Rio Cumbe/

Rio Jequetepeque confluence 128.5 Exposed

S10-11-ID-1 Irrigation water Irrigation ditch above Sites 10 and 11 128.5 Reference S10-11-ID-2 Irrigation water Irrigation ditch below Sites 10 and 11 128..5 Exposed TIN-1 Spring Upgradient Road, km 127 127 Reference TIN-2 Spring Downgradient Road, km 127 127 Exposed QJOR-1 Q. Jordan Upgradient Road, km 126.5 126.5 Reference QJOR-2 Q. Jordan Downgradient Road, km 126.5 126.5 Exposed AMP Potable Water at Residence Choropampa Residence 126 Exposed AP-ET-CHOROP Potable Water Upgradient Choropampa water supply 126 Reference AP-ST-CHOROP Potable Water Choropampa water supply 126 Reference CHOPOS Potable Water at Posta Medica Choropampa Posta Medica 126 Exposed CHOCOL Potable Water at School Choropampa School 126 Exposed LZAR Potable Water at Residence Choropampa Residence 126 Exposed RJEQUE-2 Rio Jequetepeque Downgradient from Choropampa 126 Exposed RSUC-1 Q. Succha Upgradient Road, km 125 125 Reference RSUC-2 Q. Succha Downgradient Road, km 125 125 Exposed QTALLAL-1 Q. Tallal Upgradient from road 121.5 Reference QTALLAL-2 Q. Tallal Downgradient from road 121.5 Exposed RJEQ-AHUA Rio Jequetepeque Downgradient from Q. Tallal confluence 121.5 Exposed DITCH-114 Magdalena Street Drainage 114.5 Exposed RCHI-1 Rio Chilango Upgradient Road, km 114 114 Reference RCHI-2 Rio Chilango Downsgradient Road, km 114 114 Exposed QTRI Q. Trinchera Downgradient Road, km 113 113 Exposed RAM-1 Rio Amelia Upgradient Road, km 112.5 112.5 Reference RAM-2 Rio Amelia Downgradient Road, km 112.5 112.5 Exposed RMAG113 Rio Jequetepeque Downgradient of Magdalena 110 Exposed RJEQUE-3 Rio Jequetepeque Downgradient from Magdalena 109 Exposed RJEQUE-PUNETE Rio Jequetepeque at Bridge near

Reservior 40 kilometers Downgradient of Magdalena 80 Reference

RJEQUE-RES Rio Jequetepeque at Gallito Ciego Reservoir

45 kilometers Downgradient of Magdalena 75 Reference

FINAL


Several weeks of early season rains occurred between the middle of September and the beginning of

October. Weekly sampling was resumed on September 18 to determine if these early season rains were

mobilizing mercury. Early wet season samples were also collected on September 25 and October 2 before

the rains stopped. After the October 2 sampling it did not rain again for over a month, therefore,

scheduled wet season sampling was postponed. Sampling returned to the monthly dry season schedule

until the wet season resumed. Samples were collected during the week of November 13. The rains

resumed at the end of November and three weeks of wet season sampling resumed on December 1.

Additional samples were collected weekly for three weeks (December 7, 14, and 21), and then once every

two weeks through January of 2001 (January 8 and 20). Subsequent samples were collected in 2001

starting on the following dates: March 1, May 1, May 25, July 4, August 1, August 25, October 25,

November 6, and December 6. These dates covered the end of the 1st wet season and the start of the 2nd

wet season after the spill. There have been two sampling efforts in 2002, conducted during the week of

January 6 and April 15.

Figure 4.1.1 shows each sampling location with the mean concentration of mercury in water, the number

of samples used to calculate the mean, and the maximum recorded concentration. Also shown are the

benchmark values established in Section 3 for drinking water (human, mammal, and bird) and for the

protection of aquatic biota. The supporting data for this figure are provided as Appendix C. For many

locations, the mean concentration is greater than the maximum concentration because for samples that

were below the detection limit (i.e., < 400 ng/L), the detection limit was used in calculating the mean. The

mean concentration across all of the Exposed locations, over all sampling dates, is 0.017 ppb. The mean

concentration across all of the Reference locations, over all sampling dates, is 0.017 ppb. The mean

sediment mercury concentrations from the locations listed in Table 4.1.1, are shown in Figure 4.1.2, along

with the number of samples used to calculate the mean. The supporting data for this figure are provided

as Appendix D. The mean sediment mercury concentration across all of the Exposed sample locations,

over all of the sampling dates, is 112.4 ppb (dw). The corresponding mean for the Reference locations is

177.9 ppb (dw).

21 24 24 17 23 24 7 17 6 8 22 22 22 18 2 1 2020 23 7 9 22 22 23 25 22 21 13 25 20 22 21 23 2 20 22 25 20 20 20 19 25 19 18

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O-1

WK

M-1

33.1

RC

HO

-2

RJE

QU

E-0

WK

M-1

30.9

Ditc

h

WK

M-1

30.9

IRR

**R

CU

M-1

RC

UM

-2

RJE

QU

E-1

**S1

0-11

-ID

-1

S10-

11-I

D-2

**T

IN-1

TIN

-2

**Q

JOR

-1

QJO

R-2

**A

P-E

T-C

HO

RO

P

**A

P-ST

-CH

OR

OP

CH

OPO

S

RJE

QU

E-2

**R

SUC

-1

RSU

C-2

**Q

TA

LL

AL

-1

QT

AL

LA

L-2

RJE

Q-A

HU

A

DIT

CH

-114

**R

CH

I-1

RC

HI-

2

QTR

I

**R

AM

-1

RA

M-2

RM

AG

-113

RJE

QU

E-3

**R

JEQ

UE

-PU

EN

TE

**R

JEQ

UE

-RE

S

Site

Hg

(dis

solv

ed) p

pb

Average (including non-detects as MDL)Maximum Value (excluding non-detects)

US EPA and Peru Drinking Water Standard = 2.0 ppb

Aquatic Biota Water Benchmark = 0.2 ppb

Note: Maximum values are measured values excluding non-detects. Averages include all non-detects values of <0.4 as the value 0.4. The number above each bar is the number of results that went into the average calculation. **Denotes Reference Sites.

Drinking Water Benchmark for all terrestrial animals= 1.0 ppb

Project:

File:

Date: NOVEMBER 2002

100673

MERC-CHARTS.dwg

FIGURE 4.1.1DISSOLVED MERCURY CONCENTRATION IN

WATER SAMPLES AT EACH SAMPLING LOCATION

18

18

221719

1818

26201732220202324

17

2521

201966

2225209919

23

22

228

9

20

9

2221

19

22

23

21-

200

400

600

800

1,000

1,200

1,400

1,600

RH

UA

C

MC

NG

QC

HO

-0

DIT

CH

-155

QC

HO

-1

QC

HO

-2

WK

M-1

44.7

RSJ

RLT

RLT

C

RC

HO

-1

WK

M-1

33.1

RC

HO

-2

RJE

QU

E-0

WK

M-1

30.9

Ditc

h

WK

M-1

30.9

IRR

RC

UM

-1

RC

UM

-2

RJE

QU

E-1

S10-

11-I

D-1

S10-

11-I

D-2

TIN

-1

TIN

-2

QJO

R-1

QJO

R-2

AP-

ST-C

HO

RO

P

RJE

QU

E-2

RSU

C-1

RSU

C-2

QT

AL

LA

L-1

QT

AL

LA

L-2

RJE

Q-A

HU

A

DIT

CH

-114

RC

HI-

1

RC

HI-

2

QTR

I

RA

M-1

RA

M-2

RM

AG

-113

RJE

QU

E-3

RJE

QU

E-P

UE

NT

E

RJE

QU

E-R

ES

Site

Hg

ppb

Exposed Sites

Reference Sites

M.Y.S.R.L Remediation Goal 1,000 ppbNumber above the mean value equals thenumber of samples in the average calculation

FIGURE 4.1.2AVERAGE MERCURY CONCENTRATION OF

SEDIMENT SAMPLES

Project:

File:

Date: NOVEMBER 2002

100673

MERC-CHARTS.dwg

FINAL


4.2 Phase I (Year 2000) Sampling Conducted In Support of the Risk Assessment A sampling program was designed to specifically support the RA. The sampling design and protocols to

be utilized in conducting the sampling were presented to Dr. Peter M. Chapman, an independent third

party reviewer, prior to the collection of samples. Dr. Chapman was identified early in the risk

assessment process as a qualified individual who could provide an independent review of the RA and its

findings. Soil, vegetation, terrestrial insects, fish, and aquatic macroinvertebrates were collected at

reference locations outside of the influence of the spilt mercury, and at locations that were potentially

exposed to mercury. There are two phases to this sampling. Phase I collected samples in 2000, prior to

the occurrence of a wet season, which could mobilize the mercury. Phase II sampling was conducted in

2001-2002 after the end of the first post-spill wet season. Results of the Phase II sampling are discussed

in Section 4.4. All of the samples that were collected to specifically support the risk assessment were

analyzed by Frontier Geosciences (Seattle, WA, USA). Original laboratory reports have been previously

supplied to the Ministry of Energy and Mines (MEM).

4.2.1 Terrestrial Sampling and Tissue Analysis Sampling locations were selected to allow for the analysis of mercury movement, as well as to establish

relative baseline conditions around the spill locations. It was assumed that movement of mercury from the

points of spill along the roadway to adjacent terrestrial systems, if it occurred, would be by either or both

of two vectors: water and road dust. Therefore, at each location, sampling was performed within the

migration route starting near the spill location to areas more distant, but still within the identified potential

migration route. Additionally, at several locations, sampling was performed upgradient of the spill location,

in areas that could not be impacted by the spill (i.e., Reference Sites).

At each terrestrial sampling location (Map 3), soil, aboveground portions of plants, and insects were

collected. All samples were co-located to allow for the analysis of mercury transport in the system. For

agricultural crops, the sampled plant material was divided into different tissue types, with particular

emphasis placed on collection of edible plant tissue (e.g., tomato fruit and corn kernels). Additionally,

tubers were collected, when available, at the specific sampling locations. Each collected species (and

species tissue in some cases) was bagged separately. Soil samples were collected using a stainless steel

trowel to a depth of 20 cm. Soil was composited over the entire 20 cm depth. A depth of 20 cm was

selected as representative of the shallow root system, which would most likely be impacted by surficial

mercury contamination. Insects were collected using insect sweeps at each sampling location. Target

FINAL


collection amounts were 20+ grams for plants, 50 grams for soil, and 2+ grams for insects. Sampling

equipment was cleaned between samples by scrubbing with detergent water, followed by two de-ionized

water rinses. Samples were placed in Ziploc bags, labeled with Site number, sample number, sample type

(scientific name for plants), tissue type (total, leaves, fruit, etc.), and date collected and then wrapped in

aluminum foil. Samples were kept in coolers for less than 12 hours, until they could be frozen in dedicated

freezers.

The terrestrial sampling was conducted by Homero Bazan of the Colegio de Biologos del Peru and

Manual Cabanillos and Alfonso Miranda of the Universidad Nacional de Cajamarca. Overall, 154 plant

samples, 45 insect samples, and 48 soil samples were collected in September 2000. Descriptions of

sampling locations, samples collected at each location, and pictures of sampling sites provided by Professor

Bazan are included as Appendix E.

The U.S. Environmental Protection Agency (USEPA 1992) recommends using the 95 percent upper

confidence limit (95% UCL) of the mean for estimating exposure. The 95% UCL is calculated by the

following equation:

95% UCL= x + t (s/q n); where x is the mean value, t is the one -sided t statistic, s is the standard deviation and n is the number of samples used to calculate the mean

For the results of all of the sampling conducted in support of the risk assessment, the 95% UCL of the

mean is utilized as a conservative estimate of the true mean.

Soil Analyses

Results of the soil sampling are shown in Table 4.2.1. The results are broken-out by location and by site

type (Reference Site or Exposed Site samples). Site names reflect Identified Spill Locations (i.e., Spill

Locations 1-15, Map 1) or in the case of A, B, and C, locations where visible mercury was not observed,

but surveys identified elevated mercury levels (MYSRL 2001). Reference Sites listed in Table 4.2.1 are

from locations near the actual spill locations, but up-gradient of potential mercury migration routes.

FINAL


Table 4.2.1 Results of the Phase I Soil Samples

Site Road Km

Location Type

Sample ID

Total Hg (ppb, dw)

15-2 119.73 Reference 15-2-SOIL 9.70 15-3 119.73 Reference 15-3-SOIL 27.3 14-4 123.89 Reference 14-4-SOIL 39.8 13-6 124.77 Reference 13-6-SOIL 82.8 6-3 135.39 Reference 6-3-SOIL 39.3 6-4 135.39 Reference 6-4-SOIL 39.1 5-4 139.81 Reference 5-4-SOIL 21.0 1-3 155 Reference 1-3-SOIL 1130

15-1 119.73 Exposed 15-1-SOIL 16.5 14-1 123.89 Exposed 14-1-SOIL 27.1 14-2 123.89 Exposed 14-2-SOIL 48.6 14-3 123.89 Exposed 14-3-SOIL 34.9 13-1 124.77 Exposed 13-1-SOIL 58.7 13-2 124.77 Exposed 13-2-SOIL 21.4 13-3 124.77 Exposed 13-3-SOIL 59.4 13-4 124.77 Exposed 13-4-SOIL 68.5 13-5 124.77 Exposed 13-5-SOIL 33.0 10-1 128.94 Exposed 10-1-SOIL 25.9 10-2 128.94 Exposed 10-2-SOIL 18.7 10-3 128.94 Exposed 10-3-SOIL 794 8-1 130 Exposed 8-1-SOIL 33.4 8-2 130 Exposed 8-2-SOIL 47.7 8-3 130 Exposed 8-3-SOIL 57.4 8-4 130 Exposed 8-4-SOIL 20.1 8-5 130 Exposed 8-5-SOIL 112 8-6 130 Exposed 8-6-SOIL 7.68 8-7 130 Exposed 8-7-SOIL 26.2 8-8 130 Exposed 8-8-SOIL 75.9 8-9 130 Exposed 8-9-SOIL 57.9 7-1 134.45 Exposed 7-1-SOIL 30.1 7-2 134.45 Exposed 7-2-SOIL 12.9 7-3 134.45 Exposed 7-3-SOIL 34.0 7-4 134.45 Exposed 7-4-SOIL 98.1 6-1 135.39 Exposed 6-1-SOIL 91.9 6-2 135.39 Exposed 6-2-SOIL 53.4 5-1 139.81 Exposed 5-1-SOIL 58.8 5-2 139.81 Exposed 5-2-SOIL 45.7 4-1 140.18 Exposed 4-1-SOIL 49.2 4-2 140.18 Exposed 4-2-SOIL 74.1 B-1 145.433 Exposed B-1-SOIL 40.7 B-2 145.433 Exposed B-2-SOIL 29.3 C-1 145.455 Exposed C-1-SOIL 51.4 C-2 145.455 Exposed C-2-SOIL 33.7 A-1 147.423 Exposed A-1-SOIL 66.5 A-2 147.423 Exposed A-2-SOIL 40.6 1-1 155 Exposed 1-1-SOIL 197 1-2 155 Exposed 1-2-SOIL 156

FINAL


All of the collected soil samples (Figure 4.2.1) had reported mercury concentrations significantly below the

United States Environmental Protection Agency (USEPA) soil remediation standard for mercury of 10,000

ppb in residential soils (USEPA 1996), which is also equal to the benchmark established for soil that is

protective of plants (Section 3.2.2). The mean and 95% UCL of the mean dry weight mercury

concentration from the eight Reference Site samples were 173.6 and 432.9 ppb, with values ranging from

9.70 to 1130 ppb. The 1130 ppb value was from Sample 1-3, which was upgradient of Identified Spill

Location 1, and is much higher than the other concentrations at the Reference locations. The mean soil

concentration at the Reference Sites excluding this value was 37.0 ppb (dw) and the 95% UCL was 53.9

ppb (dw). The mean and 95 % UCL of the mean dry weight mercury concentration from the 39 Exposed

Sites were 72.0 and 105.6 ppb. Concentrations ranged from 7.68 to 794 ppb (dw). Only one of the 46

samples, from a Reference Site, exceeds (1130 ppb) the MYSRL remediation goal of 1000 ppb mercury in

soil. Overall, all of the measured soil concentrations were within concentrations representative of

background conditions for the region.

Figure 4.2.1 Scatterplot of Phase I soil Hg concentrations (dw) versus location

Vegetation Analyses

Results of the vegetation sampling are shown in Table 4.2.2. Results are first listed for Reference Sites

and then for Exposed Sites, on both a wet weight and dry weight basis. Approximate location along the

road (i.e., Road Km) is also indicated. The results are plotted in Figure 4.2.2, and summary statistics are

shown in Table 4.2.3.

0

2000

4000

6000

8000

10000

12000

110120130140150160

Road (Km)

So

il H

g (p

pb

) Reference Sites

Exposed Sites

USEPA soil limit=10000 ppb

To Cajamarca To Trujillo

MYSRL Remediation Goal=1000 ppb

Spill Area

Soil Benchmark= 10000 ppb

FINAL


Table 4.2.2 Results of the Phase I Vegetation Analyses

Sample Road Site English Spanish Veg. Dry Total Hg (ng/g) ID Km type Sci. Name Common name Common name Tissue1 Type Fraction wet wt dry wt

1-3-Baclat 155 Reference Baccharis latifolia Groundsel Chilca negra Forb 0.337 12.3 36.6 1-3-Bacsp 155 Reference Baccharis sp. Groundsel Chilca negra Forb 0.342 20.8 60.9 1-3-Indhoro 155 Reference Indigofora humilis Indigo Forb 0.283 13.0 46.1 5-4-Passp 139.81 Reference Paspalum sp. Paspalum Nudillo Grass 0.269 5.23 19.5 5-4-Polsp 139.81 Reference Polypogon sp. Beard grass Grass 0.472 8.97 19.0 6-3-Zeamay-fruit 135.39 Reference Zea mays Corn Maiz cob Grass 0.878 1.27 1.45 6-3-Zeamay-kernels 135.39 Reference Zea mays Corn Maiz kernels Grass 0.912 65.1 71.3 6-3-Zeamay-leaves 135.39 Reference Zea mays Corn Maiz leaves Grass 0.846 58.1 68.7 6-3-Zeamay-stalk 135.39 Reference Zea mays Corn Maiz stalk Grass 0.585 2.42 4.14 6-4-Acamac 135.39 Reference Acacia macracantha Porknut Huarango, Espino Tree 0.455 34.8 76.4 6-4-Altpor 135.39 Reference Alternanthera poirigens Joyweed Moradilla Forb 0.367 32.5 88.4 6-4-Crosp 135.39 Reference Croton sp. Croton Shrub 0.252 20.6 81.7 6-4-Schmol 135.39 Reference Schinus molle California pepper tree Tree 0.304 9.95 32.7 13-6-Bid 124.77 Reference Bidens pilosa Beggar's tick Cadillo Forb 0.321 55.6 173 13-6-Plamaj 124.77 Reference Plantago major Common plantain Llanten macho Forb 0.223 15.2 68.2 13-6-Trirep 124.77 Reference Trifolium repens White clover Trebol Forb 0.218 21.4 98.0 13-6-Verlit 124.77 Reference Verbena littoralis Verbena Verbena Forb 0.429 85.5 199 14-4-Eusp 123.89 Reference Euphorbia sp. Spurge Lecherita Forb 0.196 12.8 65.2 14-4-Schmol 123.89 Reference Schinus molle California pepper tree Molle Tree 0.381 38.9 102 14-4-Solnig 123.89 Reference Solanum nigrum Black nightshade Heirba mora Forb 0.220 20.2 92.0 15-2-Cheamb 119.73 Reference Chenopadium ambrosioides Mexican tea Paico Forb 0.232 8.95 38.6 15-2-Sonole 119.73 Reference Sonchus oleraceaus Sow thistle Cerraja Forb 0.217 5.49 25.3 15-3-Alltub 119.73 Reference Allium tuberosum Onion Cebolla china Forb 0.309 6.84 22.1 15-3-Arrxan 119.73 Reference Arracacia xanthorrihiga Peruvian carrot Arracacha Forb 0.168 6.47 38.5 15-3-Capfru 119.73 Reference Capsicum frutescens Cayenne pepper Aji verde fruit Forb 0.163 4.23 25.9 15-3-Corsat 119.73 Reference Conandrum sativum Coriander Culantro Forb 0.224 5.41 24.1

1-1-Pencla 155 Exposed Pennisetum claudestinum Kikuyu grass Kikuyu Grass 0.640 159 248 1-1-Plasp 155 Exposed Plantago sp. Plantain Llanten macho Forb 0.198 30.4 153 1-1-Verpar 155 Exposed Verbena parvula "verbena" Verbena Verbena Forb 0.244 85.6 351 1-2-Gasven 155 Exposed Gastridium ventricosum Nitgrass Grass 0.856 52.7 61.5 1-2-Junbuf 155 Exposed Juncus buffonius Toad rush Junco Forb 0.305 25.6 84.1 1-2-Trirep 155 Exposed Trifolium repens White clover Trebol blanco Forb 0.326 62.8 193 A-1-Metind 147.42 Exposed Melilotus indica Clover Trebol Forb 0.222 14.8 66.7 A-1-Oeosp 147.42 Exposed Oeonothera sp. Evening primrose Flor de cavo Forb 0.259 62.4 241 A-1-Trirep 147.42 Exposed Trifolium repens White clover Trebol blanco Forb 0.333 63.4 190 A-2-Dalsp 147.42 Exposed Dalea sp. Dalea Dalea Shrub 0.410 11.4 27.8 A-2-Medlup 147.42 Exposed Medicago lupulina Black medic Forb 0.320 10.0 31.3 A-2-Phyper 147.42 Exposed Physalis peruviana Peruvian groundcherry Tomate de bolsa Forb 0.222 12.7 57.3

FINAL


Table 4.2.2 Results of the Phase I Vegetation Analyses (continued)


C-1-Calsp 145.46 Exposed Calceolaria "globito" Pocket book plant Globito Forb 0.149 139 931 C-1-Escpen 145.46 Exposed Escallonia pendula Escallonia Pauco Tree 0.309 254 824 C-1-Stesp 145.46 Exposed Stevia sp. Stevia Forb 0.287 276 962 C-2-Hypsp 145.46 Exposed Hyptis sp. Mint weed Forb 0.389 27.2 69.9 C-2-Minsp 145.46 Exposed Minthostachys sp. Mint Chancua Shrub 0.481 107 223 C-2-Salopp 145.46 Exposed Salvia oppositiflora Peruvian salmon sage Salvia Forb 0.331 114 345 B-1-Escpen 145.43 Exposed Escallonia pendula Escallonia Pauco Tree 0.315 156 496 B-1-Phesp 145.43 Exposed Phenax sp. Phenax Shrub 0.298 9.55 32.1 B-1-Rhysp 145.43 Exposed Rhynchosia sp. Snoutbean Shrub 0.409 41.4 101 B-2-Baclat 145.43 Exposed Baccharis latifolia Groundsel Chilca negra Forb 0.353 19.9 56.2 B-2-Calsp 145.43 Exposed Calceolaria "globito" Pocket book plant Globito Forb 0.286 38.3 134 B-2-Pencla 145.43 Exposed Pennisetum claundestinum Kikuyu grass Kikuyo Grass 0.384 16.6 43.1 4-1-Medlup 140.18 Exposed Medicago lupulina Black medic Forb 0.326 246 753 4-1-Trisp 140.18 Exposed Trifolium sp. Clover Trebol Forb 0.307 263 858 4-2-Polavi 140.18 Exposed Polygonum aviculare Knotweed Forb 0.392 44.9 115 4-2-Rumsp 140.18 Exposed Rumex sp. Dock Forb 0.267 81.6 306 5-1-Penela 139.81 Exposed Pennisetum clandestinum Kikuyu grass Kikuyu Grass 0.285 41.4 145 5-1-Tareff 139.81 Exposed Taraxarum officinalis Dandelion Diente de leon Forb 0.292 77.2 265 5-2-Apilep 139.81 Exposed Apium leptophyllum "rulantillo" Wild celery Culantrillo Forb 0.216 12.3 56.8 5-2-Cyndac 139.81 Exposed Cyndon dactylon Bermuda grass Grama dulce Grass 0.417 28.3 68.0 5-2-Oxacor 139.81 Exposed Oxalis corniculata Creeping oxalis Vinagrillo Forb 0.229 38.8 170 5-3-Cheamb 139.81 Exposed Chenapodium ambrosioides Mexican tea Paico Forb 0.230 7.22 31.4 5-3-Phesp 139.81 Exposed Phenax sp. Phenax Shrub 0.234 6.89 29.5 6-1-Brosp 135.39 Exposed Browallia sp. Bush violet Forb 0.341 1930 5660 6-1-Caespi 135.39 Exposed Caesalpinia espinosa Spiny holdback Taya Tree 0.516 422 817 6-1-Pencla 135.39 Exposed Pennisetum clandestinum Kikuyu grass Grass 0.251 159 634 6-2-Lycsp 135.39 Exposed Lycopersicum sp. Tomato fruit Forb 0.270 46.7 173 6-2-Oxyvis 135.39 Exposed Oxybaphus viscosus Umbrella wort Forb 0.213 158 744 6-2-Penweb 135.39 Exposed Pennisetum weberbaueri Kikuyu grass Rabo de zorro Grass 0.505 122 243 7-1-Corsp 134.45 Exposed Cortaderia sp. Pampas grass Grass 0.433 210 485 7-1-Phycan 134.45 Exposed Phyla canescens Lippia Turre hembra Forb 0.645 275 426 7-2-Ammvis 134.45 Exposed Ammi visnaga Tothpick plant Visnaga Forb 0.326 46.8 144 7-2-Ophchi 134.45 Exposed Ophryosporus sp. Pilhuish Forb 0.494 146 296 7-2-Rhysp 134.45 Exposed Rhynchosia sp. Snoutbean Forb 0.434 115 265 7-3-Cheamb 134.45 Exposed Chenopodium ambrosioides Mexican tea Paico Forb 0.183 4.82 26.3 7-3-Plamaj 134.45 Exposed Plantago major Common plantain Forb 0.232 7.92 34.1 7-3-Rumsp 134.45 Exposed Rumex sp. Dock root Lengua de vaca Forb 0.213 6.07 28.5 7-3-Sacoff 134.45 Exposed Saccarum officinasum Sugar cane Cana de azucar leaves Grass 0.192 2.71 14.1

FINAL




7-4-Apilep 134.45 Exposed Apium leptophyllum Wild celery Forb 0.311 47.1 152 7-4-Setsp 134.45 Exposed Setaria sp. Foxtail Grass 0.412 117 284 7-4-Sposp 134.45 Exposed Sporobulus sp. Dropseed Pasto negro Grass 0.486 89.0 183 8-1-Annche 130 Exposed Annona cherimola Custard apple Cherimoya Tree 0.292 48.2 165 8-1-Phycan 130 Exposed Phyla canescens Lippia Turre hembra Forb 0.227 412 1820 8-1-Viglut 130 Exposed Vigna luteola Dalrymple vigna Porotillo Forb 0.470 214 455 8-2-Adisp 130 Exposed Adiantum sp. Maidenhair fern Culatrillo Forb 0.424 85.3 201 8-2-Alltub 130 Exposed Allium tuberosum Onion Cebolla china Forb 0.177 8.80 49.7 8-2-Cheamb 130 Exposed Chenopodium ambrosioides Mexican tea Paico Forb 0.285 31.9 112 8-2-Taroff 130 Exposed Taraxicum officinalis Dandelion Diente de leon Forb 0.239 45.8 192 8-2-Vitvin 130 Exposed Vitis vinifera Grape Uva fruit Tree 0.218 61.9 284 8-3-Amicel 130 Exposed Amaranthus celosioides Amaranth Yuyo Forb 0.361 48.8 135 8-3-Crosp 130 Exposed Croton sp. Croton Forb 0.341 426 1250 8-3-Ophchi 130 Exposed Ophryosporus chilca Pilhuish Forb 0.435 103 237 8-4-Annche 130 Exposed Annona cherimola Custard apple Chirimoya Tree 0.200 15.2 76.1 8-4-Aruclon 130 Exposed Arundo donax Giant reed Carrizo Grass 0.179 0.44 2.47 8-4-Leonep 130 Exposed Leonitis nepentaefolia Lion's ear Pochequiro Forb 0.250 53.0 212 8-5-Altper 130 Exposed Alternanthera porrigens Joyweed Moradilla Shrub 0.320 91.8 287 8-5-Pencla 130 Exposed Pennisetum claundestinum Kikuyu grass Grass 0.262 13.8 52.7 8-5-Plasp 130 Exposed Plantago sp. Plantain Llanten macho Forb 0.216 16.8 77.8 8-6-Pencla 130 Exposed Pennisetum claundestinum Kikuyu grass Kikuyo Grass 0.218 19.0 87.0 8-6-Solnig 130 Exposed Solanum nigrum Black nightshade Huerba mora Forb 0.280 33.4 119 8-6-Sonole 130 Exposed Sonchus oleraceaus Sow thistle Cerraja Forb 0.183 8.00 43.7 8-7-Brosp 130 Exposed Browallia sp. Bush violet Forb 0.343 80.8 235 8-7-Cesaur 130 Exposed Cestrum auriculatum Jasmine Hierba santa Shrub 0.291 107 368 8-7-Salopp 130 Exposed Salvia oppositiflora Peruvian salmon sage Forb 0.355 46.8 132 8-8-Cyndac 130 Exposed Cyndon dactylon Bermuda grass Grama dulce Grass 0.534 82.3 154 8-8-Phycan 130 Exposed Phyla canescens Lippia Turre hembra Forb 0.407 680 1670 8-9-Annche 130 Exposed Annona cherimola Custard apple Chirimoya Tree 0.303 22.1 73.1 8-9-Budsp 130 Exposed Bauddleia sp. Butterfly bush Tree 0.276 1640 5940 8-9-Cessp 130 Exposed Cestrum sp. Jasmine Hierba santa Shrub 0.192 5.87 30.5 10-1-Echsp 128.94 Exposed Echinochloa sp. Cockspur Grass 0.249 30.3 122 10-1-Oxyvis 128.94 Exposed Oxybaphus viscosus Umbrella wort Forb 0.259 26.4 102 10-1-Rhyrep 128.94 Exposed Rhynchelitium repens Natal redtop Grass 0.352 10.0 28.4 10-2-Asccur 128.94 Exposed Asclepias curassavica Scarlet milkweed Flor de seda Forb 0.212 6.85 32.3 10-2-Bid 128.94 Exposed Bidens pilosa Beggar's tick Cadillo Forb 0.200 7.96 39.8 10-2-Lansp 128.94 Exposed Lantana sp. Lantana Lantana Shrub 0.260 19.4 74.7 10-3-Minsp 128.94 Exposed Minthostachys sp. Mint Muña Shrub 0.332 51.2 154 10-3-Oeosp 128.94 Exposed Oeonothera sp. Evening primrose Flor de clavo Forb 0.339 65.9 194 10-3-Plasp 128.94 Exposed Plantago sp. Plantain Llanten macho Forb 0.168 83.1 494

FINAL




10-3-Polsp 128.94 Exposed Polypogon sp. Beard grass Grass 0.324 71.3 220 13-1-Asccur 124.77 Exposed Asclepias curassavica Scarlet milkweed Flor de seda Forb 0.237 68.5 289 13-1-Cyndoc 124.77 Exposed Cyndon dactylon Bermuda grass Grama dulce Grass 0.280 18.2 65.0 13-1-Leanep 124.77 Exposed Leonitis nepentaefolia Lion's ear Ponchequiro Shrub 0.252 47.2 187 13-1-Monsp 124.77 Exposed Monnina sp. Monnina Palomilla Forb 0.232 60.8 262 13-2-Acamac 124.77 Exposed Acacia macracantha Porknut Huarango Tree 0.393 31.2 79.4 13-2-Altpor 124.77 Exposed Alternanthera porrigens Joyweed Moradilla Shrub 0.521 1120 2150 13-2-Cesaur 124.77 Exposed Cestrum auriculatum Jasmine Hierba santa Shrub 0.344 161 469 13-2-Crosp 124.77 Exposed Croton sp. Croton Shrub 0.325 984 3030 13-3-Annche 124.77 Exposed Annona cherimola Custard apple Chirimoya Tree 0.412 485 1178 13-3-Citlim-f 124.77 Exposed Citrus limon Lemon Limon fruit Tree 0.443 220 496 13-3-Citlim-l 124.77 Exposed Citrus limon Lemon Limon leaves Tree 0.196 2.47 12.6 13-3-Helsp 124.77 Exposed Heliotropium sp. Heliotroope Forb 0.316 39.8 126 13-3-Leonep 124.77 Exposed Leonitis nepentaefolia Lion's ear Ponchequiro Forb 0.292 26.0 89.1 13-4-Ammvis 124.77 Exposed Ammi visnaga Tothpick plant Visnaga Forb 0.227 7.75 34.2 13-4-Argsub 124.77 Exposed Argemone subfusiformis Mexican poppy Cardo santo Forb 0.176 3.87 22.0 13-4-Asccur 124.77 Exposed Asclepias curassavica Scarlet milkweed Flor de seda Forb 0.185 8.63 46.6 13-4-Cucdip 124.77 Exposed Cucumis dipsaceus Hedgehog Jaboncillo de campo Forb 0.178 28.6 161 13-5-Zeamay 124.77 Exposed Zea mays Corn Maiz Grass 0.892 3.46 3.88 13-5-Zeamay-fruit 124.77 Exposed Zea mays Corn Maiz fruit Grass 0.895 3.29 3.67 13-5-Zeamay-kernels 124.77 Exposed Zea mays Corn Maiz kernels Grass 0.953 61.1 64.2 13-5-Zeamay-leaves 124.77 Exposed Zea mays Corn Maiz leaves Grass 0.952 57.7 60.6 14-1-Ammvis 123.89 Exposed Ammi visnaga Tothpick plant Visnaga Forb 0.246 34.5 140 14-1-Medhyp 123.89 Exposed Medicago hyspide Bur clover Carretilla Forb 0.314 34.0 108 14-1-Phycan 123.89 Exposed Phyla canescens Lippia Turre hembra Forb 0.254 67.9 267 14-1-Riccon 123.89 Exposed Ricinus Communis Castor bean Higuerilla Tree 0.234 29.6 126 14-2-Bid 123.89 Exposed Bidens pilosa Beggar's tick Cadillo Forb 0.189 19.4 102 14-2-Densp 123.89 Exposed Denothera sp. Primrose Alfaltilla Forb 0.354 44.2 125 14-2-Melalb 123.89 Exposed Melilotus alba Clover Flor de clavo Forb 0.404 28.4 70.4 14-3-Ammvis 123.89 Exposed Ammi visnaga Tothpick plant Visnaga Forb 0.160 4.78 29.9 14-3-Asccur 123.89 Exposed Asclepias curassivaca Scarlet milkweed Flor de seda Forb 0.302 13.5 44.7 14-3-Cyndac 123.89 Exposed Cyndon dactylon Bermuda grass Grama dulce Grass 0.319 6.67 20.9 14-3-Datstr 123.89 Exposed Datura stoamonium Jimson weed Chamico Forb 0.160 3.15 19.7 14-3-Galcil 123.89 Exposed Galinsoga ciliata Hairy galinsoga Galinsoga Forb 0.261 11.9 45.7 14-3-Phavul 123.89 Exposed Phaseolus vulgaris Beans Frejol fruit Forb 0.260 4.26 16.4 14-3-Rornas 123.89 Exposed Rorripa nastartium aquaticum Watercress Berro Forb 0.110 4.15 37.7 14-3-Staarv 123.89 Exposed Stachys arrensis Field woundwort Supiquehua Forb 0.215 11.4 53.1 15-1-Althal 119.73 Exposed Alternanthera halimifolia Joyweed Yerba blanca Forb 0.290 73.8 255 15-1-Rueflo 119.73 Exposed Rueilla floribunda Mexican Petunia Shrub 0.319 57.5 180

1 aboveground tissue collected, unless specific tissue type noted

FINAL


Figure 4.2.2 Total Hg tissue concentrations in the Phase I vegetation tissues collected at

reference and exposed locations. Wet weight and dry weight values are plotted separately. The two values exceeding the human dietary benchmark are non-edible bush-violet and butterfly plants.

0

500

1000

1500

2000

2500

115125135145155

Location (Road Km)

tota

l Hg

(ppb

, ww

)

Reference samples

Exposed samples

Human Dietary Benchmark=1600 ppb

Spill Area


0

1000

2000

3000

4000

5000

6000

7000

115125135145155

Location (Road Km)

tota

l Hg

(p

pb

, dw

)

Reference samples

Exposed samples

Spill Area


Mammal Dietary Benchmark= 2000 ppb

Bird Dietary Benchmark= 4000 ppb

FINAL


Table 4.2.3 Summary Statistics for the Phase I Vegetation Sampling

mean 95%UCL range (ppb) (ppb) (ppb)

Reference wet weight 22.0 29.4 1.3-85.5 dry weight 60.7 76.5 1.45-199

Exposed wet weight 118.0 156.6 0.44-1930 dry weight 354.4 472.2 2.47-5940

Terrestrial Insect Analyses

Results of the insect tissue sampling are listed in Table 4.2.4. Results are listed by location along the road

and by the type of sample (Reference or Exposed).

Summary statistics are provided in Table 4.2.5. The dry weight tissue concentrations were calculated

based on the average dry fraction of the 14 samples analyzed for percent moisture. Insufficient sample

size prevented the analysis of all samples for percent moisture. A scatterplot of the measured insect

tissue mercury concentrations versus location along the road is shown in Figure 4.2.3. The insect tissue

benchmark of 150 ppb (ww) and the bird dietary benchmark of 4000 ppb (dw) are indicated on Figure

4.2.3.

FINAL


Table 4.2.4 Results of the Phase I Insect Tissue Sampling

Sample Dry Total Hg, ppb ID Road Km Site type Fraction wet wt basis dry wt basis

1-3 Insects 155 Reference NA 13.7 - 5-4 Insects 139.81 Reference 0.41 21.1 51.8 6-3 Insects 135.39 Reference NA 49.9 - 6-4 Insects 135.39 Reference NA 35.0 - 13-6 Insects 124.77 Reference NA 53.6 - 14-4 Insects 123.89 Reference NA 118 - 15-2 Insects 119.73 Reference 0.39 9.51 24.3 15-3 Insects 119.73 Reference NA 19.9 -

1-1 Insects 155 Exposed NA 19.8 - 1-2 Insects 155 Exposed NA 22.6 - A-1 Insects 147.423 Exposed 0.37 34.7 95 A-2 Insects 147.423 Exposed 0.32 40.4 126 C-1 Insects 145.455 Exposed NA 35.9 - C-2 Insects 145.455 Exposed NA 42.8 - B-1 Insects 145.433 Exposed 0.39 54.8 140 B-2 Insects 145.433 Exposed 0.41 46.0 113 4-1 Insects 140.18 Exposed 0.29 24.1 83.8 4-2 Insects 140.18 Exposed NA 33.1 - 5-1 Insects 139.81 Exposed NA 531 - 5-2 Insects 139.81 Exposed 0.35 39.6 112 5-3 Insects 139.81 Exposed 0.40 7.10 18.0 6-1 Insects 135.39 Exposed 0.40 2240 5550 6-2 Insects 135.39 Exposed NA 736 -

7-1,2 Insects 134.45 Exposed NA 63.2 - 7-3 Insects 134.45 Exposed NA 27.7 - 7-4 Insects 134.45 Exposed NA 61.1 - 8-1 Insects 130 Exposed NA 47.1 - 8-2 Insects 130 Exposed NA 28.2 - 8-3 Insects 130 Exposed NA 56.6 -

8-4,5,6 Insects 130 Exposed NA 34.6 - 8-7 Insects 130 Exposed NA 447 - 8-8 Insects 130 Exposed NA 105 - 8-9 Insects 130 Exposed NA 105 - 10-1 Insects 128.94 Exposed 0.33 25.1 75.4 10-2 Insects 128.94 Exposed NA 20.5 - 10-3 Insects 128.94 Exposed 0.57 21.3 37.5 13-1 Insects 124.77 Exposed NA 77.2 - 13-2 Insects 124.77 Exposed NA 133 - 13-3 Insects 124.77 Exposed NA 35.7 - 13-4 Insects 124.77 Exposed 0.31 23.0 73.8 13-5 Insects 124.77 Exposed NA 22.0 - 14-1 Insects 123.89 Exposed NA 44.6 - 14-2 Insects 123.89 Exposed NA 50.6 - 14-3 Insects 123.89 Exposed NA 29.9 - 15-1 Insects 119.73 Exposed 0.38 13.7 36.4

NA= not analyzed due to insufficient sample mass

FINAL


Table 4.2.5 Summary Statistics for the Phase I Insect Sampling

mean 95%UCL range (ppb, ww) (ppb, ww) (ppb, ww)

Reference wet weight 40.1 63.8 9.5-118

dry weight* 105.5 167.9 25-311 Exposed

wet weight 145.4 252.0 7.1-2240 dry weight* 382.6 663.2 18.7-5895

* calculated by dividing ww by 0.38

Table 4.2.6 lists the soil, vegetation, and insect tissue concentrations measured at the four sites with the

tissue mercury concentrations that exceed the terrestrial insect tissue benchmark of 150 ppb (ww; Section

3.2.1). Also shown in Table 4.2.6 are the mean soil, vegetation, and insect tissue concentrations across all

of the Reference and Exposed sites. The soil concentrations of mercury, at the four sites with high insect

mercury concentrations, are all relatively low. Additionally, with the exception of Site 6-1, the vegetation

concentrations of mercury at these sites are also equivalent to the average mercury concentration in

vegetation samples at the Exposed locations, but elevated relative to the Exposed Site concentrations.

Table 4.2.6 Comparison of Soil and Insect Tissue Concentrations (Phase I)

Site

Soil Hg (ppb, dw)

Vegetation1

Hg (ppb, ww) Insect Hg (ppb, ww)

8-7 26.2 78.2 447 6-1 91.9 837.0 2240 6-2 53.4 108.9 736 5-1 58.8 59.3 531

Average for all Reference Sites 173.6 22 40.1 Average for all Exposed Sites 72.0 118 145.4 1 value listed is the mean concentration for all plant samples at that location dw= dry weight ww= wet weight

FINAL


Figure 4.2.3 Scatterplot of mercury concentrations in insects versus location (Phase I). Wet

weight and dry weight values are plotted separately. 4.2.2 Sampling and Tissue Analysis of Aquatic Biota Fish and aquatic macroinvertebrate (i.e., aquatic insects) samples were collected by Duke Engineering

(Bellingham, Washington) and ENKON Environmental (Surrey, British Columbia). Fish and

macroinvertebrates were selected for sampling since they are integrators of mercury levels in lower

0

500

1000

1500

2000

2500

110120130140150160

Location(Road Km)

Inse

ct H

g (

pp

b, w

w) Reference samples

Exposed samples


Spill Area

Insect Tissue Benchmark=150 ppb

0

1000

2000

3000

4000

5000

6000

110120130140150160

Location (Road Km)

Inse

ct H

g (

pp

b, d

w)

Reference samples

Exposed samples


Spill Area


FINAL


trophic levels, as well as in the water column and sediments (Figure 2.3.2). Stated goals of the aquatic

sampling were to:

n

determine background concentrations of mercury in aquatic macroinvertebrates and fish in the surrounding waters (to be used as Reference Sites);

n determine concentrations of mercury in aquatic organisms within the impact zone (i.e.,

Exposed Sites); n

evaluate if there is a significant difference in mercury concentrations between the reference and exposed populations;

n evaluate if there a difference in accumulated concentrations of mercury in aquatic organisms

when comparing 2000 baseline information with 2001 post-rainy season data (Phase II). Sampling locations were established above, within, and below the impact area. In some cases the sites are

at the same locations where water quality and sediment were sampled. The seven zones delineated for

the study were as follows:

Zone 7: Rio San Juan, upstream of spill influence (Reference): 1 site

Zone 6: Upstream of the initial spill site (Km 155) on tributary to Rio Choten (Reference): 1 site

Zone 5: Upstream of Rio San Juan and below the initial spill site on Rio Choten (Km 155) (Exposed): 3 sites

Zone 4: From the lower end of Zone 7 on Rio San Juan downstream to its intersection with Rio Choten (Exposed): 1 site

Zone 3: From below the confluence of Rio Choten and Rio San Juan downstream to Magdalena (Exposed): 3 sites

Zone 2: Downstream from Magdalena to upstream end of the Gallito Ciego reservoir (Reference): 3 sites

Zone 1: Upper portion of the Gallito Ciego reservoir (Reference): 1 site and the Reservoir itself.

Sampling locations and zones are shown on Map 3. The first five sample locations (Zones 1 and 2) are

Reference locations (i.e., non-impacted) that are several kilometers downstream of any of the spill sites,

all of which occur between Km 155 and Km 114 (Magdalena). While these sites are downstream of the

spill, they are considered as Reference sites since sampling was conducted prior to any rainstorms that

could have mobilized the spilt mercury into the waterways. Locations 6-1 and 7-1 are above any of the

spill locations and are therefore Reference locations. The remaining sample locations are all within the

general area of the spill, and are considered to be Exposed Sites. Due to sampling conducted prior to any

rainfall events, these areas, however, are also unlikely to have been influenced by the spilt mercury during

initial sampling.

FINAL


Fish were collected using electroshockers. At each site, the collected fish were measured, placed

separately into Ziploc bags (as whole fish), labeled and placed in coolers. At the end of each day, the

Ziploc bags were wrapped in aluminum foil and then placed in dedicated freezers. Fish from the

Reservoir were collected by hook and line and bottle traps by a commercial fisherman. Macroinvertebrate

samples were collected by scrubbing rocks with brushes, and straining water through a collection net and

sieve, and then placed into Nalgene bottles or plastic Ziploc bags and frozen. Additional discussion of the

sampling methodology, along with photographs and information on habitat conditions at each site, are

included in Appendix F.

Aquatic Macroinvertebrate Tissue Analysis

Tissue concentrations for the composite macroinvertebrate samples (i.e., all species together) and

individual freshwater crabs are shown in Table 4.2.7. Both total and methylmercury concentrations are

shown on a dry weight and wet weight basis, as available. The higher of the methyl or total mercury

values are plotted in Figure 4.2.4. As shown in Table 4.2.7, the percent of the total mercury present in the

form of methylmercury in the macroinvertebrate samples ranged from 40 to 100%. Values greater than

100% reflect differences in the analytical methodology utilized to analyze for total versus methylmercury

(Appendix G).

Table 4.2.7 Mercury Concentration in Phase I Aquatic Macroinvertebrate Samples

Sample Road Location Dry

methyl Hg (ppb)

Total Hg (ppb)

methyl/

Sample ID Type1 Zone Site

Km type** Fraction ww dw ww dw total

Z1S1-B Composite 1 1 50 Reservoir 0.174 102 587 87.9 505 1.16 CRAB-1 Crab-whole 1 1 50 Reservoir NA 69.3 - 69.4 - 1.00 CRAB-2 Crab-whole 1 1 50 Reservoir NA 40.9 - 35.3 - 1.16 CRAB-3 Crab-whole 1 1 50 Reservoir NA 23.6 - 21.2 - 1.11 Z2S1-B Composite 2 1 61 Downstream 0.203 93.7 462 85 419 1.10 Z2S2-B Composite 2 2 76 Downstream 0.239 21.4 89.7 26.1 109 0.82 Z2S3-B Composite 2 3 94 Downstream 0.167 2.74 16.4 6.62 39.7 0.41 Z3S1-B Composite 3 1 115 Exposed 0.436 - - 11.6 26.6 - Z3S2-B Composite 3 2 126 Exposed 0.201 - - 16.4 81.6 - Z3S3-B Composite 3 3 132 Exposed 0.285 16.4 57.5 26.2 91.9 0.63 Z4S1-B Composite 4 1 134 Exposed 0.322 18.5 57.3 15.6 48.3 1.19 Z5S1-B Composite 5 1 133 Exposed 0.161 - - 26.1 162 - Z5S2-B Composite 5 2 153 Exposed 0.197 - - 23.1 117 - Z6S1-B Composite 6 1 157 Upstream 0.141 - - 44.6 316 - Z7S1-B Composite 7 1 165* Upstream NA - - 4.43 - -

1Composite= the analyzed sample is a composite of all of the macroinvertebrates collected at that site * Zone 7 Site 1 is located in an upstream tributary (Rio Huacraruca) of the Jequetepeque ** Sites listed as Reservoir, Downstream, and Upstream are Reference locations

FINAL


All of the macroinvertebrate samples had low mercury concentrations, as expected from natural mercury

levels in the environment. The highest values were from Site 1-1 (Gallito Ciego Reservoir) and Site 2-1,

both of which are several kilometers below the spill locations and could not have been influenced by the

spill at the time of collection, since no significant rainfall had occurred between the spill and the sample

collection. Summary statistics are provided in Table 4.2.8. To be conservative, for both the Reference

and Exposed locations, the higher of the total or methylmercury value for each sample was used to

calculate the mean values. For samples that had insufficient material to measure the percent moisture, the

average dry fraction of 0.23 from the other samples was used to derive a dry weight concentration.

Table 4.2.8 Summary Statistics for the Phase I Macroinvertebrate Sampling

No. Mean (ppb) 95% UCL (ppb) Range (ppb) Area samples ww dw ww dw ww dw

Spill Area 6 20.3 172.4 25.1 268.9 11.6-26.2 19.3-316 Upstream 2 24.5 54.1 151.3 299.7 4.43-44.6 26.6-81.6 Downstream 7 51.8 215.6 78.9 375.4 6.62-102 39.7-587 All non-spill (Reference) 9 45.7 179.7 67.8 304.9 4.43-102 26.6-587 All samples 15 35.6 176.8 49.3 253.2 4.43-102 19.3-587

FINAL


Figure 4.2.4 Mercury concentration in macroinvertebrates versus sampling location (Phase

I). The Spill Area is indicated by the marked line. Wet weight and dry weight values are plotted separately.

0

100

200

300

400

500

600

700

456585105125145165

Location (Road Km)

Hg

(p

pb

, dw

)

Composite samples

Individual crab samples

To TrujilloTo Cajamarca

Spill Area

Bird Methylmercury Dietary Benchmark= 2500 ppb

0

20

40

60

80

100

120

456585105125145165

Location (Road Km)

Hg

(ppb

, ww

)

Composite samples

Individual crab samples

To TrujilloTo Cajamarca

Spill Area

Human Dietary (MeHg) Benchmark= 300 Macroinvertebrate Tissue Benchmark= 2000

FINAL


Fish Tissue Analysis

All of the collected fish tissue data are shown in Table 4.2.9. Sampling was conducted at the same

locations as the macroinvertebrates were collected (see Map 3). However, fish were not present at some

of the locations where macroinvertebrates were collected. Fish were collected at five Exposed Sites

(Zones 3, 4, and 5) and five Reference Sites. Four of the Reference Sites where fish were collected are

downstream of the spill area (Zones 1 and 2), and one Reference Site (Zone 7) was upstream of the spill

in the Rio Huacraruca tributary of the Rio Jequetepeque. Some of the samples were collected in August

2000, with the remainder collected in December 2000. All of the samples were analyzed for total

mercury, and a portion of the samples was also analyzed for methylmercury, as shown in Table 4.2.9.

The analytical techniques used for the analysis of total and methylmercury differed significantly. This

difference in methods is likely responsible for the apparent discrepancy in many of the methylmercury

concentrations exceeding the measured total mercury concentrations in the analyzed samples. This

apparent discrepancy (i.e., methyl exceeding total mercury) is further discussed in Appendix G. For the

purpose of the RA, we have assumed that all of the mercury in fish is present as the methyl form and

have utilized the highest recorded mercury level (either the total or the methyl) for each sample in the risk

calculations and evaluations. The maximum mercury value for each sample, on a wet weight and dry

weight basis, is plotted versus location in Figure 4.2.5. If a sample did not have an associated percent

moisture value to calculate the dry weight basis, the mean of the other percent moisture values (0.24) was

used to calculate the dry weight concentration. The benchmark values established in Section 3 are also

shown on Figure 4.2.5.

FINAL


Table 4.2.9 Results of the Phase I Fish Analyses

Sample Length Tissue Sample Dry methyl Hg, ppb Total Hg, ppb Identification

Species (cm) Type Date

Zone Site Fraction wet wt dry wt wet wt dry wt

methyl/ total

Road Km

Notes

Cachuela#1 Cachuela 10 muscle Aug-00 1 1 N/A NR N/A 229 N/A 50 Reservoir Cachuela#1 Cachuela 10 head Aug-00 1 1 N/A NR N/A 69 N/A 50 Reservoir Cachuela#4 Cachuela 10 muscle Aug-00 1 1 N/A NR N/A 279 N/A 50 Reservoir Cascafe-1 Cascafe 33 muscle Aug-00 1 1 N/A NR N/A 605 N/A 50 Reservoir Cascafe-2 Cascafe 23 muscle Aug-00 1 1 N/A N/A N/A 185 N/A 50 Reservoir Cascafe-3 Cascafe 25 muscle Aug-00 1 1 N/A N/A N/A 293 N/A 50 Reservoir Cascafe-6 Cascafe 13 muscle Aug-00 1 1 N/A N/A N/A 114 N/A 50 Reservoir Cascafe-6 Cascafe 13 head Aug-00 1 1 N/A N/A N/A 40.9 N/A 50 Reservoir

Charcoca#1 Charcoca 7.9 whole Aug-00 1 1 N/A 62.7 N/A 64 N/A 0.98 50 Reservoir Charcoca-A Charcoca 11 muscle Aug-00 1 1 0.177 N/A N/A 233 1316 50 Reservoir Charcoca-B Charcoca 9 whole Aug-00 1 1 N/A 118 N/A 116 N/A 1.02 50 Reservoir Charcoca-D Charcoca 11 muscle Aug-00 1 1 0.189 N/A N/A 91.1 482 50 Reservoir Charcoca-F Charcoca 9 whole Aug-00 1 1 N/A 114 N/A 104 N/A 1.10 50 Reservoir Charcoca-H Charcoca 8 whole Aug-00 1 1 N/A 94.9 N/A 92 N/A 1.03 50 Reservoir

Nato-B Nato 10 muscle Aug-00 1 1 N/A N/A N/A 387 N/A 50 Reservoir Nato-C Nato 8 whole Aug-00 1 1 0.225 159 707 146 649 1.09 50 Reservoir Nato-E Nato 8 whole Aug-00 1 1 0.306 49.6 162 56.8 186 0.87 50 Reservoir Nato-G Nato 10 muscle Aug-00 1 1 0.253 N/A N/A 317 1253 50 Reservoir Nato-H Nato 9.5 whole Aug-00 1 1 0.239 185 774 155 649 1.19 50 Reservoir Nato-J Nato 9.7 whole Aug-00 1 1 0.25 199 796 182 728 1.09 50 Reservoir Life-6 Life 12 muscle Aug-00 1 1 0.238 N/A N/A 95.5 401 50 Reservoir Life-7 Life 17 muscle Aug-00 1 1 0.248 N/A N/A 185 746 50 Reservoir Life-9 Life 12 muscle Aug-00 1 1 N/A N/A N/A 112 N/A 50 Reservoir

Life-10 Life 17 muscle Aug-00 1 1 0.244 N/A N/A 265 1086 50 Reservoir Mojarra-2 Mojarra 13 muscle Aug-00 1 1 N/A N/A N/A 146 N/A 50 Reservoir Mojarra-3 Mojarra 13 muscle Aug-00 1 1 N/A N/A N/A 250 N/A 50 Reservoir Mojarra-5 Mojarra 15 muscle Aug-00 1 1 N/A N/A N/A 121 121 50 Reservoir Mojarra-8 Mojarra 16 muscle Aug-00 1 1 0.29 N/A N/A 120 414 50 Reservoir Mojarra-8 Mojarra 16 head Aug-00 1 1 N/A N/A N/A 95.6 N/A 50 Reservoir Pejerry-1 Pejerry 19 muscle Aug-00 1 1 0.212 N/A N/A 75.8 358 50 Reservoir Pejerry-3 Pejerry 20 muscle Aug-00 1 1 N/A N/A N/A 70 N/A 50 Reservoir Pejerry-3 Pejerry 20 head Aug-00 1 1 N/A N/A N/A 53.1 N/A 50 Reservoir Pejerry-6 Pejerry 15 muscle Aug-00 1 1 0.19 N/A N/A 47.4 249 50 Reservoir Pejerry-8 Pejerry 17 muscle Aug-00 1 1 N/A N/A N/A 57.2 N/A 50 Reservoir Picalon-4 Picalon 10 muscle Aug-00 1 1 0.194 N/A N/A 114 588 50 Reservoir

FINAL


Table 4.2.9 Results of the Phase I Fish Analyses (continued)

Sample Identification

Length Tissue Sample Dry methyl Hg, ppb Total Hg, ppb Notes

Species

(cm) Type Date

Zone Site

Fraction wet wt dry wt wet wt dry wt

Methyl/ Total

Road Km

Picalon-6 Picalon 10 muscle Aug-00 1 1 0.202 N/A N/A 422 2089 50 Reservoir Tilapia-2 Tilapia 30 muscle Aug-00 1 1 0.173 N/A N/A 82.4 476 50 Reservoir Tilapia-2 Tilapia 30 head Aug-00 1 1 0.214 N/A N/A 53 248 50 Reservoir Tilapia-4 Tilapia 21 muscle Aug-00 1 1 N/A N/A N/A 46.4 N/A 50 Reservoir Tilapia-6 Tilapia 13 muscle Aug-00 1 1 N/A N/A N/A 27.1 N/A 50 Reservoir

Tilapia-10 Tilapia 29 muscle Aug-00 1 1 N/A N/A N/A 29.7 N/A 50 Reservoir Life-ZIS1 -14 Life 14 muscle Dec-00 1 1 0.226 N/A N/A 230 1020 50 Reservoir

Mojarra-ZIS1 -21 Mojarra 21 muscle Dec-00 1 1 0.197 N/A N/A 127 646 50 Reservoir Mojarra-ZIS1 -21 Mojarra 21 head Dec-00 1 1 0.241 N/A N/A 71.3 296 50 Reservoir

Cascafe-ZIIS1 -10.2 Cascafe 10.2 muscle Dec-00 2 1 0.256 N/A N/A 85.6 334 61 Downstream Chalcoco-ZIIS1 -7.7 Charcoca 7.7 whole Dec-00 2 1 N/A 59.6 N/A 48.8 N/A 1.22 61 Downstream

Chalcocoa-ZIIS1 -7.8 Charcoca 7.8 whole Dec-00 2 1 N/A 105 N/A 84.3 N/A 1.25 61 Downstream Chalcoca-ZIIS1 -9.3 Charcoca 9.3 whole Dec-00 2 1 N/A 154 N/A 137 N/A 1.13 61 Downstream Cascafe-ZIIS1 -18.6 Cascafe 18.6 muscle Dec-00 2 1 0.214 N/A N/A 288 1350 61 Downstream Calcoca-ZIIS1 -10.0 Charcoca 10 whole Dec-00 2 1 N/A 108 N/A 101 N/A 1.07 61 Downstream Calcoca-ZIIS1 -10.2 Charcoca 10.2 muscle Dec-00 2 1 0.239 N/A N/A 136 571 61 Downstream Calcoca-ZIIS1 -10.8 Charcoca 10.8 muscle Dec-00 2 1 0.246 N/A N/A 161 656 61 Downstream Calcoca-ZIIS1 -10.8 Charcoca 10.8 head Dec-00 2 1 0.406 N/A N/A 63.3 156 61 Downstream Calcoca-ZIIS1 -12.2 Charcoca 12.2 muscle Dec-00 2 1 0.248 N/A N/A 178 716 61 Downstream Calcoca-ZIIS1 -12.8 Charcoca 12.8 muscle Dec-00 2 1 0.236 N/A N/A 208 883 61 Downstream Mojarra-ZIIS1 -19.2 Mojarra 19.2 muscle Dec-00 2 1 0.205 N/A N/A 206 1000 61 Downstream

Nato-ZIIS1 -8.5 Nato 8.5 whole Dec-00 2 1 N/A 302 N/A 257 N/A 1.17 61 Downstream Calcoca-ZIIS2 -7.1 Charcoca 7.1 whole Dec-00 2 2 N/A 114 N/A 101 N/A 1.13 76 Downstream Calcoca-ZIIS2 -7.8 Charcoca 7.8 whole Dec-00 2 2 N/A 160 N/A 135 N/A 1.18 76 Downstream Calcoca-ZIIS2 -9.3 Charcoca 9.3 whole Dec-00 2 2 N/A 148 N/A 145 N/A 1.02 76 Downstream Calcoca-ZIIS2 -9.8 Charcoca 9.8 whole Dec-00 2 2 N/A 151 N/A 136 N/A 1.11 76 Downstream

Life-ZIIS2 -10.3 Life 10.3 muscle Dec-00 2 2 0.222 N/A N/A 307 1380 76 Downstream Life-ZIIS2 -10.5 Life 10.5 muscle Dec-00 2 2 0.208 N/A N/A 311 1490 76 Downstream Life-ZIIS2 -10.5 Life 10.5 head Dec-00 2 2 0.289 N/A N/A 224 776 76 Downstream Life-ZIIS2 -11.9 Life 11.9 muscle Dec-00 2 2 0.234 N/A N/A 322 1380 76 Downstream Life-ZIIS2 -13.0 Life 13.0 muscle Dec-00 2 2 0.232 N/A N/A 346 1490 76 Downstream Nato-ZIIS2 -3.8 Nato 3.8 whole Dec-00 2 2 N/A 245 N/A 197 N/A 1.24 76 Downstream

Calcoca-ZIIS3 -6.6 Charcoca 6.6 whole Dec-00 2 3 N/A 71.4 N/A 56.1 N/A 1.27 94 Downstream Calcoca-ZIIS3 -7.7 Charcoca 7.7 whole Dec-00 2 3 N/A 24.0 N/A 13.9 N/A 1.72 94 Downstream Calcoca-ZIIS3 -8.8 Charcoca 8.8 whole Dec-00 2 3 N/A 29.9 N/A 28.6 N/A 1.05 94 Downstream

FINAL



Sample Length Tissue Sample Dry methyl Hg, ppb Total Hg, ppb Notes

Identification Species

(cm) Type Date Zone Site

Fraction wet wt dry wt wet wt dry wt

Methyl/ Total

Road Km

Calcoca-ZIIS3 -9.6 Charcoca 9.6 whole Dec-00 2 3 N/A 53.3 N/A 48.9 N/A 1.09 94 Downstream Life-ZIIS3 -11.1 Life 11.1 muscle Dec-00 2 3 0.241 N/A N/A 143 593 94 Downstream Life-ZIIS3 -11.2 Life 11.2 muscle Dec-00 2 3 0.277 N/A N/A 44.2 160 94 Downstream Life-ZIIS3 -12.2 Life 12.2 muscle Dec-00 2 3 0.199 N/A N/A 78.6 395 94 Downstream Life-ZIIS3 -17.8 Life 17.8 muscle Dec-00 2 3 0.224 N/A N/A 132 589 94 Downstream

Life-1 Life 14 muscle Aug-00 3 1 N/A N/A N/A 65.3 N/A 115 Exposed Life-1 Life 14 head Aug-00 3 1 N/A N/A N/A 33.1 N/A 115 Exposed Life-2 Life 13 muscle Aug-00 3 1 N/A N/A N/A 75 N/A 115 Exposed Life-4 Life 12.5 muscle Aug-00 3 1 0.207 N/A N/A 84.4 408 115 Exposed Life-5 Life 12 muscle Aug-00 3 1 0.229 N/A N/A 120 524 115 Exposed Nato-1 Nato 8.5 whole Aug-00 3 1 N/A 26.8 N/A 26.6 N/A 1.01 115 Exposed Nato-3 Nato 8.5 whole Aug-00 3 1 N/A 58.5 N/A 49.8 N/A 1.17 115 Exposed Nato-4 Nato 9.5 whole Aug-00 3 1 0.265 30.1 114 28.1 106 1.07 115 Exposed Nato-5 Nato 7.5 whole Aug-00 3 1 N/A 26.4 N/A 28.1 N/A 0.94 115 Exposed

Cascafe-1 Cascafe 18 muscle Aug-00 3 1 N/A N/A N/A 184 N/A 115 Exposed Charcoca-1 Charcoca 10 muscle Aug-00 3 1 N/A N/A N/A 81.1 N/A 115 Exposed Charcoa-2 Charcoca 7.5 whole Aug-00 3 1 N/A 21.7 N/A 21.9 N/A 0.99 115 Exposed Charcoca-3 Charcoca 7.5 whole Aug-00 3 1 N/A 45.2 N/A 35.6 N/A 1.27 115 Exposed Charcoca-4 Charcoca 8 whole Aug-00 3 1 N/A 25.2 N/A 19.3 N/A 1.31 115 Exposed Charcoca-5 Charcoca 7.5 whole Aug-00 3 1 N/A 39.6 N/A 29.5 N/A 1.34 115 Exposed

Nato-1 Nato 11 muscle Aug-00 3 2 N/A N/A N/A 124 N/A 126 Exposed Nato-2 Nato 14 muscle Aug-00 3 2 N/A N/A N/A 257 N/A 126 Exposed Nato-5 Nato 10 muscle Aug-00 3 2 N/A N/A N/A 99.7 N/A 126 Exposed Nato-8 Nato 8.5 whole Aug-00 3 2 N/A 47.3 N/A 36.2 N/A 1.31 126 Exposed Nato-9 Nato 10 muscle Aug-00 3 2 N/A N/A N/A 113 N/A 126 Exposed

Nato-10 Nato 8.5 whole Aug-00 3 2 N/A 30.2 N/A 26.2 N/A 1.15 126 Exposed Nato-14 Nato 6 whole Aug-00 3 2 N/A 25.5 N/A 19.4 N/A 1.31 126 Exposed Nato-15 Nato 5.5 whole Aug-00 3 2 N/A 18 N/A 19 N/A 0.95 126 Exposed

Charcoca-1 Charcoca 13.5 muscle Aug-00 3 2 N/A N/A N/A 236 N/A 126 Exposed Charcoca-2 Charcoca 11.5 muscle Aug-00 3 2 N/A N/A N/A 142 N/A 126 Exposed Charcoa-3 Charcoca 11 muscle Aug-00 3 2 N/A N/A N/A 181 N/A 126 Exposed Charcoca-3 Charcoca 11 head Aug-00 3 2 N/A N/A N/A 96.3 N/A 126 Exposed Charcoca-4 Charcoca 8.5 whole Aug-00 3 2 0.3 44.4 148 37.9 126 1.17 126 Exposed Charcoca-7 Charcoca 8 whole Aug-00 3 2 0.315 49.4 157 47.7 151 1.04 126 Exposed Charcoca-9 Charcoca 11.5 muscle Aug-00 3 2 N/A N/A N/A 154 N/A 126 Exposed

FINAL



Length Tissue Sample Dry methyl Hg, ppb Total Hg, ppb Sample Identification

Species (cm) Type Date

Zone Site Fraction wet wt dry wt wet wt dry wt

Methyl/ Total

Road Km

Notes

Charcoa-9 Charcoca 11.5 head Aug-00 3 2 N/A N/A N/A 43.4 N/A 126 Exposed Charcoca-10 Charcoca 7.5 whole Aug-00 3 2 N/A 43.9 N/A 31.6 N/A 1.39 126 Exposed Charcoca-11 Charcoca 6.5 whole Aug-00 3 2 0.315 112 356 74.5 237 1.50 126 Exposed

Calcoca-ZIIIS3 -3.5 Charcoca 3.5 whole Dec-00 3 3 N/A 34.3 N/A 28.7 N/A 1.19 132 Exposed Calcoca-ZIIIS3 -3.7 Charcoca 3.7 whole Dec-00 3 3 N/A 50.0 N/A 31.6 N/A 1.58 132 Exposed Calcoca-ZIIIS3 -4.7 Charcoca 4.7 whole Dec-00 3 3 N/A 28.8 N/A 31.1 N/A 0.93 132 Exposed Calcoca-ZIIIS3 -5.1 Charcoca 5.1 whole Dec-00 3 3 N/A 40.2 N/A 38.0 N/A 1.06 132 Exposed

Nato-ZIIIS3 -3.1 Nato 3.1 whole Dec-00 3 3 N/A 18.1 N/A 5.07 N/A 3.57 132 Exposed Nato-ZIIIS3 -3.6 Nato 3.6 whole Dec-00 3 3 N/A 40.2 N/A 34.3 N/A 1.17 132 Exposed Nato-ZIIIS3 -5.0 Nato 5.0 whole Dec-00 3 3 N/A 44.5 N/A 37.5 N/A 1.19 132 Exposed Nato-ZIIIS3 -9.7 Nato 9.7 whole Dec-00 3 3 N/A 38.6 N/A 33.2 N/A 1.17 132 Exposed

Nato-ZIIIS3 -12.6 Nato 12.6 muscle Dec-00 3 3 0.213 N/A N/A 75.4 354 132 Exposed Pejerry-ZIIIS3 -12.2 Pejerrey 12.2 muscle Dec-00 3 3 0.243 N/A N/A 125 515 132 Exposed Calcoca-ZIVS1 -4.8 Charcoca 4.8 whole Dec-00 4 1 N/A 35.0 N/A 33.9 N/A 1.03 134 Exposed

Nato-ZIVS1 -3.7 Nato 3.7 whole Dec-00 4 1 N/A 16.0 N/A 12.8 N/A 1.26 134 Exposed Nato-ZIVS1 -12.0 Nato 12.0 muscle Dec-00 4 1 0.211 N/A N/A 65.7 311 134 Exposed

Nato-1 Nato 10.5 muscle Aug-00 5 1 N/A N/A N/A 121 N/A 133 Exposed Nato-1 Nato 10.5 head Aug-00 5 1 N/A N/A N/A 76.4 N/A 133 Exposed Nato-2 Nato 10 muscle Aug-00 5 1 N/A N/A N/A 141 N/A 133 Exposed Nato-2 Nato 10 head Aug-00 5 1 N/A N/A N/A 73.3 N/A 133 Exposed Nato-3 Nato 6 whole Aug-00 5 1 N/A 76.6 N/A 53.2 N/A 1.44 133 Exposed Nato-4 Nato 10 muscle Aug-00 5 1 N/A N/A N/A 217 N/A 133 Exposed Nato-6 Nato 6.5 whole Aug-00 5 1 N/A 70 N/A 50.4 N/A 1.39 133 Exposed Nato-8 Nato 7.5 whole Aug-00 5 1 N/A 48.9 N/A 39.7 N/A 1.23 133 Exposed Nato-9 Nato 9 whole Aug-00 5 1 N/A 95 N/A 75.9 N/A 1.25 133 Exposed Nato-1 Nato 10 muscle Aug-00 7 1 N/A N/A N/A 58.7 N/A 165 Reference Nato-7 Nato 8.4 whole Aug-00 7 1 N/A 44.4 N/A 31.4 N/A 1.41 165 Reference Nato-9 Nato 9.4 whole Aug-00 7 1 0.281 77.5 276 49.8 177 1.56 165 Reference

Nato-13 Nato 10 muscle Aug-00 7 1 N/A N/A N/A 57.3 N/A 165 Reference Nato-13 Nato 10 head Aug-00 7 1 N/A N/A N/A 42.6 N/A 165 Reference Nato-17 Nato 4.2 whole Aug-00 7 1 N/A 20.9 N/A 14.8 N/A 1.41 165 Reference Nato-19 Nato 4.4 whole Aug-00 7 1 N/A 16.9 N/A 10.4 N/A 1.63 165 Reference

Samples listed as Reservoir, Downstream, or Upstream were collected at Reference locations N/A= not analyze

FINAL


Figure 4.2.5 Mercury concentration in fish at all sampling locations (Phase I). The Spill Area

is indicated by the marked line. Samples shown as collected at Km 165 are from a reference tributary upstream of the spill area. Wet weight and dry weight values are plotted separately.

0

100

200

300

400

500

600

700

406080100120140160180

Location (Road (Km)

Hg

(p

pb

, ww

)

Reference Locations

Exposed Locations

Spill Area

Human Methyl Dietary Benchmark= 300 ppb

Fish Tissue Benchmark= 2000 ppb


0

500

1000

1500

2000

2500

3000

3500

4000

406080100120140160180

Location (Road (Km)

Hg

(ppb

, dw

)

Reference Locations

Exposed Locations

Bird Methyl Dietary Benchmark= 2500

To Cajamarca To

Spill Area

FINAL


Summary statistics for Reference and Exposed samples are shown in Table 4.2.10.

Table 4.2.10 Summary Statistics for the Phase I Fish Sampling

No. Mean (ppb) 95% UCL (ppb) Range (ppb) Area samples ww dw ww dw ww dw

Spill Area 55 77.6 323.3 90.6 377.5 16.0-257 40-1071 Upstream (Reference) 7 45.5 189.6 61.3 255.4 16.9-77.5 70.4-325 Downstream (Reference) 75 156.5 652.1 177.5 739.6 24.0-605 100-2521 All non-spill (Reference) 82 147.0 612.5 167 695.8 16.9-605 70.4-2521 All samples 137 119.0 495.8 133 554 16.0-605 40-2521

Table 4.2.11 shows the results of the fish tissue analysis (ww) for each sample location.

Table 4.2.11 Mercury Concentration in Fish at Each Location (Phase I)

Mean 95% UCL Range Site Km Location Hg (ppb ww) Hg (ppb ww) Hg (ppb ww) 1-1 50 Reservoir 155.3(44) 185.6 27.1-605 2-1 61 Downstream 153.8 (13) 193.7 48.8-302 2-2 76 Downstream 232.8 (10) 282.4 114.2-346 2-3 94 Downstream 72.0 (8) 101.8 24.0-143 3-1 115 Exposed 61.2 (15) 81.3 21.9-184 3-2 126 Exposed 101.0 (18) 130.3 19.0-257 3-3 132 Exposed 49.7 (10) 67.3 18.1-125 4-1 134 Exposed 38.9 (3) 81.2 16.0-66 5-1 133 Exposed 102.1 (9) 133.4 48.9-217 7-1 165(1) Upstream 45.5 (7) 61.3 16.9-78

* values in parentheses indicate number of samples averaged (1) Zone 7 Site 1 (7-1) is located in an upstream tributary (Rio Huacraruca) Samples listed as Reservoir, Downstream, or Upstream were collected at Reference locations

In order to evaluate fish as consumed by the local human population, small fish (<10 cm) were analyzed as

whole fish, whereas larger fish (>10 cm) were segregated into muscle and head samples prior to analysis.

Table 4.2.12 shows the mean, 95% UCL, and range of the wet weight mercury concentrations across all

of the samples for each of these tissue types.

Table 4.2.12 Mercury Concentrations for Each Fish Tissue Type (Phase I)

Mean 95% UCL Range Tissue

Hg (ppb ww) Hg (ppb ww) Hg (ppb ww) Head 74.0 (14) 96.4 33.1-224 Muscle 165.4 (67) 187 27.1-605 Whole 75.1 (56) 89.3 16.0-302

Values in parentheses indicate number of samples averaged ww= wet weight

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Muscle tissue had the highest mercury concentrations (Table 4.2.12; Figure 4.2.6). This may be due to

larger fish being selected for muscle tissue analysis versus smaller fish for whole body analysis.

Generally, larger and older fish will have higher mercury concentrations than smaller and younger fish

(USEPA 1999a). However, a regression analysis indicated that there was no significant relationship

(R2<0.10) between fish length and mercury concentrations in fish tissue of the collected samples.

Figure 4.2.6 Mercury concentrations (ww) in each fish tissue type plotted versus fish length

(Phase I). Samples from both Reference and Exposed locations are included.

Table 4.2.13 shows the mean mercury concentrations in each tissue type (head, muscle, or whole fish) for

each of the analyzed fish species, across all sampling locations. There was significant variation between

the fish species. Much of this variation, however, may be due to the small number of samples analyzed

for each fish species. This is especially true for the head and whole body analyses. The mean mercury

concentrations in the heads of the different species ranged from 40.9 ppb (ww) to 128.6 ppb (ww).

Cascafe had the lowest mean concentration in heads and Life had the highest. In muscle tissue, Picalon

was the species with the highest mean concentration at 268 ppb (ww) and Tilapia had the lowest at 46.4

ppb (ww). Cascafe, which had the lowest mean mercury concentrations in head tissue (40.0 ppb ww), had

the third highest mean concentration in muscle tissue at 251 ppb (ww).

0

100

200

300

400

500

600

700

0 6 12 18 24 30 36Fish length (cm)

Hg

(ppb

)

Hg concentration in heads

Hg concentration in muscle

Hg concentration in whole fish

FINAL


Table 4.2.13 Mean Total Hg Concentrations for Each Fish Species and Tissue Type (Phase I)

Head Muscle Whole Species

Hg (ppb ww) Hg (ppb ww) Hg (ppb ww) Cachuela 69 (1) 254(2) ND Cascafe 40.9 (1) 251 (7) ND Charcoca 67.7 (3) 164 (11) 75.4 (29) Life 128.6 (2) 172 (17) ND Mojarra 83.4 (2) 162 (6) ND Nato 64.1 (3) 156 (13) 74.8 (27) Pejerrey 53.1 (1) 75.0 (5) ND Picalon ND 268 (2) ND Tilapia 53.0 (1) 46.4 (4) ND

ND= no data ww= wet weight Values in parenthesis indicate number of samples averaged

Smaller fish and lower trophic level species (i.e., herbivorous fish) might be expected to have the lowest

mercury concentrations. As shown in Table 2.2.2, Picalon, Tilapia, and Life are considered to only eat

plants (or detritus), whereas all of the other fish are believed to be omnivorous, eating both plants and

insects. Also shown in Table 2.2.2, is the size range (length) for each of the fish species. Overall, the

largest fish collected were Tilapia, which were only collected in the Gallito Ciego Reservoir, and Cascafe.

Cachuela, Charcoca, and Picalon tended to be the smallest fish collected. It was surprising that Picalon

had the highest mean muscle concentration, since they are small, herbivorous fish. It is important to note,

however, that only two samples were analyzed, so the results are not robust. Cascafe, which is one of the

species with larger fish analyzed, had very low head concentrations, but one of the higher mean muscle

concentrations. Tilapia, the other larger fish species analyzed, had very low head and muscle mercury

concentrations. Overall, however, the mean mercury concentration in all of the analyzed fish species was

low, and within ranges typical of fish in uncontaminated waters (Section 1.2.3; Sweet and Zelikoff 2001).

4.3 November 2000 Sampling (Shepherd Miller, SENASA, MYSRL)

Some limited sampling was conducted on November 15, 2000 by MYSRL, SENASA, and Shepherd Miller

personnel in and around Choropampa. The purpose of the sampling was to jointly revisit locations where

SENASA sampling (see Appendix B) had previously reported mercury concentrations above those

generally observed in the area. Specifically, samples were collected at three locations: 1) in or near Elias

Herrara’s fields between the road and the Jequetepeque River, 2) near the Juan Azanero residence in

Choropampa, and 3) on the farm of Ernesto Leon, approximately 0.5 Km to the southwest of

Choropampa. These locations are indicated on Map 4.

Results of the vegetation and soil analyses are shown in Table 4.3.1. SENASA personnel selected the

sampling locations and tissue types. For many of the sample locations, soil samples were collected directly

FINAL


beneath the sampled vegetation. However, not all of the vegetation samples have a corresponding co-

located soil sample, as directed by SENASA personnel.

Table 4.3.1. Results from the November 15, 2000 Plant and Soil Sampling

Sample Road Soil Vegetation Total Hg Total Hg Location No. Km ppb (dw) Type

Tissue ppb (ww) ppb (dw)

Herrara 1 128 1300 Yuca root 14.2 39.7 Herrara Yuca leaf 11.2 39.8 Herrara Yuca stem 2.65 11.4 Herrara 2 128 NA Yuca leaf 7.59 67.1 Herrara Yuca stem 3.39 18.7 Herrara 3 128 119 Potato stem 0.69 3.25 Leon 1 128 NA Alfalfa leaf 8.75 30.3 Leon 2 128 NA Avocado fruit < 0.62 <2.7 Leon Avocado leaf 12.1 39.4 Leon 3 126 17.0 Tomato leaf 5.43 29.5 Leon Tomato fruit 0.54 4.29 Leon Tomato root 3.04 14.7 Leon 4 126 61.8 Grape fruit 2.03 13.6 Leon Grape leaf 12.5 43.0 Azanero 5 127.5 537 Orange leaf 476 1690 Azanero Orange root 125 456 Azanero Orange stem 176 532 Azanero 6 127.5 358 Lemon fruit1 18.2 96.3 Azanero Lemon fruit-washed1 16.0 88.6 Azanero Lemon leaf 1950 6090 Azanero Lemon root 45.5 142 Herrara 7 128 246 Taya fruit 1.88 4.14 Herrara Taya leaf 4.40 11.5 Herrara Taya root 13.1 24.8

dw= dry weight ww= wet weight NA= not analyzed 1 This lemon sample was cut into two pieces; one half was washed prior to analysis and one half was not

Summary statistics for the soil and vegetation samples are provide in Table 4.3.2. Results of the

November sampling are similar to results from the Phase I sampling discussed in Section 3.2. The mean

wet weight concentration of mercury in the Phase I vegetation samples from Exposed locations was 118

ppb, with values ranging from 0.44 to 1930 ppb (ww).

Table 4.3.2 Summary Statistics for the November 15, 2000 Soil and Vegetation Samples

Mean (ppb) 95% UCL (ppb) Range (ppb) ww dw ww dw ww dw

Soil NA 377 NA 743 NA 17.0-1300 Vegetation 121 396 264 838 0.54-1950 2.7-6090 NA= not analyzed

The highest mercury value in vegetation, 1950 ppb (ww), was from a lemon leaf collected next to Juan

Azanero Mendoza’s house in Choropampa. However, both the fruit and root samples collected from the

FINAL


same tree had low mercury concentrations (18.2 ppb and 45.5 ppb ww respectively). The soil mercury

concentration under the tree was 358 ppb (dw). Due to the low root and fruit concentrations of mercury

at this sample location, it is unlikely that the elevated mercury concentration in the lemon leaf was a result

of plant uptake from contaminated soil. The recorded high value may have been due to surfic ial

contamination of the leaf surface. This site is across the street from the Medical Post, which is near the

single largest mercury spill location. Surficial contamination of this tree may have occurred prior to, or

during, remediation of the site and surrounding homes. The highest soil mercury concentration of 1300 ppb

(dw) was recorded at one location in Elias Herrara’s field. This value is higher than other recorded values

from the November sampling, but similar to a value of 1130 ppb measured at a Reference location in the

Phase I sampling (Section 4.2). A second sample from the same field had a mercury concentration of 128

ppb (dw), potentially indicating natural variability in soil concentrations.

Because the earlier sampling by SENASA (Appendix B) indicated that there were not significant

elevations of mercury in animal tissue near the spill locations, SENASA personnel directed the collection

of only limited animal tissue samples during the November 2000 re-sampling. Pig hair was collected from

two different animals at Juan Azanero’s house in Choropampa and the kidney and liver from a single

rabbit were sampled at Ernesto Leon’s farm. Results from the pig hair and rabbit organ sampling are

shown in Table 4.3.3. The values shown in Table 4.3.3 are indicative of expected normal background

levels (Table 1.2.3) and are below reported toxic levels in tissues (Table 3.2.3).

Table 4.3.3 Results from the November 15, 2000 Animal Tissue Sampling

Tissue Dry Total Hg (ppb) Sample ID Species* type Location Fraction ww basis dw basis

ELT-CON-H-1-DUP Rabbit-1 Kidney Leon 0.23 5.98 26.5 ELT-CON-R-1-DUP Rabbit-1 Liver Leon - 5.95 - JAM-POR-P-1-DUP Pig-1 Hair Azanero 0.89 151 170 JAM-POR-P-2-DUP Pig-2 Hair Azanero 0.84 94.1 112

ww= wet weight dw=dry weight * The liver and kidney were collected from the same rabbit, two different pigs were sampled for hair

4.4 Phase II Sampling Conducted In Support of the Risk Assessment

The results of the second phase (Phase II) of the sampling designed and conducted to specifically support

the risk assessment are presented and discussed in this section. Whereas the Phase I sampling (Section

4.2) was conducted in 2000, the Phase II sampling was conducted in 2001 and 2002, beginning after the

end of the first post-spill wet season. All of the samples that were collected in Phase II were analyzed by

Frontier Geosciences (Seattle, WA, USA). Original laboratory reports have been previously supplied to

the MEM.

FINAL


4.4.1 Terrestrial Sampling and Tissue Analysis The sampling locations for the Phase II sampling were identical to those discussed in Section 4.2 for the

Phase I sampling. At each terrestrial sampling location (Map 3), co-located soil, aboveground portions of

plants, and insects were collected. The Phase II terrestrial sampling, like the Phase I sampling, was

conducted by Homero Bazan of the Colegio de Biologos del Peru and Manual Cabanillos and Alfonso

Miranda of the Universidad Nacional de Cajamarca. Overall, 130 plant samples, 47 insect samples, and 48

soil samples were collected in February 2002. This sampling was originally scheduled to occur at the end

of the second dry season in September 2001, but due to delays in receiving necessary government permits,

sampling could not occur until after the wet season had started. Descriptions of sampling locations,

samples collected at each location, and pictures of sampling sites provided by Professor Bazan are

included as Appendix H.

Soil Analysis Results, broken-out by location and site type (Reference Site or Exposed Site samples), of the Phase II

soil sampling are shown in Table 4.4.1.

As shown in Figure 4.4.1, all of the soil samples collected in the Phase II sampling were below the soil

benchmark value of 10,000 ppb established in Section 3.3.2 and the MYSRL remediation goal of 1000 ppb

for soils. The mean and 95% UCL of the mean dry weight (dw) mercury concentration for soils at

Reference sites were 37.0 and 62.8 ppb. The corresponding values for the soils at Exposed sites were

50.4 ppb and 60.3 ppb. The range of recorded mercury concentrations was 11.5-131 ppb (dw) for

Reference soils and 8.56-149 ppb (dw) for soils at Exposed sites. All of the mercury concentrations

measured in soils during the Phase II sampling were below the remediation goal for soil clean-up and are

representative of background conditions.

FINAL


Table 4.4.1 Results of the Phase II Soil Samples

Site Road Km

Location Type

Sample ID

Total Hg (ppb, ww)

Total Hg (ppb, dw)

15-2 119.73 Reference 15-2-SOIL 9.73 11.5 15-3 119.73 Reference 15-3-SOIL 27.4 32.8 14-4 123.89 Reference 14-4-SOIL 21.7 26.0 13-6 124.77 Reference 13-6-SOIL 29.3 31.5 6-3 135.39 Reference 6-3-SOIL 16.4 20.6 6-4 135.39 Reference 6-4-SOIL 17.7 20.2 5-4 139.81 Reference 5-4-SOIL 19.1 22.3 1-3 155 Reference 1-3-SOIL 111 131

15-1 119.73 Exposed 15-1-SOIL 25.0 30.3 14-1 123.89 Exposed 14-1-SOIL 39.0 42.4 14-2 123.89 Exposed 14-2-SOIL 16.8 19.9 14-3 123.89 Exposed 14-3-SOIL 30.3 37.5 13-1 124.77 Exposed 13-1-SOIL 81.2 93.5 13-2 124.77 Exposed 13-2-SOIL 47.9 58.0 13-3 124.77 Exposed 13-3-SOIL 21.7 27.2 13-4 124.77 Exposed 13-4-SOIL 37.9 45.8 13-5 124.77 Exposed 13-5-SOIL 19.7 23.3 10-1 128.94 Exposed 10-1-SOIL 19.0 23.8 10-2 128.94 Exposed 10-2-SOIL 16.3 19.2 10-3 128.94 Exposed 10-3-SOIL 19.3 21.9 8-1 130 Exposed 8-1-SOIL 72.2 86.7 8-2 130 Exposed 8-2-SOIL 63.6 82.0 8-3 130 Exposed 8-3-SOIL 59.6 73.9 8-4 130 Exposed 8-4-SOIL 39.5 50.2 8-5 130 Exposed 8-5-SOIL 12.5 14.7 8-6 130 Exposed 8-6-SOIL 27.4 34.1 8-7 130 Exposed 8-7-SOIL 21.7 26.8 8-8 130 Exposed 8-8-SOIL 50.8 62.0 8-9 130 Exposed 8-9-SOIL 67.8 81.9 7-1 134.45 Exposed 7-1-SOIL 27.7 32.0 7-2 134.45 Exposed 7-2-SOIL 9.00 12.0 7-3 134.45 Exposed 7-3-SOIL 33.9 38.7 7-4 134.45 Exposed 7-4-SOIL 46.2 50.0 6-1 135.39 Exposed 6-1-SOIL 120 142 6-2 135.39 Exposed 6-2-SOIL 127 149 5-1 139.81 Exposed 5-1-SOIL 98.9 121 5-2 139.81 Exposed 5-2-SOIL 62.7 80.3 4-1 140.18 Exposed 4-1-SOIL 22.7 26.7 4-2 140.18 Exposed 4-2-SOIL 24.9 29.6 B-1 145.433 Exposed B-1-SOIL 32.4 41.5 B-2 145.433 Exposed B-2-SOIL 24.1 29.5 C-1 145.455 Exposed C-1-SOIL 10.5 12.3 C-2 145.455 Exposed C-2-SOIL 36.4 42.7 A-1 147.423 Exposed A-1-SOIL 7.66 8.56 A-2 147.423 Exposed A-2-SOIL 21.1 22.3 1-1 155 Exposed 1-1-SOIL 100 120 1-2 155 Exposed 1-2-SOIL 75.1 93.1

FINAL


Figure 4.4.1 Scatterplot of Phase II soil Hg concentrations (dw) versus location Vegetation Analysis

Results of the vegetation sampling are shown in Table 4.4.2. Results are first listed for Reference Sites

and then for Exposed Sites. As with the Phase I analysis, results are listed both in terms of wet and dry

weights. Approximate location along the road (i.e., Road Km) is also indicated. Summary statistics are

provided in Table 4.4.3 and results of the mercury analysis are plotted in Figure 4.4.2. Overall, the mean

concentrations of mercury in vegetation sampled at both Reference and Exposed locations are similar to

the reported background levels of mercury in vegetation (Section 1.2.3) of 6-140 ppb ww (30-700 ppb dw)

listed by Adriano (1986).

0

2000

4000

6000

8000

10000

12000

110120130140150160

Road (Km)

Soil

Hg

(ppb

)

Reference Sites

Exposed SitesUSEPA soil limit=10000ppb

MYSRL Remediation Goal=1000ppb


Spill Area

Soil Benchmark for Plants= 10000 ppb

FINAL


Table 4.4.2 Results of Vegetation Analyses from the Phase II Sampling

Sample Road Site English Spanish Veg. Dry Total Hg (ppb) ID Km type Scientific name Common name Common

name Tissue1 Type Fraction wet wt dry wt

1-3 Indhum 155.00 Reference Indigofera humilis Indigo Forb 0.292 4.41 15.1 1-3 Vigsp 155.00 Reference Viguiera sp. Desert sunflower Suncho Shrub 0.258 5.24 20.3

1-3-Baclat 155.00 Reference Baccharis latifolia Groundsel Chilca negra Forb 0.352 6.35 18.0 5-4 Lansp 139.81 Reference Lantana sp. Lantana Shrub 0.404 7.92 19.6 5-4 Passp 139.81 Reference Paspalum sp. Paspalum Nudillo Grass 0.374 2.96 7.91

6-3 Zeamay 135.39 Reference Zea mays Corn Maiz Grass 0.129 1.14 8.82 6-4 Acamac 135.39 Reference Acacia macracantha Porknut Huarango Tree 0.487 8.47 17.4 6-4 Altpor 135.39 Reference Alternanthera porrigens Joyweed Moradillo Shrub 0.377 3.88 10.3 6-4 Crosp 135.39 Reference Croton sp. Croton Shrub 0.305 4.98 16.3

6-4 Schmol 135.39 Reference Schinus molle California pepper tree Molle Tree 0.418 7.39 17.7 14-4 Asccur 123.89 Reference Asclepias curassivaca Scarlet milkweed Flor de seda Forb 0.230 3.57 15.5 14-4 Cassp 123.89 Reference Cassia sp. Cinnamon Cinamomo Shrub 0.453 12.6 27.8

14-4 Riccom 123.89 Reference Ricinus communis Castor bean Higuerilla Tree 0.280 3.45 12.3 15-2 Baclan 119.73 Reference Bacchars lanceolata Groundsel Chilca Shrub 0.323 3.84 11.9 15-2 Bidpil 119.73 Reference Bidens pilosa Beggar's tick Cadillo Forb 0.198 1.65 8.33

15-2 Polsem 119.73 Reference Polypogon semiverticilatum Beard grass Grass 0.285 4.39 15.4 15-3 Capsp 119.73 Reference Capsicum sp. Cayenne pepper Aji verde fruit Forb 0.254 3.58 14.1

15-3-Arrxan 119.73 Reference Arracacia xanthorrihiga Peruvian carrot Arracacha Forb 0.154 24.0 156 15-3-Capfru 119.73 Reference Capsicum frutescens Cayenne pepper Aji verde fruit Forb 0.237 2.23 9.41

1-1 Pencla 155.00 Exposed Pennisetum clandestinum Kikuyu grass Kikuyu Grass 0.330 31.6 95.8 1-1 Sonole 155.00 Exposed Sonchus oleraceus Sow thistle Cerraja Forb 0.291 28.1 96.7 1-1 Trirep 155.00 Exposed Trifolium repens White clover Trebol Forb 0.449 49.5 110 1-2 Plasp 155.00 Exposed Plantago sp. Plantain Llanten macho Forb 0.320 56.3 176

1-2 Polsem 155.00 Exposed Polypogon semiverticilatum Beard grass Grass 0.476 54.8 115 A-1 Sonole 147.42 Exposed Sonchus oleraceus Sow thistle Cerraja Forb 0.182 3.63 19.6 A-1 Versp 147.42 Exposed Verbena sp. Verbena Verbena Forb 0.299 9.53 31.9

A-1-Melind 147.42 Exposed Melilotus Indica Clover Forb 0.267 4.00 15.0 A-2 Baclat 147.42 Exposed Baccharis latifolia Groundsel Chilca negra Forb 0.372 4.29 11.5 A-2 Calsp 147.42 Exposed Calceolaria sp. Pocket book plant Globito Forb 0.180 2.78 15.5 A-2-Dalsp 147.42 Exposed Dalea sp. Dalea Shrub 0.249 3.33 13.4 C-1 Bascp 145.46 Exposed Baccharis sp. Groundsel Chilca negra Forb 0.338 3.92 11.6 C-1 Calsp 145.46 Exposed Calceolaria sp. Pocket book plant Globito Forb 0.204 3.00 14.7

C-1 Escpen 145.46 Exposed Escallonia pendula Escallonia Pauco Tree 0.328 3.11 9.49 C-2 Spajun 145.46 Exposed Spartium junceum Spanish broom Retama Shrub 0.303 1.36 4.49 C-2-Hypsp 145.46 Exposed Hyptis sp. Mint weed Shrub 0.310 5.96 19.2 C-2-Minsp 145.46 Exposed Minthostachys sp. Mint Chancua Shrub 0.313 4.59 14.7

FINAL


Table 4.4.2 Results of Vegetation Analyses from the Phase II Sampling (continued)

Sample Road Site English Spanish Veg. Dry Total Hg (ppb) ID Km type Scientific name Common name Common name Tissue1 Type Fraction wet wt dry wt

B-1 Escpen 145.43 Exposed Escallonia pendula Escallonia Pauco Tree 0.277 2.19 7.90 B-1 Phesp 145.43 Exposed Phenaz sp. Phenax Fura parede Shrub 0.247 3.47 14.1 B-1-Rhysp 145.43 Exposed Rhynchosia sp. Snoutbean Shrub 0.360 2.16 6.00 B-2 Lansp 145.43 Exposed Lantana sp. Lantana Shrub 0.333 5.11 15.3 B-2-Baclat 145.43 Exposed Baccharis latifolia Groundsel Chilca negra Forb 0.321 7.72 24.1 B-2-Pencla 145.43 Exposed Pennisetum clandestinum Kikuyu grass Kikuyu Grass 0.251 3.78 15.1 4-1 Passp 140.18 Exposed Paspalum sp. Paspalum Nudillo Grass 0.438 19.7 45.0 4-2 Trirep 140.18 Exposed Trifolium repens White clover Trebol Forb 0.417 20.0 48.0 5-1 Pencla 139.81 Exposed Pennisetum clandestinum Kikuyu grass Kikuyu Grass 0.350 102 291 5-1 Plasp 139.81 Exposed Plantago sp. Plantain Llanten macho Forb 0.304 26.4 86.8

5-2 Cyndac 139.81 Exposed Cynodon dactylon Bermuda grass Grama dulce Grass 0.496 12.6 25.5 5-2 Pencla 139.81 Exposed Pennisetum clandestinum Kikuyu grass Kikuyu Grass 0.416 14.8 35.7 5-3 Cheamb 139.81 Exposed Chenopodium ambrosiodes Mexican tea Paico Forb 0.281 3.41 12.1 5-3 Phesp 139.81 Exposed Phenax sp. Phenax Fura parede Shrub 0.311 3.78 12.2 6-1 Brosp 135.39 Exposed Browalia sp. Bush violet Forb 0.391 5.51 14.1 6-1 Caespi 135.39 Exposed Caesalpinia spinosa Spiny holdback Taya Tree 0.482 5.09 10.6 6-1 Pencla 135.39 Exposed Pennisetum clandestinum Kikuyu grass Kikuyu Grass 0.350 5.39 15.4 6-2 Budsp 135.39 Exposed Buddleja sp. White stick Palo blanco Tree 0.324 2.82 8.70 6-2 Oxyvis 135.39 Exposed Oxybaphus viscosus Umbrella wort Forb 0.199 2.96 14.9 6-2 Penweb 135.39 Exposed Pennisetum weberbaueri Fox tail Rabo de zorro Grass 0.250 ND < 0.81 ND < 3.24 7-1 Corsp 134.45 Exposed Cortaderia sp. Pampas grass Grass 0.309 5.48 17.7

7-1 Phycan 134.45 Exposed Phyla canescens Lippia Turre hembra Forb 0.361 3.12 8.65 7-2 Dessp 134.45 Exposed Desmondium sp. Trefoil Forb 0.329 2.82 8.57 7-2 Ophchi 134.45 Exposed Ophryosporus chica Chilca Forb 0.237 2.54 10.7 7-2 Rhysp 134.45 Exposed Rhynchosia sp. Snoutbean Shrub 0.466 4.27 9.15

7-3 Cheamb 134.45 Exposed Chenopodium ambrosiodes Mexican tea Paico Forb 0.195 8.47 43.5 7-3 Plasp 134.45 Exposed Plantago sp. Plantain Llanten macho Forb 0.217 1.48 6.83

7-3 Sacoff-leaves 134.45 Exposed Saccharum officinarum Sugar cane Cana de azucar leaves Grass 0.349 ND < 0.81 ND < 2.39 7-3 Sacoff-stalk 134.45 Exposed Saccharum officinarum Sugar cane Cana de azucar stalk Grass 0.339 ND < 0 .81 ND < 2.39

7-3 Sidsp 134.45 Exposed Sida sp. Mallow Yendon Shrub 0.335 6.87 20.5 7-4 Setsp 134.45 Exposed Setaria sp. Foxtail Grass 0.388 9.09 23.4 7-4 Sposp 134.45 Exposed Sporobolus sp. Dropseed Pasto negro Grass 0.582 35.3 60.6

8-1 Annche 130.00 Exposed Annona cherimola Custard apple Cherimoya Tree 0.329 3.09 9.38 8-1 Minsp 130.00 Exposed Minthostachy sp. Mint Chancua Shrub 0.271 2.21 8.15 8-1 Phycan 130.00 Exposed Phyla canescens Lippia Turre hembra Forb 0.238 4.07 17.1 8-2 Altpor 130.00 Exposed Alternanthera porrigens Joyweed Moradilla Forb 0.227 2.72 12.0 8-2 Rosoff 130.00 Exposed Rosmarinus officinalis Rosemary Romero Shrub 0.500 10.9 21.8 8-2 Taroff 130.00 Exposed Taraxacum officinale Dandelion Diente de leon Forb 0.262 6.03 23.0

FINAL




8-3 Amacel 130.00 Exposed Amaranthus celosioides Amaranth Yuyo Forb 0.181 1.62 8.95 8-3 Crosp 130.00 Exposed Croton sp. Croton Shrub 0.389 5.03 12.9

8-3 Ophchi 130.00 Exposed Ophryosporus chilca Chilca Forb 0.376 3.15 8.38 8-4 Annche 130.00 Exposed Annona cherimola Custard apple Cherimoya Tree 0.303 4.43 14.6 8-4 Arudon 130.00 Exposed Arundo donax Gieant reed Carrizo Grass 0.564 13.2 23.4 8-4 Phesp 130.00 Exposed Phenax sp. Phenax Fura parede Shrub 0.199 2.91 14.6 8-5 Altpor 130.00 Exposed Alternanthera porrigens Joyweed Moradillo Shrub 0.310 2.67 8.61 8-5 Pencla 130.00 Exposed Pennisetum clandestinum Kikuyu grass Kikuyu Grass 0.333 2.77 8.32 8-5 Phyang 130.00 Exposed Physalis angulata Wild cherry Capuli cimarron Forb 0.130 1.37 10.5 8-6 Cesaur 130.00 Exposed Cestrum auriculatum Jasmine Heirba santa Shrub 0.291 5.22 17.9 8-6 Leonep 130.00 Exposed Leonotis nepetifolia Lion’s ear Ponchequiro Shrub 0.261 2.58 9.88 8-6 Pencla 130.00 Exposed Pennisetum clandestinum Kikuyu grass Kikuyu Grass 0.279 2.59 9.28 8-7 Brosp 130.00 Exposed Browalia sp. Bush violet Forb 0.269 4.11 15.3 8-7 Cesaur 130.00 Exposed Cestrum auriculatum Jasmine Heirba santa Shrub 0.292 4.67 16.0 8-7 Phesp 130.00 Exposed Phenax sp. Phenax Fura parede Shrub 0.197 2.78 14.1

8-9 Annche 130.00 Exposed Annona cherimola Custard apple Cherimoya Tree 0.317 3.96 12.5 8-9 Cessp 130.00 Exposed Cestrum sp. Jasmine Heirba santa Shrub 0.227 3.08 13.6

8-9 Ophchi 130.00 Exposed Ophryosporus chilca Chilca Forb 0.231 2.54 11.0 10-1 Pencla 128.94 Exposed Pennisetum clandestinum Kikuyu grass Kikuyu Grass 0.338 4.59 13.6 10-1 Phycan 128.94 Exposed Phyla cannescens Lippia Turre hembra Forb 0.302 3.34 11.1 10-2 Annche 128.94 Exposed Annona cherimola Custard apple Cherimoya Tree 0.395 7.03 17.8 10-2 Asccur 128.94 Exposed Asclepias curassavica Scarlet milkweed Flor de seda Forb 0.203 1.67 8.23 10-3 Baclan 128.94 Exposed Baccharis lanceolata Groundsel Chilco Shrub 0.418 6.18 14.8 10-3 Minsp 128.94 Exposed Minthostachys sp. Mint Chancua Shrub 0.270 2.67 9.89 10-3 Ophchi 128.94 Exposed Ophryisporus chilca Chilca Forb 0.307 2.56 8.34 13-1 Annche 124.77 Exposed Annona cherimola Custard apple Cherimoya Tree 0.336 5.65 16.8 13-1 Cyndoc 124.77 Exposed Cynodon dactylon Bermuda grass Grama dulce Grass 0.446 4.01 8.99 13-1-Leanep 124.77 Exposed Leonotis nepetifolia Lion’s ear Ponchequiro Shrub 0.252 3.23 12.8 13-2 Acamac 124.77 Exposed Acacia macracantha Porknut Huarango Tree 0.453 8.10 17.9 13-2 Altpor 124.7 7 Exposed Alternanthera porrigens Joyweed Moradillo Shrub 0.381 4.23 11.1 13-2 Cesaur 124.77 Exposed Cestrum auriculatum Jasmine Heirba santa Shrub 0.283 4.07 14.4 13-2 Crosp 124.77 Exposed Croton sp. Croton Shrub 0.427 8.94 20.9

13-3 Annche 124.77 Exposed Annona cherimola Custard apple Cherimoya Tree 0.350 3.38 9.65 13-3 Citlim-fruits 124.77 Exposed Citrus limon Lemon Limon fruit Tree 0.167 0.21 1.28 13-3 Citlim-leaves 124.77 Exposed Citrus limon Lemon Limon leaves Tree 0.447 10.1 22.6

13-4 Asccur 124.77 Exposed Asclepias curassavica Scarlet milkweed Flor de seda Forb 0.203 2.51 12.4 13-4 Cucdip 124.77 Exposed Cucumis dipsaceus Hedgehog Jaboncillo de campo Forb 0.242 3.03 12.5 13-4 Leonep 124.77 Exposed Leonotis nepetifolia Lion’s ear Ponchequiro Shrub 0.213 2.27 10.7

FINAL




13-5 Brasp 124.77 Exposed Brassica sp. Mustard Forb 0.242 1.75 7.23 13-5 Helsp 124.77 Exposed Heliotropium sp. Heliotrope Forb 0.255 3.61 14.2

14-1 Phycan 123.89 Exposed Phyla canescens Lippia Turre hembra Forb 0.350 3.78 10.8 14-1 Riccom 123.89 Exposed Ricinus communis Castor bean Higuerilla Tree 0.220 2.04 9.29 14-1 Solnig 123.89 Exposed Solanum nigrum Black nightshade Huerba mora Forb 0.249 3.23 13.0 14-2 Amasp 123.89 Exposed Amaranthus sp. Amaranth Yuyo Forb 0.313 7.32 23.4 14-2 Bidpil 123.89 Exposed Bidens pilosa Beggar's tick Cadillo Forb 0.200 3.01 15.1 14-2 Oensp 123.89 Exposed Oenothera sp. Evening primrose Flor de cavo Forb 0.430 7.39 17.2

14-3 Ammvis 123.89 Exposed Ammi visnaga Toothpick plant Visnaga Forb 0.149 1.30 8.72 14-3 Asccur 123.89 Exposed Asclepias curassivaca Scarlet milkweed Flor de seda Forb 0.181 1.72 9.50 14-3 Cyndac 123.89 Exposed Cynodon dactylon Bermuda grass Grama dulce Grass 0.536 4.90 9.14 14-3 Datstr 123.89 Exposed Datura stoamonium Jimson weed Chamico Forb 0.163 1.85 11.3 14-3 Galcil 123.89 Exposed Galisonga ciliata Hairy galinsoga Galinsoga Forb 0.192 1.97 10.3 14-3 Staarv 123.89 Exposed Stachys arvensis Field Woundwort Supiquehua Forb 0.284 14.0 49.3

14-3 Zeamay-leaves 123.89 Exposed Zea mays Corn Maiz leaves Grass 0.242 0.60 2.47 14-3 Zeamay-stalk 123.89 Exposed Zea mays Corn Maiz stalk Grass 0.166 0.11 0.69

15-1 Crosp 119.73 Exposed Croton sp. Croton Shrub 0.401 9.08 22.6 15-1 Solsp 119.73 Exposed Solanum sp. Nightshade Huerba mora Forb 0.268 5.28 19.7

1 aboveground tissue collected unless specific tissue-type noted ND= non detect (below the laboratory detection limit)

FINAL


Figure 4.4.2 Total Hg tissue concentrations (ww) in Phase II vegetation collected at

reference and exposed locations. Wet weight and dry weight values are plotted separately.

0

20

40

60

80

100

120

115125135145155

Location (Road Km)

Tot

al H

g (p

pb, w

w)

Reference samples

Exposed samples


Spill Area

Human Dietary Benchmark= 1600 ppb

0

50

100

150

200

250

300

350

115125135145155

Location (Road Km)

Tot

al H

g (p

pb, d

w)

Reference samples

Exposed samples


Spill Area

Bird Dietary Benchmark= 4000 Mammal Dietary Benchmark= 2000

FINAL


Table 4.4.3 Summary Statistics for the Phase II Vegetation Sampling

mean 95%UCL range (ppb) (ppb) (ppb)


Exposed wet weight 7.7 9.8 0.11-102 dry weight 22.8 28.4 0.69-291

Terrestrial Insect Analysis

Results of the insect tissue sampling are shown in Table 4.4.4. Results are listed by location along the road

and by the type of sample (Reference or Exposed). A scatterplot of the measured insect concentrations

versus location along the road is shown in Figure 4.4.3. Summary statistics are provided in Table 4.4.5.

The mean and 95 % UCL of the mean insect tissue concentrations from the Exposed locations were less

than Reference locations, though overall, the measured insect tissue concentrations at all of the Exposed

and Reference Sites were low and are indicative of background levels in the environment.

FINAL


Table 4.4.4 Results of the Phase II Terrestrial Insect Samples Collected in 2002

Total Hg, ng/g Sample ID Road Km Site type

Dry Fraction wet wt basis dry wt basis

1-3 Insects 155 Reference 0.39 43.3 110 5-4 Insects 139.81 Reference 0.31 2.43 7.87 6-3 Insects 135.39 Reference 0.43 6.76 15.9 6-4 Insects 135.39 Reference 0.48 6.14 12.7

13-6 Insects 124.77 Reference 0.42 1.77 4.25 14-4 Insects 123.89 Reference NA 7.93 - 15-2 Insects 119.73 Reference 0.39 17.9 45.9 15-3 Insects 119.73 Reference 0.41 3.55 8.60

1-1 Insects 155 Exposed 0.36 13.4 36.8 1-2 Insects 155 Exposed NA 25.4 - A-1 Insects 147.423 Exposed 0.37 9.53 25.7 A-2 Insects 147.423 Exposed 0.31 7.66 24.6 C-1 Insects 145.465 Exposed 0.42 11.7 28.1 C-2 Insects 145.465 Exposed 0.34 7.47 21.9 B-1 Insects 145.433 Exposed 0.30 7.92 26.3 B-2 Insects 145.433 Exposed 0.30 10.1 33.6 4-1 Insects 140.18 Exposed 0.30 3.68 12.2 4-2 Insects 140.18 Exposed 0.36 8.51 23.5 5-1 Insects 139.81 Exposed 0.46 2.81 6.12 5-2 Insects 139.18 Exposed 0.32 2.48 7.80 5-3 Insects 139.81 Exposed 0.40 4.93 12.2 6-1 Insectsa 135.39 Exposed 0.95 5.23 5.51 6-2 Insects 135.39 Exposed 0.55 73.4 134 7-1 Insects 134.45 Exposed 0.51 16.9 32.8 7-2 Insects 134.45 Exposed NA 14.5 - 7-3 Insects 134.45 Exposed 0.55 3.71 6.77 7-4 Insects 134.45 Exposed 0.42 3.74 8.98 8-1 Insects 130 Exposed 0.43 12.9 30.1 8-2 Insects 130 Exposed 0.64 42.1 66.2 8-3 Insects 130 Exposed 0.35 3.26 9.31 8-4 Insects 130 Exposed 0.36 2.71 7.60 8-5 Insects 130 Exposed 0.33 2.36 7.19 8-6 Insects 130 Exposed 0.35 8.79 25.1 8-7 Insects 130 Exposed 0.42 6.46 15.2 8-9 Insects 130 Exposed 0.31 4.3 14.1

10-1 Insects 128.94 Exposed 0.35 2.00 5.79 10-2 Insects 128.94 Exposed 0.34 1.38 4.11 10-3 Insects 128.94 Exposed 0.40 1.52 3.81 13-1 Insects 124.77 Exposed 0.38 15.2 39.8 13-2 Insects 124.77 Exposed 0.34 7.35 21.9 13-3 Insects 124.77 Exposed 0.38 10.9 28.5 13-4 Insects 124.77 Exposed 0.34 3.36 9.77 13-5 Insects 124.77 Exposed 0.31 1.58 5.08 14-1 Insects 123.89 Exposed 0.36 3.44 9.61 14-2 Insects 123.89 Exposed 0.33 2.74 8.26 14-3 Insects 123.89 Exposed 0.36 10.5 29.1 15-1 Insects 119.73 Exposed 0.27 3.28 12.0 aSample is reported as an estimate due to laboratory error (spilt sample) NA= not analyzed due to insufficient sample mass

FINAL


Figure 4.4.3 Scatterplot of mercury concentrations in insects versus location (Phase II). Wet

weight and dry weight values are plotted separately.

0

10

20

30

40

50

60

70

80

110120130140150160

Location (Road Km)

Inse

ct H

g (p

pb, w

w)

Reference sites

Exposed sites

Spill Area

Insect Tissue Benchmark=150 ppb

0

20

40

60

80

100

120

140

160

110120130140150160

Location (Road Km)

Inse

ct H

g (p

pb, d

w)

Reference sitesExposed sites

Spill Area




FINAL


Table 4.4.5 Summary Statistics for the Phase II Insect Sampling

mean 95%UCL range (ppb, ww) (ppb, ww) (ppb, ww)


Exposed wet weight 9.7 13.2 1.38-7.34 dry weight 21.6 28.0 3.81-134

4.4.2 Sampling and Tissue Analysis of Aquatic Biota

The Phase II fish and aquatic macroinvertebrate samples were collected by ENKON Environmental

(Surrey, British Columbia) in September of 2001. Sampling methodology, photographs, and information on

habitat conditions at each site are included in Appendix F. Most of the locations sampled in Phase I were

re-sampled in Phase II. The Site 2-1 and 2-2 sampling locations were not re-sampled in Phase II because

they were determined to be duplicative of the data collected at Site 2-3. Additionally, fish sampling was

not conducted at Sites 5-2, 5-3, or 6-1 since no fish were present at these locations during the Phase I

sampling. All of the Phase I and II sampling locations are shown on Map 3. While the Phase I sampling

was conducted prior to the wet season and therefore prior to possible movement of mercury into the

waterways, the Phase II sampling was conducted after the first wet season and therefore after the

potential migration of mercury into the waterways.

Aquatic Macroinvertebrate Analysis

Tissue concentrations for the composite macroinvertebrate samples (i.e., all species together) and

individual freshwater crabs are shown in Table 4.4.6. Both total and methylmercury concentrations are

shown on both a dry weight and wet weight basis, as available. The higher of the methyl or total mercury

values are plotted in Figure 4.4.4. The percent of the total mercury present in the form of methylmercury

in the macroinvertebrate samples ranged from 30 to 100% (Table 4.4.6). Values of greater than 100%

reflect differences in the analytical methodology used to analyze for total versus methylmercury (Appendix

G).

FINAL


Table 4.4.6 Mercury Concentration in Phase II Aquatic Macroinvertebrate Samples

Sample

Road

Location

Dry

Total Hg (ppb)

Methyl Hg (ppb)

methyl/

Sample ID Type1 Zone Site Km Type Fraction ww dw ww dw total

Crab (4.7 cm) whole Crab-whole 1 Reservoir 50 Reservoir 0.401 58.6 146 71.2 178 1.21 Crab (7.7 cm) whole Crab-whole 1 Reservoir 50 Reservoir 0.408 77.8 191 90.6 222 1.16 Crab (8.8 cm) whole Crab-whole 1 Reservoir 50 Reservoir 0.412 154 373 104 254 0.68 Crab (5.7 cm) whole Crab-whole 1 Reservoir 50 Reservoir 0.455 80.8 178 91.3 201 1.13

Z1S1-B Composite 1 1 52 Downstream 0.282 18.2 64.4 13.4 47.7 0.74 Z1S1-B(split) Composite 1 1 52 Downstream 0.145 11.0 76.2 8.97 61.8 0.81

Z2S3-B Composite 2 3 94 Downstream 0.207 11.1 53.6 9.31 45.0 0.84 Crab - whole Crab-whole 2 3 94 Downstream 0.460 77.1 168 73.6 160 0.95

Z3S1-B Composite 3 1 115 Exposed 0.263 13.3 50.7 9.93 37.8 0.75 Z3S2-B Composite 3 2 126 Exposed 0.242 28.0 116 22.3 92.3 0.80 Z3S3-B

(non-megaloptera) Composite 3 3 132 Exposed 0.258 17.1 66.1 8.85 34.3 0.52

Z3S3-B (megaloptera spp.)

Composite 3 3 132 Exposed 0.234 15.2 65.0 8.61 36.8 0.57

Z4S1-B Composite 4 1 134 Exposed 0.195 7.84 40.2 5.77 29.6 0.74 Z5S1-B Composite 5 1 133 Exposed 0.201 21.4 106 16.5 81.9 0.77 Z5S2-B Composite 5 2 153 Exposed 0.246 31.1 126 17.9 72.9 0.58 Z5S3-B Composite 5 3 155 Exposed 0.172 32.0 186 9.54 55.4 0.30 Z6S1-B Composite 6 1 157 Reference 0.260 130 501 77.1 296 0.59 Z7S1-B Composite 7 1 165* Reference 0.196 8.82 45.0 6.22 31.8 0.71

1Composite= the analyzed sample is a composite of all of the macroinvertebrates collected at that site * Zone 7 Site 1 is located in an upstream tributary (Rio Huacraruca) of the Jequetepeque

The tissue concentrations measured at locations within the spill area are compared to upstream,

downstream, and all of the non-spill sampling locations in Table 4.4.7. There is no indication that the

mercury concentration in invertebrate tissues within the spill area, or downstream of the spill area, are

elevated as a result of the spilt mercury. Overall, mercury concentrations in the Phase II

macroinvertebrate samples generally were low and within typical background concentrations in the

environment (Table 1.2.2).

Table 4.4.7 Comparison of Mercury Tissue Concentrations (Phase II) in Macroinvertebrates at Different Sample Locations

No. Mean (ppb) 95% UCL (ppb) Range (ppb) Area samples ww dw ww dw ww dw Spill Area 8 20.7 94.5 26.7 127 7.84-32.0 40.2-186 Upstream (Reference) 2 69.6 273.0 453.1 1712 8.82-130 45-501 Downstream 8 65.5 166.9 98.9 237.8 11.0-154 53.6-373 All non-spill 10 66.4 188.1 96.8 274.9 8.82-154 45-501 All samples 18 46.1 146.5 64.6 196.8 7.84-154 40.2-501

FINAL


Figure 4.4.4 Mercury concentration in macroinvertebrates versus sampling location (Phase

II). Wet weight and dry weight values are plotted separately.

0

100

200

300

400

500

600

456585105125145165

Location (Road Km)

Hg

(ppb

, dw

)

Individual crabsComposite samples

Spill Area


Bird Methylmercury Dietary Benchmark= 2500 ppb

0

20

40

60

80

100

120

140

160

180

456585105125145165

Location (Road Km)

Hg

(ppb

, ww

)

Individual crabsComposite samples


Spill Area

Macroinvertebrate Tissue Benchmark= 150 ppb

Human Dietary (MeHg) Benchmark= 300

FINAL


Fish tissue analysis

All of the Phase II fish tissue analysis data are shown in Table 4.4.8. Fish were collected at nine

locations- one upstream of the spill area, five within the spill area, and three downstream of the spill area.

The results of the Phase I analysis of fish tissue indicated that essentially all of the mercury present in the

fish tissue was in the methylated form and that the analytical methodology used for the methylmercury

analysis tended to produce slightly higher mercury values (Appendix G). Due to these factors, all of the

Phase II samples were analyzed for methylmercury, with only a percentage of the samples also analyzed

for total mercury.

A total of 114 different fish tissues were analyzed. Of the 114 analyses, 11 were of head tissue, 45 of

muscle tissue, 46 of total fish, and 12 of muscle+head tissue. The muscle+head tissue samples were a

result of an error at Frontier Geosciences, but still provide useful information and are included in

subsequent evaluations and discussions. For the samples that were analyzed for both methyl and total

mercury, the percent of mercury present in the methyl form ranged from 89% to 100%. To be

conservative, we have assumed that all of the mercury in fish is present in the methyl form and have

utilized the highest recorded mercury level (either the total or the methyl) for each sample in the risk

calculations and evaluations. Four of the samples analyzed had mercury concentrations that were higher

than the maximum value recorded in the Phase I sampling of 605 ppb (ww). These four samples are all

from the Gallito Ciego Reservoir. Frontier Geosciences was asked to re-analyze these samples. The

sample IDs and results of the two analyses are shown in Table 4.4.9. For three of the four samples, a

new digest was made prior to the re-analysis. For the fourth sample, there was insufficient material for a

re-digest, so this sample was only re-analyzed. The higher value from the two analyses is utilized in the

risk calculations and evaluations.

FINAL


Table 4.4.8 Results of Fish Analyses from the Phase II Sampling

Sample Length Tissue Dry Total Hg (ppb) Methyl Hg (ppb) methyl/ Road Identification Species (cm) Type Zone Site Fraction ww dw ww dw total Km Notes

Cachuela (10.3 cm) Cachuela 10.3 muscle 1 Reservoir 0.213 - - 242 1140 50 Reservoir Cascafe (21 cm) Cascafe 21 muscle 1 Reservoir 0.208 - - 138 664 50 Reservoir

Cascafe (23.2 cm) Cascafe 23.2 muscle 1 Reservoir 0.189 - - 183 970 50 Reservoir Cascafe (26 cm) Cascafe 26 muscle 1 Reservoir 0.194 159 822 170 876 1.06641 50 Reservoir

Cascafe (26.5 cm) Cascafe 26.5 head 1 Reservoir 0.188 - - 140 745 50 Reservoir Cascafe (26.5 cm) Cascafe 26.5 muscle 1 Reservoir 0.188 - - 235 1250 50 Reservoir

Charcoca (10.2 cm) Charcoca 10.2 muscle 1 Reservoir 0.229 - - 68.2 298 50 Reservoir Charcoca (10.5 cm) Charcoca 10.5 muscle 1 Reservoir 0.252 154 610 138 547 0.89636 50 Reservoir Charcoca (10.8 cm) Charcoca 10.8 muscle 1 Reservoir 0.212 - - 261 1230 50 Reservoir Charcoca (8.2 cm) Charcoca 8.2 whole 1 Reservoir 0.271 - - 104 385 50 Reservoir Charcoca (8.7 cm) Charcoca 8.7 whole 1 Reservoir 0.263 - - 61.0 232 50 Reservoir Charcoca (9.5 cm) Charcoca 9.5 whole 1 Reservoir 0.253 - - 147 579 50 Reservoir Charcoca (9.9 cm) Charcoca 9.9 whole 1 Reservoir 0.323 - - 80.9 250 50 Reservoir

Life ( 15.2 cm) Life 15.2 muscle/head 1 Reservoir 0.301 232 770 218 723 0.93938 50 Reservoir Life (12.6 cm) Life 12.6 muscle 1 Reservoir 0.245 - - 16.9 69.0 50 Reservoir Life (16.6 cm) Life 16.6 muscle 1 Reservoir 0.251 - - 159 633 50 Reservoir Life (16.8 cm) Life 16.8 head 1 Reservoir 0.241 - - 148 615 50 Reservoir Life (16.8 cm) Life 16.8 muscle 1 Reservoir 0.241 - - 362 1500 50 Reservoir

Mojarra (13 cm) Mojarra 13 muscle/head 1 Reservoir 0.307 - - 85.4 278 50 Reservoir Mojarra (13.5 cm) Mojarra 13.5 muscle 1 Reservoir 0.216 - - 79.3 367 50 Reservoir Mojarra (17.3 cm) Mojarra 17.3 head 1 Reservoir 0.189 - - 78.2 414 50 Reservoir Mojarra (17.3 cm) Mojarra 17.3 muscle 1 Reservoir 0.189 - - 116 614 50 Reservoir Mojarra (18.5 cm) Mojarra 18.5 muscle 1 Reservoir 0.178 88.4 497 78.9 443 0.89212 50 Reservoir

Nato (10.8 cm) Nato 10.8 muscle 1 Reservoir 0.163 - - 819 5020 50 Reservoir Nato (10.8 cm) * Nato 10.8 muscle 1 Reservoir 0.163 - - 357 2190 50 Reservoir

Nato (13 cm) Nato 13 muscle 1 Reservoir 0.186 - - 535 2870 50 Reservoir Nato (9.6 cm) Nato 9.6 whole 1 Reservoir 0.226 - - 392 1730 50 Reservoir Nato (9.7 cm) Nato 9.7 whole 1 Reservoir 0.228 - - 341 1490 50 Reservoir

Nato A (10.2 cm) Nato 10.2 muscle 1 Reservoir - - - 1410 - 50 Reservoir Nato A (10.2 cm) ** Nato 10.2 muscle 1 Reservoir NA - - 1430 - 50 Reservoir

Nato A (9.2 cm) Nato 9.2 whole 1 Reservoir 0.248 - - 301 1220 50 Reservoir Nato B (10.2 cm) Nato 10.2 muscle 1 Reservoir 0.210 543 - 684 3260 1.26011 50 Reservoir

Nato B (10.2 cm) * Nato 10.2 muscle 1 Reservoir 0.210 - - 722 3440 50 Reservoir Nato B (9.2 cm) Nato 9.2 whole 1 Reservoir 0.221 - - 401 1810 50 Reservoir

FINAL


Table 4.4.8 Results of Fish Analyses from the Phase II Sampling (continued)


Pejerrey (20.6 cm) Pejerrey 20.6 muscle 1 Reservoir 0.211 - - 51.3 243 50 Reservoir Pejerrey (21 cm) Pejerrey 21 head 1 Reservoir 0.212 55.8 263 51.7 244 0.92784 50 Reservoir Pejerrey (21 cm) Pejerrey 21 muscle 1 Reservoir 0.212 73.5 347 68.3 322 0.92932 50 Reservoir

Pejerrey (24.3 cm) Pejerrey 24.3 muscle/head 1 Reservoir 0.247 - - 157 636 50 Reservoir Pejerrey (25 cm) Pejerrey 25 muscle/head 1 Reservoir 0.240 - - 64.2 267 50 Reservoir Picalon (11.7 cm) Picalon 11.7 muscle/head 1 Reservoir 0.260 - - 708 2720 50 Reservoir

Picalon (11.7 cm) * Picalon 11.7 muscle/head 1 Reservoir 0.260 - - 757 2910 50 Reservoir Tilapia (30 cm) Tilapia 30 muscle/head 1 Reservoir 0.259 32.1 124 31.9 123 0.99376 50 Reservoir

Tilapia (31.5 cm) Tilapia 31.5 head 1 Reservoir 0.181 - - 17.4 96.3 50 Reservoir Tilapia (31.5 cm) Tilapia 31.5 muscle 1 Reservoir 0.181 - - 50.5 279 50 Reservoir Cascafe (13.2 cm) Cascafe 13.2 muscle 1 1 0.220 63.4 288 76.9 350 1.21366 50 Downstream Cascafe (16.9 cm) Cascafe 16.9 head 1 1 0.209 - - 196 940 50 Downstream Cascafe (16.9 cm) Cascafe 16.9 muscle 1 1 0.209 - - 318 1520 50 Downstream

Charcoca (10.1 cm) Charcoca 10.1 muscle 1 1 0.234 - - 94.7 405 50 Downstream Charcoca (4.7 cm) Charcoca 4.7 whole 1 1 0.252 - - 22.4 89.0 50 Downstream Charcoca (6.2 cm) Charcoca 6.2 whole 1 1 0.273 24.8 90.7 27.1 99.2 1.09426 50 Downstream Charcoca (7.2 cm) Charcoca 7.2 whole 1 1 0.250 - - 88.0 352 50 Downstream Charcoca (7.7 cm) Charcoca 7.7 whole 1 1 0.248 - - 89.1 359 50 Downstream

Life (12 cm) Life 12 muscle/head 1 1 0.298 - - 36.5 122 50 Downstream Mojarra (12 cm) Mojarra 12 muscle 1 1 0.216 - - 113 524 50 Downstream

Mojarra (12.8 cm) Mojarra 12.8 muscle 1 1 0.204 - - 133 653 50 Downstream Mojarra (13.6 cm) Mojarra 13.6 head 1 1 0.197 66.4 337 87.1 442 1.31313 50 Downstream Mojarra (13.6 cm) Mojarra 13.6 muscle 1 1 0.197 117 592 109 556 0.93785 50 Downstream Mojarra (14.6 cm) Mojarra 14.6 muscle/head 1 1 0.272 - - 128 469 50 Downstream

Nato (6.4 cm) Nato 6.4 whole 1 1 0.257 - - 110 427 50 Downstream Charcoca (6 cm) Charcoca 6 whole 2 3 0.234 - - 16.4 70.0 94 Downstream

Charcoca (6.6 cm) Charcoca 6.6 whole 2 3 0.240 - - 32.8 137 94 Downstream Charcoca (8.7 cm) Charcoca 8.7 whole 2 3 0.246 55.9 227 68.9 280 1.23202 94 Downstream Charcoca (9 cm) Charcoca 9 whole 2 3 0.263 - - 22.9 87.1 94 Downstream

Mojarra (10.7 cm) Mojarra 10.7 muscle/head 2 3 0.330 - - 19.1 57.9 94 Downstream Charcoca (11 cm) Charcoca 11 muscle 3 1 0.237 41.0 173 42.5 179 1.0369 115 Exposed

Charcoca (11.9 cm) Charcoca 11.9 head 3 1 0.232 - - 60.3 260 115 Exposed Charcoca (11.9 cm) Charcoca 11.9 muscle 3 1 0.232 - - 104 448 115 Exposed Charcoca (9.5 cm) Charcoca 9.5 whole 3 1 0.289 - - 34.0 118 115 Exposed

FINAL




Charcoca A (10.7 cm) Charcoca 10.7 muscle 3 1 0.257 - - 42.9 167 115 Exposed Charcoca B (10.7 cm) Charcoca 10.7 muscle 3 1 0.223 - - 31.2 140 115 Exposed

Life (10 cm) Life 10 muscle 3 1 0.252 - - 35.0 139 115 Exposed Life (11.5 cm) Life 11.5 muscle 3 1 0.246 - - 27.3 111 115 Exposed Life (14.5 cm) Life 14.5 muscle 3 1 0.203 54.3 267 52.4 258 0.96553 115 Exposed Life (16 cm) Life 16 muscle 3 1 0.244 - - 60.4 247 115 Exposed

Nato (10.5 cm) Nato 10.5 head 3 1 0.227 - - 89.8 396 115 Exposed Nato (10.5 cm) Nato 10.5 muscle 3 1 0.227 - - 117 515 115 Exposed Nato (13.3 cm) Nato 13.3 muscle/head 3 1 0.267 - - 103 388 115 Exposed

Nato (7 cm) Nato 7 whole 3 1 0.246 - - 35.6 145 115 Exposed Nato (7.3 cm) Nato 7.3 whole 3 1 0.269 - - 23.9 88.8 115 Exposed Nato (7.7 cm) Nato 7.7 whole 3 1 0.237 - - 20.1 85.0 115 Exposed Nato (9.2 cm) Nato 9.2 whole 3 1 0.257 65.4 254 82.0 319 1.25464 115 Exposed Nato (9.8 cm) Nato 9.8 whole 3 1 0.249 - - 38.6 155 115 Exposed

Cachuela (10.4 cm) Cachuela 10.4 muscle 3 2 0.226 345 1530 441 1950 1.2775 126 Exposed Cachuela (10.5 cm) Cachuela 10.5 muscle 3 2 0.222 - - 323 1460 126 Exposed Chacoca (11.1 cm) Charcoca 11.1 head 3 2 0.266 - - 92.0 346 126 Exposed Chacoca (11.1 cm) Charcoca 11.1 muscle 3 2 0.266 - - 153 574 126 Exposed Charcoca (11 cm) Charcoca 11 muscle 3 2 0.244 - - 129 530 126 Exposed

Charcoca (12.2 cm) Charcoca 12.2 muscle/head 3 2 0.290 - - 164 565 126 Exposed Charcoca (9.9 cm) Charcoca 9.9 whole 3 2 0.245 - - 103 419 126 Exposed

Nato (10.6 cm) Nato 10.6 muscle 3 2 0.231 - - 120 519 126 Exposed Nato (10.8 cm) Nato 10.8 muscle 3 2 0.232 - - 73.6 317 126 Exposed Nato (11.7 cm) Nato 11.7 head 3 2 0.196 - - 131 668 126 Exposed Nato (11.7 cm) Nato 11.7 muscle 3 2 0.196 - - 189 967 126 Exposed Nato (12.4 cm) Nato 12.4 muscle 3 2 0.280 54.8 196 57.3 205 1.04613 126 Exposed Nato (7.8 cm) Nato 7.8 whole 3 2 0.248 - - 39.1 157 126 Exposed Nato (8.2 cm) Nato 8.2 whole 3 2 0.246 - - 38.8 158 126 Exposed

Nato A (7.9 cm) Nato 7.9 whole 3 2 0.272 97.3 358 99.6 366 1.02354 126 Exposed Nato B (7.9 cm) Nato 7.9 whole 3 2 0.232 - - 40.9 176 126 Exposed

Charcoca (8.8 cm) Charcoca 8.8 whole 3 3 0.275 - - 27.3 99.3 132 Exposed Nato (4 cm) Nato 4 whole 3 3 - - - 12.0 - 132 Exposed

Nato (5.8 cm) Nato 5.8 whole 3 3 0.283 - - 29.1 103 132 Exposed Nato A (7 cm) Nato 7 whole 3 3 0.280 25.5 90.9 31.9 114 1.25372 132 Exposed

FINAL




Nato B (7 cm) Nato 7 whole 3 3 0.277 - - 29.5 106 132 Exposed Pejerrey (14.8 cm) Pejerrey 14.8 muscle/head 3 3 0.276 - - 59.7 216 132 Exposed

Nato (2.4 cm) Nato 2.4 whole 4 1 - - - 10.5 - 134 Exposed Nato (3.2 cm) Nato 3.2 whole 4 1 - - - 8.35 - 134 Exposed Nato (6.5 cm) Nato 6.5 whole 4 1 0.288 - - 18.2 63.2 134 Exposed

Nato A (7.6 cm) Nato 7.6 whole 4 1 0.255 - - 55.9 219 134 Exposed Nato B (7.6 cm) Nato 7.6 whole 4 1 0.260 - - 31.2 120 134 Exposed Pejerrey (17 cm) Pejerrey 17 muscle 4 1 0.253 20.0 79.1 18.1 71.6 0.90548 134 Exposed Nato (5.8 cm) Nato 5.8 whole 5 1 0.250 - - 77.6 311 133 Exposed Nato (5.9 cm) Nato 5.9 whole 5 1 0.291 - - 58.7 202 133 Exposed Nato (6.8 cm) Nato 6.8 whole 5 1 0.304 - - 55.4 182 133 Exposed Nato (9.2 cm) Nato 9.2 whole 5 1 0.229 69.6 304 67.2 293 0.96522 133 Exposed Nato (4.3 cm) Nato 4.3 whole 7 1 0.237 - - 16.1 67.9 165 Upstream Nato (4.4 cm) Nato 4.4 whole 7 1 - - - 14.5 - 165 Upstream Nato (7 cm) Nato 7 whole 7 1 0.226 - - 44.4 197 165 Upstream

Nato (7.3 cm) Nato 7.3 whole 7 1 0.284 20.0 70.4 23.7 83.4 1.18506 165 Upstream * re-digested and re-analyzed duplicate sample ** duplicate sample only re-analyzed since insufficient material to re-digest and re-analyze

FINAL


Table 4.4.9 Re-analyzed Fish Tissue Samples from the Phase II Sampling

Methyl Hg (ppb, ww) Sample ID Tissue

Analyses Re-analyses Nato A (10.2 cm) muscle 1410 1430* Nato (10.8 cm) muscle 819 357 Picalon (11.7 cm) muscle/head 708 757 Nato B 10.2 muscle 684 722

* Sample only re-analyzed since not sufficient material to re-digest and then re-analyze

Summary statistics for the Phase II fish tissue analysis is provided in Table 4.4.10, and the maximum

mercury value for each sample is plotted versus location in Figure 4.4.5.

Table 4.4.10 Summary Statistics for the Phase II Fish Sampling

No. Mean (ppb) 95% UCL (ppb) Range (ppb) Area

samples ww dw ww dw ww dw Spill Area 50 75.8 333.2 94.1 419.1 8.35-441 63.2-1950 Upstream (Reference) 4 24.7 116.0 40.9 234.5 14.5-44.4 67.9-197 Downstream 60 189.1 774.7 234.4 971.6 16.4-1430 57.9-5020 All non-spill 64 178.8 742.8 228.1 932.5 14.5-1430 57.9-5020 All samples 114 133.7 566.2 163.3 683.5 8.35-1430 57.9-5020

Summary statistics, on a wet weight basis, are provided in Table 4.4.11 for each sampling location.

Table 4.4.11 Mercury Concentration in Fish at Each Location (Phase II)

No. of Mean 95% UCL Range Site Location

Samples (ppb,ww) (ppb,ww) (ppb,ww) Reservoir Downstream 40 238.7 312.7 16.9-1430 Site 1-1 Downstream 15 109.1 142.2 22.4-318 Site 2-3 Downstream 5 32.0 52.5 16.4-68.9 Site 3-1 Exposed 18 55.7 68.2 20.1-117 Site 3-2 Exposed 16 137.2 184.5 38.8-441 Site 3-3 Exposed 6 32.6 44.3 12.0-59.7 Site 4-1 Exposed 6 24.0 38.5 8.35-55.9 Site 5-1 Exposed 4 65.3 77.3 55.4-77.6 Site 7-1 Upstream1 4 24.7 40.9 14.5-44.4

(1) Zone 7 Site 1 (7-1) is located in an upstream tributary (Rio Huacraruca)

FINAL


Figure 4.4.5 Mercury concentration (ww) in fish at all sampling locations (Phase II). The Spill

Area is indicated by the marked line. Samples shown as collected at Km 165 are from a reference tributary upstream of the spill area. Wet weight and dry weight values are plotted separately.

0

200

400

600

800

1000

1200

1400

1600

456585105125145165

Location (Road Km)

Spill Area

To CajamarcaTo Trujillo

Human Methyl Dietary Benchmark= 300 ppb

Fish Tissue Benchmark= 2000 ppb

0

1 0 0 0

2 0 0 0

3 0 0 0

4 0 0 0

5 0 0 0

6 0 0 0

456 58 51 0 51 2 51 4 51 6 5

L o c a t i o n ( R o a d K m )

Sp i l l A rea

T o C a j a m a r c a To Truj i l lo

Bird Methyl Dietary Benchmark= 2500 ppb

FINAL


In order to evaluate fish consumed by the local human population, small fish (<10 cm) were analyzed as

whole fish, whereas larger fish (>10 cm) were segregated into muscle and head samples prior to analysis.

Table 4.4.12 shows the mean, 95% UCL, and maximum mercury concentrations (ww) across all of the

samples for each of these tissue types.

Table 4.4.12 Mercury Concentrations for Each Fish Tissue Type (Phase II)

Tissue Mean 95%UCL Range type (ppb, ww) (ppb, ww) (ppb, ww)

Head 99.7 127.1 17.4-1096 Muscle 196.2 260.3 16.9-1430 Head+muscle 153.2 257.1 19.2-1838 Whole 75.5 98.9 8.35-401

ww= wet weight

Muscle tissue had the highest mercury concentrations and whole body analyses had the lowest mercury

concentrations. This may be due to smaller fish being selected for whole body tissue analysis versus

smaller fish for whole body analysis. Generally, larger and older fish will have higher mercury

concentrations than smaller and younger fish (USEPA 1999a). However, a regression analysis of the data

shown in Figure 4.4.6 again indicated no significant relationship (R2=0.003) between fish length and

mercury concentrations in tissue.

Figure 4.4.6 Mercury concentrations (ww) in each fish tissue type plotted versus fish length (Phase II). Samples from all locations are included.

0

200

400

600

800

1000

1200

1400

1600

0 5 10 15 20 25 30 35

Fish length (cm)

Hg

(ppb

)

Hg concentration in head

Hg concentration in muscle

Hg concentration in whole fish

FINAL


Table 4.4.13 shows the mean mercury concentrations in each tissue type (head, muscle, or whole fish) for

each of the analyzed fish species, across all sampling locations. There is a significant degree of variation

between the fish species. Much of this variation, however, may be due to the small number of samples

analyzed for each fish species. The mean mercury concentrations in the heads of the different species

range from 17.4 to 148 ppb (ww). Tilapia had the lowest mean concentration in heads and Life had the

highest. In muscle tissue, Nato was the species with the highest mean concentration at 451 ppb (ww) and

Pejerrey had the lowest at 48.3 ppb (ww). Whole body analyses were only conducted for Charcoca and

Nato. Additional discussion of the life history and feeding habitats of the different species is provided in

Section 2.2.

Table 4.4.13 Mean Mercury Concentrations for Each Fish Species and Tissue Type (Phase II)

Head Muscle Head+Muscle Whole Species Hg (ppb, ww) Hg (ppb, ww) Hg (ppb, ww) Hg (ppb, ww) Cachuela ND 335 (3) ND ND Cascafe 168 (2) 187 (6) ND ND

Charcoca 76.2 (2) 108.1 (10) 164 (1) 61.6 (15) Life 148 (1) 102.1 (7) 134.3 (2) ND

Mojarra 82.7 (2) 107.9 (6) 77.5 (3) ND Nato 110.4 (2) 451.4 (9) 103 (1) 82.3 (31)

Pejerrey 55.8 (1) 48.3 (3) 93.6 (3) ND Picalon ND ND 757 (1) ND Tilapia 17.4 (1) 50.5 (1) 32.1 (1) ND

ND= no data ww= wet weight Values in parentheses indicate number of samples used in calculating the mean

4.5 Mercury Transfer to Terrestrial Biota

The sampling conducted at the site provides actual mercury exposure measurements for the majority of

the exposure pathways shown in Figures 2.3.1 and 2.3.2. The exception is that there was only four

terrestrial animal tissue samples collected during the joint November 2000 sampling effort (Section 4.3).

In order to allow for the evaluation of mercury concentrations in animal tissues and to assess the risk

potential to animals that consume other animal tissue (e.g., humans), the scientific literature was reviewed

for information on the transfer of mercury from the diet to animals. Transfer factors are required to

model the expected tissue concentrations of mercury in terrestrial animals that results from mercury

concentrations in the diet. Typically, these transfer values are called bioaccumulation factors, or BAFs,

and are calculated by dividing the concentration of mercury in animal tissue by the concentration of

mercury in the diet:

BAF= mercury concentration in animal tissue (ppb) mercury concentration in diet (ppb)

FINAL


If the BAF is less than 1, mercury does not accumulate to a greater degree in animals than it occurs in the

diet.

Values listed in the literature for transfer of mercury from dietary items to terrestrial animal tissue are

shown in Table 4.5.1. Values for transfer of non-methylmercury (e.g., ionic mercury) to mammal tissue

are shown first, followed by methylmercury BAFs. The range of values for transfer of non-methyl

mercury is 0.003 to 13.52, with a mean of 1.68 and a median value of 0.41. Fifty percent of the reported

values are greater than the median, and 50% are less. Of the 39 values reported in the literature, 24

(>60%) of the BAF values are less than 1.0. In general, the highest BAF values are associated with the

lowest dietary concentration. This suggests that the transfer of mercury from the diet to tissue is not

linear, and that as dietary concentrations increase, the relative uptake into tissues declines. The BAF

values for transfer of methylmercury from the diet to mammal tissues ranges from 0.168 to 5. The mean

of the five values listed in Table 4.5.1 for methylmercury transfer is 1.74, and the median is 0.819. The

mean value of 1.74 for methylmercury uptake is similar to the mean value of 1.68 for the non-

methylmercury BAFs. All of the BAFs found in the literature for the transfer of mercury from the diet

into bird tissue are for methylmercury forms. These values range from 0.56 to 8.6, with a mean of 2.36

and a median of 1.29. The mean value for ionic mercury transfer to mammal tissue of 1.68 and the mean

of 2.36 for transfer of mercury to bird tissue were used to model mercury transfer to mammal and bird

tissue in the RA.

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Table 4.5.1 Mercury BAFs for Birds and Mammals

Species Notes Tissue Type ppm Diet*

ppm Tissues* BAF Reference

MAMMAL-DIET

Chamois (goat) Total Hg, dw vegetation Muscle (ww) 14.4 0.040 0.003 Gnamus et al. 2000 Roe Deer Total Hg, dw vegetation Muscle (ww) 14.4 0.0794 0.006 Gnamus et al. 2000 Roe Deer Total Hg, dw vegetation Muscle (ww) 0.58 0.0034 0.006 Gnamus et al. 2000 Chamois (goat) Total Hg, dw vegetation Liver (ww) 14.4 0.192 0.013 Gnamus et al. 2000 Roe Deer Total Hg, dw vegetation Liver (ww) 0.58 0.0137 0.024 Gnamus et al. 2000 Roe Deer Total Hg, dw vegetation Muscle (ww) 0.08 0.0028 0.035 Gnamus et al. 2000 Goat Hg+2 (HgCl 2) Omental fat (ww) 73.9 3.5 0.047 Pathak and Bhowmik 1998 Roe Deer Total Hg, dw vegetation Liver (ww) 14.4 0.845 0.059 Gnamus et al. 2000 Chamois (goat) Total Hg, dw vegetation Muscle (ww) 0.21 0.02 0.095 Gnamus et al. 2000 Goat Hg+2 (HgCl 2) Brain (ww) 73.9 7.25 0.098 Pathak and Bhowmik 1998 Mouse Hg+2 (HgCl 2) Internal organs 5 0.545 0.109 Schroeder and Mitchener 1975 Roe Deer Total Hg, dw vegetation Muscle (ww) 0.21 0.0262 0.125 Gnamus et al. 2000 Roe Deer Total Hg, dw vegetation Liver (ww) 0.08 0.0142 0.178 Gnamus et al. 2000 Goat Hg+2 (HgCl 2) Heart (ww) 73.9 19.5 0.264 Pathak and Bhowmik 1998 Roe Deer Total Hg, dw vegetation Kidney (ww) 0.58 0.155 0.267 Gnamus et al. 2000 Goat Hg+2 (HgCl 2) Lung (ww) 73.9 20.5 0.277 Pathak and Bhowmik 1998 Chamois (goat) Total Hg, dw vegetation Kidney (ww) 14.4 3.35 0.233 Gnamus et al. 2000 Wolf Total Hg, deer muscle ww Muscle (ww) 0.0262 0.00945 0.361 Gnamus et al. 2000 Chamois (goat) Total Hg, dw vegetation Liver (ww) 0.21 0.077 0.367 Gnamus et al. 2000 Goat Hg+2 (HgCl 2) Skeletal muscle (ww) 73.9 30.5 0.413 Pathak and Bhowmik 1998 Goat Hg+2 (HgCl 2) Mesenteric lymph nodes (ww) 73.9 41.62 0.563 Pathak and Bhowmik 1998 Goat Hg+2 (HgCl 2) Intestines (ww) 73.9 43.75 0.592 Pathak and Bhowmik 1998 Goat Hg+2 (HgCl 2) Spleen (ww) 73.9 49.75 0.673 Pathak and Bhowmik 1998 White-footed Mouse Total Hg; ww Kidney (ww) 1.54 1.16 0.75 Talmage and Walton 1993 Goat Hg+2 (HgCl 2) Liver (ww) 73.9 79.75 1.079 Pathak and Bhowmik 1998 Roe Deer Total Hg, dw vegetation Liver (ww) 0.21 0.237 1.13 Gnamus et al. 2000 Roe Deer Total Hg, dw vegetation Kidney (ww) 14.4 18.7 1.30 Gnamus et al. 2000 Goat Hg+2 (HgCl 2) Kidneys (ww) 73.9 106 1.434 Pathak and Bhowmik 1998 Lynx Total Hg, deer muscle ww Muscle (ww) 0.0262 0.0424 1.618 Gnamus et al. 2000 Lynx Total Hg Muscle 0.15 0.37 2.47 Hernandez et al. 1985 Roe Deer Total Hg, dw vegetation Kidney (ww) 0.08 0.204 2.55 Gnamus et al. 2000 Lynx Total Hg, hare muscle ww Muscle (ww) 0.13 0.37 2.85 Hernandez et al. 1985 Wolf Total Hg, deer muscle ww Muscle (ww) 0.0028 0.00833 2.975 Gnamus et al. 2000 Lynx Total Hg, rabbit muscle ww Muscle (ww) 0.1 0.37 3.7 Hernandez et al. 1985 Shorttail Shrew Total Hg Kidney (ww) 8.82 38.8 4.4 Talmage and Walton 1993 Lynx Total Hg Liver 0.17 0.76 4.47 Hernandez et al. 1985 Chamois (goat) Total Hg, dw vegetation Kidney (ww) 0.21 1.48 7.05 Gnamus et al. 2000 Lynx Total Hg, deer muscle ww Muscle (ww) 0.0028 0.0271 9.68 Gnamus et al. 2000 Roe Deer Total Hg, dw vegetation Kidney (ww) 0.21 2.84 13.52 Gnamus et al. 2000

Wolf MethylHg, deer muscle ww Muscle (ww) 0.0371 0.00625 0.168 Gnamus et al. 2000 Lynx MethylHg, deer muscle ww Muscle (ww) 0.0371 0.0177 0.477 Gnamus et al. 2000 Wolf Methyl Hg, deer muscle ww Muscle (ww) 0.0095 0.00782 0.819 Gnamus et al. 2000 Lynx Methyl Hg, deer muscle ww Muscle (ww) 0.0095 0.0214 2.241 Gnamus et al. 2000 Mouse Methylmercury organs 1 5 5 Schroeder and Mitchener 1975

BIRD-DIET

Chicken Methylmercury dicyandiamide Liver 18 10.0 0.56 Fimreite and Karstad 1971 Chicken Methylmercury dicyandiamide Liver 12 7.2 0.60 Fimreite and Karstad 1971 Chicken Methylmercury dicyandiamide Liver 6 3.9 0.65 Fimreite and Karstad 1971 Japanese quail-female Methylmercury Liver 8 6.6 0.83 Aagdal et al. 1978 Hooded merganser (duck) Crayfish ww, assumed MeHg Breast 7.1 12.31 1.74 Vermeer et al. 1973 Common merganser (duck) Perch ww, assumed MeHg Breast 2.7 6.79 2.51 Vermeer et al. 1973 Japanese quail- male Methylmercury Liver 8 27 3.38 Aagdal et al. 1978 Mallard Methylmercury Egg 0.5 4.3 8.6 Heinz 1974

* values listed in dry weight unless otherwise noted

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5.0 RISK CHARACTERIZATION The Risk Characterization step of the RA takes the information gathered in the Analysis phase, which

includes both the Effects Characterization (Section 3) and the Exposure Assessment (Section 4), and

incorporates the findings with the conceptual model of the fate and transport of mercury developed in the

Problem Formulation step (Section 2), to arrive at risk estimates. Risk is evaluated through the use of

Hazard Quotients (HQs). HQs are calculated by dividing the Exposure Concentration (EC) by

Benchmark Values (USEPA 1998). An HQ less than 1 indicates minimal risk. HQs greater than 1

indicate that there may be the possibility of risk. The ECs are the measured concentrations of mercury in

different media (water and soil) and plant and animal tissues (Section 4). In order to provide a

conservative estimate of exposure, the 95% UCL of the mean mercury concentration in samples of the

various tissues collected were used as the ECs in the calculation of the HQ values. For water, the mean

value was used because the calculated values included the detection limit for samples that were below

detection. Because of this, the mean value is actually greater than the maximum detected value at some

locations, and thus provides a conservative estimate of exposure. For terrestrial animal tissues, the ECs

were modeled using the BAF values discussed in Section 4.5 and the measured concentration of mercury

in the diet. The Benchmark Values used in the HQ calculations were established in Section 3 and are

summarized in Table 3.4.1.

5.1 Aquatic Resources Aquatic biota can be exposed to mercury from pathways that originate from dissolved mercury in the

surface water column, or from mercury contained in sediment (Figure 2.3.2). Fish and macroinvertebrates

can uptake mercury directly from water. Macro-invertebrates can also be exposed to mercury from the

sediments, as can fish species that eat detritus on top of the sediments. Fish are the highest trophic

receptor in the aquatic systems, integrating mercury exposure from water as well as from ingestion of

plants and macroinvertebrates. Due to their position at the top of the food web in the aquatic systems, fish

are expected to have the highest mercury concentrations of the different types of aquatic biota.

Due to the rapid remediation effort and the recovery of the majority of the spilt mercury prior to the onset

of the wet season, it is unlikely that any significant amount of the spilt mercury entered the waterways.

This is supported by the data collected at the site. As discussed in Section 4.1, water and sediment

concentrations from Exposed and Reference locations are quite similar, and there is no evidence of

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increasing mercury concentrations between sampling events conducted in 2000 through 2002. The mean

concentration in water across all of the Exposed locations, over all sampling dates, is 0.017 ppb. The

mean concentration across all of the Reference locations, over all sampling dates, is also 0.017 ppb.

Because the detection limit was used in calculating both of these calculated means, these concentrations

are higher than the actual mean concentrations since some samples were below the detection limit. The

mean sediment mercury concentration across all of the Exposed sample locations, over all of the sampling

dates, is 112.4 ppb (dw). The corresponding mean for the Reference locations is 177.9 ppb (dw).

The calculated HQ values for macroinvertebrates and fish are shown in Table 5.1.1. Risk to aquatic biota

is evaluated from exposure to mercury in water and from tissue levels of mercury in fish and

macroinvertebrates.

Table 5.1.1 Calculated Hazard Quotients (HQs) for Aquatic Resources

FISH MACROINVERTEBRATES EC1 Benchmark EC1 Benchmark

ppb (ww) ppb (ww) HQ ppb (ww) ppb (ww) HQ

WATER Reference 0.017 0.2 0.09 0.017 0.2 0.09 Exposed 0.017 0.2 0.09 0.017 0.2 0.09

TISSUE Phase I Upstream (Reference) 61.3 2000 0.03 151.3 2000 0.08

Downstream (Reference) 177.5 2000 0.09 78.9 2000 0.04 All non-spill (Reference) 167.0 2000 0.08 67.8 2000 0.03

Spill locations (Exposed) 90.6 2000 0.05 25.1 2000 0.01 Phase II Upstream (Reference) 40.9 2000 0.02 453.1 2000 0.23

Downstream 234.4 2000 0.12 98.9 2000 0.05 All non-spill 228.1 2000 0.11 96.8 2000 0.05

Spill locations (Exposed) 94.1 2000 0.05 26.7 2000 0.01 1 EC= Exposure Concentrations, which are the measured values collected in the sampling discussed in Section 4. The water

values are means, tissue values are the 95% UCL of the mean.

All of the HQ values for the risk from exposure to mercury in water at the Reference and Exposed

locations are equal to 0.09, indicating minimal risk to aquatic biota from water. The HQ values calculated

for tissue concentrations are all less than 0.25, which also indicates minimal risk to aquatic biota from

mercury in tissue. The highest calculated HQ value of 0.23 for macroinvertebrate tissues is for samples

collected at upstream Reference locations in the Phase II sampling effort. The highest calculated HQ

values for fish tissue are 0.09 and 0.12 from the Phase I and Phase II samplings at locations downstream

of the spill area. These values are highly influenced by the tissue concentrations in fish and

macroinvertebrates collected at the Gallito Ciego Reservoir.

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It is not surprising to find higher mercury concentrations in aquatic biota from the reservoir. There is an

extensive body of evidence in the literature that documents a trend of naturally occurring higher tissue

concentrations of mercury in biota sampled from recently impounded reservoirs. Tissue concentrations in

fish naturally spike upwards initially after the creation of a reservoir, and then decline as the reservoir

ages. Omnivorous fish species (i.e., fish that eat plants and animals) are predicted to return to background

in 15 to 20 years, whereas piscivorous fish (e.g., predatory fish) are expected to take 20 to 30 years

(Anderson et al. 1995). For a reservoir in Labrador, Canada, mercury concentrations in the omnivorous

lake whitefish (Coregonus clupeaformis) returned to background in 16 years, though concentrations in

the piscivorous pike fish (Esox lucius) were still elevated 21 years after impoundment (Anderson et al.

1995). In a second reservoir in Labrador, mercury concentrations in whitefish increased for eight years

after the creation of the reservoir, and then started to decrease. However, in the same reservoir, pike

continued to increase in concentration 14 years after the creation of the reservoir (Morrison and Therien

1995). The Gallito Ciego reservoir was created approximately 15 years ago.

There are two primary suspected mechanisms that explain the increase in mercury in fish tissue collected

from impounded reservoirs. The first is that inorganic mercury in the flooded soils is released into the

water column, and is available for uptake by fish and prey items. This initial release is followed by the

second mechanism, which is the creation of anoxic conditions due to the flooding. Anoxic conditions,

along with the presence of organic material in the soil, allow for the methylation of any mercury that was

not initially dissolved in the water. The methylated mercury is subsequently transferred into the food chain

(Povari and Verta 1995).

In summary, there are no indications that surface waters or aquatic biota have been impacted by the spill.

The surface water data cover the period from June 2000 through April 2002. The tissue concentrations

are from sampling conducted in 2000, prior to the inception of the wet season, and in 2001 after the end of

the first wet season. The concentration of mercury measured in the surface waters at Reference and

Exposed locations are essentially the same (0.017 ppb), and are significantly less than the established safe

benchmark water level of 0.2 ppb for aquatic life. Additionally, the measured mercury concentrations in

all of the fish and macroinvertebrate tissue samples are less than the established benchmark concentration

of 2000 ppb (ww).

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5.2 Human Health The most likely mercury exposure routes to humans in the area around the spill sites are the inhalation of

elemental mercury vapor and the ingestion of water or food that have been impacted by the spill. As

discussed in Section 3.1, the potential risk to humans from inhalation has been previously addressed in

other reports (Consulcont SAC 2000, SMI 2002), and is not considered further in this RA. The primary

routes for ingestion of mercury are from drinking water or from the consumption of food, including plants,

terrestrial animals, and aquatic biota (fish and aquatic macroinvertebrates).

Table 5.2.1 summarizes the calculated HQ values for human exposure. HQ values are calculated for

exposure to mercury in drinking water and different dietary items, at both Exposed and Reference

locations, for all of the sampling efforts discussed in Section 4. The HQ for the risk from drinking water at

both Exposed and Reference locations is 0.02, indicating minimal risk from this exposure pathway.

Dietary HQ values were calculated for the consumption of fish, aquatic macroinvertebrates (crabs),

plants, and terrestrial animals. The ECs shown in Table 5.2.1 for terrestrial animal tissue were calculated

by multiplying the 95% UCL of the mean plant tissue mercury concentration by the bioaccumulation factor

(BAF) of 1.68 for mammals and 2.36 for birds (Section 4.5). Herbivores are the lost likely type of

terrestrial animal to be consumed by humans (Figure 2.3.1). For the range of values listed in Table 5.2.1,

the low end is for herbivorous mammal tissue and the upper end is for herbivorous bird tissue. All of the

dietary HQ values for all three sampling efforts are less than 1. The single highest dietary HQ of 0.76 is

for the consumption of fish tissue collected at non-spill sites during the Phase II sampling effort.

It is unlikely that carnivorous animals (i.e., animals that eat other animals) constitute a significant

proportion of the diet for humans living near the spill areas. However, assuming the highest predicted

mercury concentration of 443.5 ppb in herbivorous mammal tissue, as predicted from the November 15,

2000 plant sampling, and utilizing the same BAF of 1.68 for transfer of ionic mercury to mammal tissue,

results in a predicted mercury concentration in the tissue of carnivorous mammals of 745 ppb (ww; 443.5

ppb in tissue * 1.68). This concentration is also less than the average safe dietary level of 1600 ppb (HQ=

0.47). While there are no known piscivorous mammals, such as otters or mink, that live in the area (Table

2.2.1), there are piscivorous birds, such as herons, that might be eaten by humans. Using the highest 95%

UCL of the mean mercury concentration in fish tissue of 228.1 ppb (ww; Table 5.1.1), from fish collected

at downstream locations in the Phase II sampling, and the bird BAF of 2.36, results in a predicted mercury

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concentration in the tissue of fish-eating birds of 538 ppb (ww; 228.1 ppb in fish * 2.36). This predicted

concentration is less than the average safe dietary concentration of 1600 ppb, and results in an HQ of

0.34.

Table 5.2.1 Calculated Hazard Quotients (HQs) for Humans

EC1 Benchmark ppb (ww) ppb (ww) HQ

WATER Reference 0.017 1.0 0.02 Exposed 0.017 1.0 0.02

DIET Phase I-Reference Sites

Fish 167.0 300 0.56 Macroinvertebrates (crabs) 67.8 300 0.23 Plants (ww) 29.4 1600 0.02

Terrestrial animals* 49.4-69.4 1600 0.03-0.04 Phase I-Exposed Sites

Fish 90.6 300 0.30 Macroinvertebrates (crabs) 25.1 300 0.08 Plants 156.6 1600 0.10

Terrestrial animals* 263.1-621 1600 0.16-0.39 November 15, 2000 Sampling

Plants 264.0 1600 0.17 Terrestrial animals* 443.5-623 1600 0.28-0.39

Phase II-Reference Sites Fish** 228.1 300 0.76 Macroinvertebrates (crabs)** 96.8 300 0.32 Plants 7.9 1600 0.00

Terrestrial animals* 13.3-16.5 1600 0.01 Phase II-Exposed Sites

Fish 94.1 300 0.31 Macroinvertebrates (crabs) 26.7 300 0.09 Plants 9.8 1600 0.01

Terrestrial animals* 16.5-23.1 1600 0.01 1 EC= Exposure Concentrations, which are the measured values collected in the sampling discussed in Section 4. The water values are means, tissue values are the 95% UCL of the mean. * Calculated using BAF of 1.68 for transfer to mammal tissue and 2.36 for transfer to bird tissue (Section 4.5) ** All non-spill locations (Upstream and Downstream)

In summary, there is no evidence that the surface waters near the spill locations have been impacted by

the spill. The ambient mercury concentrations in the water are low and do not pose risk to humans via the

drinking water pathway. Additionally, the consumption of both aquatic and terrestrial dietary items pose

minimal risk to humans. While some individual fish or plant samples exceeded the established benchmark

values, a conservative estimate of the mean dietary concentrations (95% UCL of the mean) indicates that

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there is a low risk potential from dietary mercury. Two of the 154 Phase I plant samples, both of non-

edible plants, and none of the Phase II plant samples exceeded the human benchmark value of 1600 ppb

(ww). None of the Phase I nor Phase II crab samples exceeded the human dietary methylmercury

benchmark of 300 ppb (ww). Nine of the 137 Phase I and 13 of the 114 Phase II fish samples exceeded

the human dietary methylmercury benchmark of 300 ppb. All but two of these samples occurred

downstream of the spill area, with over 60% (14 samples) of the exceedances from Gallito Ciego

Reservoir samples.

5.3 Terrestrial Resources

The two primary types of terrestrial receptors that were considered in the RA are plants and animals.

5.3.1 Plants

The potential risk to plants was assessed for mercury concentrations in both soil and plant tissue. Results

of the HQ calculations for the three sampling efforts are shown in Table 5.3.1. The highest calculated

HQ value for soil of 0.07 is from the November 15, 2000 sampling. The same is true for the tissue HQs,

with the highest calculated HQ value of 0.28, also from the November 15, 2000 sampling event. None of

the measured soil concentrations, at any date or sampling location, exceeded the benchmark value of

10,000 ppb (dw) for soil. Three plant samples out of a total of 154 samples (2%) collected in the Phase I

sampling exceeded the tissue benchmark of 3000 ppb (dw). In the November 15, 2000 sampling, one

sample out of 24 (4%) exceeded the 3000 ppb (dw) benchmark. None of the 130 plant samples collected

in the Phase II sampling effort exceeded the benchmark value for mercury in plant tissues.

Table 5.3.1 Calculated Hazard Quotients (HQs) for Plants

EC1 Benchmark ppb (dw) ppb (dw) HQ

SOIL Reference 105.6 10000 0.01 Phase I Exposed 53.9 10000 0.01

November15, 2000 Sampling Exposed 743 10000 0.07 Reference 62.8 10000 0.01 Phase II Exposed 60.3 10000 0.01

TISSUE Reference 76.5 3000 0.03 Phase I Exposed 472.2 3000 0.16

November15, 2000 Sampling Exposed 838 3000 0.28 Reference 35.7 3000 0.01 Phase II Exposed 28.4 3000 0.01

1 EC= Exposure Concentrations, which are the measured values collected in the sampling discussed in Section 4.

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5.3.2 Animals For approximately the first month after the spill occurred, animals in the area may have been exposed to

mercury via inhalation. However, with the exception of domestic animals that were kept inside of houses

that were contaminated with the spilt mercury, animals would have had low inhalation exposure since the

evaporating mercury would be rapidly dispersed into the atmosphere, limiting the possible exposure

concentrations of mercury in the air. It is uncertain if any domestic animals were present in the homes

that were identifed as requiring remediation. If animals were present in any of these homes, however, the

potential inhalation risk would have been negated upon completion of the house remediation. More likely

exposure routes to animals (mammals and birds), especially over a longer timeframe, are from ingestion of

mercury in water and food.

Calculated drinking water and dietary HQ values for terrestrial mammals and birds are shown in Table

5.3.2. Potential dietary items for terrestrial animals are plants, insects, other terrestrial animals, fish, and

macroinvertebrates. Because there are no known mammals that eat fish or macroinvertebrates in the

area (Table 2.2.1), the modeled ECs listed in Table 5.3.2 for Other Terrestrial Animal tissue, are only for

the consumption of herbivores (plant-eaters) or insectivores (insect-eaters) by secondary consumers

(carnivores). The range of EC values listed for the Other Terrestrial Animal dietary type were calculated

by multiplying the 95% UCL of the mean concentration of mercury in the diet (plants and insects) by the

BAF factors established in Section 4.5. For the November 15, 2000 sampling, only secondary consumption

of herbivores was considered, since no insect tissue measurements were taken (Section 4.3), thus

preventing the calculation of mercury transfer to the tissues of insect-eating mammals and birds.

All of the calculated drinking water HQs (0.02) for birds and mammals were less than 1. The calculated

dietary HQs were also all less than 1, indicating a low risk potential from the diet. The highest mammal

dietary HQ of 0.84 is from the consumption of fish tissue collected in non-spill areas in the Phase II

sampling. The highest bird dietary HQ of 0.39 is for the consumption of insect-eating birds by other birds,

as based on the Phase I sampling of insect tissues at Exposed Sites.

In the Phase I sampling, a few individual samples exceeded either the mammal or bird dietary benchmark

values. However, the frequency of benchmark exceedance is low (< 3%) for all of the potential dietary

items (plants, insects, fish, and macroinvertebrates). Four of the 154 plant samples exceeded the mammal

dietary benchmark, though only two samples exceeded the bird benchmark. One insect sample, out of 45,

exceeded the bird dietary benchmark. None of the macroinvertebrate samples, and only one fish sample

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exceeded the benchmark values for birds. For the Phase II sampling, none of the plant, insect, or

macroinvertebrate samples exceeded dietary benchmarks, and only three of 114 fish samples exceeded

the benchmark for birds. All three of these fish samples were collected in the Gallito Ciego Reservoir.

Table 5.3.2 Calculated Hazard Quotients (HQs) for Terrestrial Animal Diets

MAMMALS BIRDS EC1 Benchmark EC1 Benchmark

ppb (dw)2 ppb (dw)2 HQ ppb (dw)2 ppb (dw)2 HQ

WATER

Reference 0.017 1.0 0.02 0.017 1.0 0.02 Exposed 0.017 1.0 0.02 0.017 1.0 0.02

DIET

Phase I-Reference Plants 76.5 2000 0.04 76.5 4000 0.02 Insects 167.9 2000 0.08 167.9 4000 0.04 Other Terrestrial Animals* 128.5-282.1 2000 0.06-0.14 180.5-396.2 4000 0.05-0.10 Fish 695.8 1100 0.63 695.8 2500 0.28 Macroinvertebrates 304.9 1100 0.28 304.9 2500 0.12

Phase I-Exposed Plants 472.2 2000 0.24 472.2 4000 0.12 Insects 663.2 2000 0.33 663.2 4000 0.17 Other Terrestrial Animals* 793-1114 2000 0.40-0.56 1114-1565 4000 0.28-0.39 Fish 377.5 1100 0.34 377.5 2500 0.15 Macroinvertebrates 268.9 1100 0.24 268.9 2500 0.11

November 15, 2000 Sampling Plants 838.0 2000 0.42 838.0 4000 0.21 Other Terrestrial Animals* 1407.8 2000 0.70 1977.7 4000 0.49

Phase II-Reference Plants 35.7 2000 0.02 35.7 4000 0.01 Insects 57.5 2000 0.03 57.5 4000 0.01 Other Terrestrial Animals* 60.0-96.6 2000 0.03-0.05 84.3-135.7 4000 0.02-0.03 Fish** 923.5 1100 0.84 923.5 2500 0.37 Macroinvertebrates** 274.9 1100 0.25 274.9 2500 0.11

Phase II-Exposed Plants 28.4 2000 0.01 28.4 4000 0.01 Insects 28.0 2000 0.01 28 4000 0.01 Other Terrestrial Animals* 47.7 2000 0.02 66.1 4000 0.02 Fish 419.1 1100 0.38 419.1 2500 0.17 Macroinvertebrates 127.0 1100 0.12 127.0 2500 0.05

1 EC= Exposure Concentrations, which are the measured values collected in the sampling discussed in Section 4. The water values are means and the tissue values are the 95% UCL of the mean. 2 the dietary EC and benchmark values are in dry weight, water comparisons are on a wet weight basis * The range of animal tissue concentrations is based on the BAF values from Section 4.5 and the plant and insect tissue concentrations (diet) ** The Phase II fish and macroinvertebrate ECs are for all non-spill sampling locations (Upstream and Downstream)

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In addition to water and dietary benchmarks, terrestrial animal tissue benchmarks were also established in

Section 3. The calculated ECs for animal tissue in Table 5.3.2 can be compared to the established

benchmarks of 3700 ppb (dw) for mammal tissue and 6000 ppb (dw) for bird tissue (Section 3.2.1). The

calculated HQ values based on these ECs are shown in Table 5.3.2. Also shown on Table 5.3.2 are HQ

values for the measured concentrations of mercury in insect tissue.

Table 5.3.3 Calculated Hazard Quotients (HQs) for Terrestrial Animal Tissues

MAMMALS BIRDS INSECTS EC1 Benchmar

k EC1 Benchmar

k EC1 Benchmar

k

ppb (dw) ppb (dw) HQ ppb (dw) ppb (dw) HQ ppb (ww)

ppb (ww) HQ

Phase I 128.5-282.1 3700 0.03-0.08 180.5-396.2 6000 0.03-0.07 63.8 150 0.43 Reference

Exposed 793-1114 3700 0.21-0.30 1114-1565 6000 0.19-0.26 252 150 1.68

November 15, 2000 Sampling Exposed 1407.8 3700 0.38 1977.7 6000 0.33 NA 150

Phase II 60.0-96.6 3700 0.02-0.03 84.3-135.7 6000 0.01-0.02 20.5 150 0.14 Reference

Exposed 47.7 3700 0.01 66.1 6000 0.01 13.2 150 0.09 1= Exposure Concentrations, which are the 95 % UCL of the measured or modeled values collected in the sampling discussed in Section 4. NA= Not analyzed

All of the calculated HQ values for the risk from mercury in mammal and bird tissues are less than 1. The

highest HQ of 0.38 for mammal tissue is based on the transfer of mercury to tissues from plant material

collected during the limited November 15, 2000 sampling. The highest HQ of 0.33 for assessing risk

associated with mercury in bird tissue also results from modeling of the transfer of mercury from plant

material that was collected during the November 15, 2000 sampling. The HQ value of 1.68 for insect

tissue collected in the Phase I sampling of Exposed Sites exceeds a value of 1, indicating that there may

have been potential risk to insects from mercury concentrations in their tissues. However, the calculated

HQ for the Phase II sampling effort, which collected insects at the same locations as Phase I, is less than

1, indicating that any risk to insects was temporary.

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6.0 SUMMARY AND CONCLUSIONS

6.1 Summary

The primary conclusion of the RA is that, with the possible exception of insects in 2000, there are no

unacceptable risks identified for aquatic biota, human health, or terrestrial ecological resources associated

with the mercury spill that occurred on June 2, 2000 along the road between Cajamarca and the Pan

American highway. This finding is not unexpected given the extensive and comprehensive response and

spill cleanup activities conducted by MYSRL (MYSRL 2001). The best estimates of the amount of the

151 kg of mercury spilt, not accounted for, is six to nine kilograms. This amount of mercury has a volume

of 0.67 L. This volume is either widely dispersed over the 40 Km spill area, or partially in the possession

of individuals.

The RA outlined four assessment endpoints, or environmental values (Section 2.4) that were to be

evaluated in the risk assessment. The conclusions associated with these assessment endpoints are

summarized in Table 6.1.1. Further discussion on each of the assessment endpoints is provided.

6.2 Human Health

The first assessment endpoint is associated with protecting the health of the human population living in and

around the spill area. The RA only addressed the risk to humans from ingestion of mercury in water and

food since previous reports have evaluated inhalation risk to residents (Consulcont SAC 2000, SMI 2002).

There was and is minimal risk to humans from the ingestion of mercury in food and drinking water.

There is no evidence that mercury from the spill was mobilized into the surface waters in the

Jequetepeque watershed. The concentration of mercury from both Reference and Exposed locations are

equivalent and low. The mean concentration of 0.017 ppb in water is less than the drinking water

benchmark for humans of 1.0 ppb, indicating that there is minimal risk to humans from the direct

consumption of mercury in drinking water (Table 5.2.1). Additionally, the sampling effort conducted from

just after the spill through the end of the second wet season demonstrated that mercury from the spill was

not mobilized into the surface waters near the spill locations.

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Table 6.1.1 Conclusions From Assessment Endpoints, Measures of Effect, and Exposure Assessment Endpoint Measures of Effect and Exposure Conclusions



Risk from ingestion of fish, crabs, plants and drinking water is minimal; HQs<1.



Risk from ingestion of terrestrial mammals and birds is minimal; HQs<1.




Risk to plants from mercury in soil or in tissues is minimal; HQs<1.


Risk to mammals and birds from water and dietary consumption is minimal; HQs<1.

Survival, growth, and reproduction of populations of terrestrial animals that may be exposed to mercury from drinking water, consumption of plants, or consumption of other animals Indirect measures of exposure: modeled

concentrations of mercury in terrestrial animal tissue using literature transfer factors

Risk to mammals and birds from mercury tissue concentrations is minimal; HQs<1. Potential risk to insects in 2000, risk in 2001 is minimal; HQ<1.




Risk to aquatic biota from water and tissue concentrations of mercury is minimal; HQs<1.

HQ= Hazard Quotient (discussed in Section 5, indicates minimal risk if HQ<1)

In most diets, fish and shellfish account for a significant proportion of mercury ingested (Section 3.1).

Because of this fact, and since essentially all of the mercury in the tissues of aquatic biota is in the more

available and toxic methylmercury form (WHO 1991), many governmental agencies and organizations

have established safe levels of mercury in fish tissue for human consumption (Table 4.1.2). The lowest of

these values, 300 ppb (ww; Table 3.1.2) was used as the benchmark to evaluate risk. The mean values

from both Exposed and Reference locations from the Phase I and Phase II sampling efforts are typical of

the mercury concentrations measured in fish and shellfish consumed in the diet of people in the USA,

Canada, Scotland, Italy, and Spain (Table 1.2.3). Additionally, the 95% UCL of the mean concentrations,

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which is a conservative estimate of exposure, indicates that mercury levels in fish and crabs pose minimal

risk to humans (Table 5.2.1). This result is in agreement with the evidence that mercury from the spill was

never mobilized into the surface waters near the spill locations.

A protective average dietary mercury concentration of 1600 ppb was established for non-fish food items in

the diet of humans (Section 3.1). The Phase I sampling found that the mercury concentrations in

vegetation collected at the Exposed locations tended to have higher mercury concentrations than samples

from Reference locations. The 95% UCL of the mean concentration of mercury in the diet at all

locations, however, were below the benchmark level and pose minimal risk to humans (Table 5.2.1). The

Phase II sampling, which was conducted during the second wet season, found much lower levels of

mercury in vegetation collected from both Reference and Exposed locations (Table 5.2.1). Soil mercury

concentrations were essentially constant between the Phase I and Phase II sampling efforts (Table 5.3.1).

This finding shows that there is a seasonal component to mercury concentrations in vegetation. The likely

explanation is that dry deposition of mercury onto plant surfaces, probably as particulates from 1) wood

and garbage burning, 2) vehicle emissions, and 3) dust from soils that naturally contain mercury causes the

seasonal variability (Hanson et al. 1995, Jones and Slotton 1996). During the wet season, the frequent

rains reduce the levels of particulates in the air and wash deposited mercury from the surface of the

plants, reducing the measured concentrations.

Modeled mercury concentrations in animal tissue, which result from the consumption of plants, by animals

that are subsequently consumed by humans, were also below the dietary benchmark concentration for

humans (Table 5.2.1). This further indicates minimal risk to humans from the dietary consumption of

mercury.

6.3 Agricultural and Native Plants The second assessment endpoint is for the protection of the survival, growth, and reproduction of native

and agricultural plants. Based on the literature (Section 3.2.2), plant toxicity would likely be manifested by

a reduction in the rate of growth, not the overall survival or viability of plants (i.e., mercury will not kill the

plant). There was and is minimal risk to plants as evaluated from concentrations of mercury in soil and

from the concentrations of mercury in plant tissues.

Early research on mercury levels in plants identified soil as the primary source of mercury to plants

(Warren et al. 1966). More recent work, however, has shown that foliar absorption and dry deposition are

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important contributors to mercury in plant tissue (Hanson et al. 1995, Patra and Sharma 2000). The results

of the Phase I and Phase II soil sampling efforts indicate that there is no general increase in mercury

concentrations in soils from the Exposed sites relative to Reference locations. For both of these sampling

efforts, the 95 % UCL of the mean concentration of mercury in soils from the Exposed locations was less

than the Reference locations (Table 5.3.1). Moreover, the concentrations at all locations are below the

soil benchmark value of 10,000 ppb (dw) and are typical of normal background levels of mercury in the

environment (Section 1.2.3).

As previously discussed, vegetation samples collected at Exposed locations during the Phase I sampling

tended to have higher mercury concentrations than samples from Reference locations collected at the

same time (Table 5.3.1). However, mercury concentrations in less than 2% of the collected samples

exceeded the benchmark value for mercury in plant tissue of 3000 ppb (dw). Mercury concentrations in

plant tissues collected in the Phase II sampling effort, from both Reference and Exposed locations, were

much lower than the Phase I samples (Table 5.3.1). The Phase II samples were collected during the wet

season (February 2002), whereas the Phase I samples were collected at the end of the dry season

(September 2000). Given that the Phase I plant tissue concentrations were higher at the Exposed

locations than at the Reference locations, even though the co-located soil mercury concentrations were

lower at the Exposed locations, and that the concentrations at both Reference and Exposed locations

dropped significantly during the wet season, it is apparent that uptake from soil is not the primary exposure

route to plants. Dry deposition of mercury from a variety of sources seems to be the primary driver of

mercury levels in plants.

6.4 Terrestrial Animals The third assessment endpoint for the RA is the protection of the survival, growth, and reproduction of

terrestrial animals. The RA evaluated the risk to terrestrial animals from exposure to mercury in drinking

water, in the diet, and in their tissues. The risk from all of these exposure pathways was and is minimal,

with the exception of terrestrial insects during the first dry season (Tables 5.3.2 and 5.3.3). The 95%

UCL of the mean concentration of mercury in insect tissue collected in the Phase I sampling exceeded the

benchmark value of 150 ppb (ww; Table 5.3.3). The Phase II sampling, however, indicated that if there

was any risk to insects based on the tissue concentrations measured in Phase I, the risk was no longer

present.

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It is generally reported that, with the exception of inhalation exposure, the toxicity of elemental mercury to

animals is low, primarily due to strong soil adsorption and low gastrointestinal absorption in animals (Amdur

et al. 1991). In addition, terrestrial pathways of mercury exposure are generally considered to be of lower

concern than aquatic pathways because: 1) terrestrial pathways generally involve inorganic mercury rather

than methylmercury, 2) uptake of inorganic mercury is limited in plants and soil invertebrates, and 3) the

mercury that is ingested by birds and mammals tends to be stored in fur and feathers which are not

consumed by higher-order consumers or are poorly digested if consumed (USEPA 1997a).

Only a few individual dietary samples from the Phase I and Phase II sampling events exceeded either the

mammal or bird dietary benchmark values. The frequency of benchmark exceedance was low (< 3%) for

all of the potential dietary items (plants, insects, fish, and macroinvertebrates). Four of the 154 Phase I

plant samples exceeded the mammal dietary benchmark of 2000 ppb (dw), though only two of these

samples exceeded the bird benchmark of 4000 ppb (dw). One Phase I insect sample, out of 45, exceeded

the bird dietary benchmark. None of the Phase I macroinvertebrate samples, and only one fish sample

exceeded benchmark values for birds. For the Phase II sampling, none of the plant, insect, or

macroinvertebrate samples exceeded dietary benchmarks, and only three of 114 fish samples exceeded

the benchmark for birds. All three of these fish samples were collected in the Gallito Ciego Reservoir,

where mercury was present as a result of the water impoundment, prior to the spill.

6.5 Aquatic Resources The final assessment endpoint is aimed at the protection of aquatic biota in the waterways around the spill

area. The risk from concentrations of mercury in water and in tissues of fish and aquatic

macroinvertebrates was and is minimal. The RA considered mercury concentrations measured in surface

water from the inception of water sampling, which was first conducted during the week of June 15,

through April of 2002. This time period includes sampling conducted prior to the inception of the first rainy

season after the spill (essentially November 2000), through the end of the second wet season (April 2002).

Phase I tissue sampling was conducted prior to the first season and therefore before the spilt mercury

could be mobilized. Phase II tissue sampling occurred after the end of the first wet season and served to

evaluate whether or not mercury levels in the aquatic systems had increased.

There has been no indication of any mercury mobilization from the spill sites into the waterways. The

mean mercury concentration in water collected from Reference locations is equal to the mean

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concentration of 0.017 ppb from the Exposed locations. The mean sediment mercury concentration of

112.4 ppb (ww) from the Exposed locations is lower than the mean concentration of 177.9 ppb (dw) from

the Reference locations (Section 4.1).

The tissue concentrations of mercury in fish and aquatic macroinvertebrates are similar to the water and

sediment results, with generally higher mercury concentrations observed in tissues collected from non-spill

locations (upstream and downstream) than in samples collected near the spill areas (Table 5.1.1). Some of

the highest mercury concentrations in aquatic biota were measured in samples collected from the Gallito

Ciego Reservoir. It is well documented in the scientific literature that mercury concentrations in biota

collected from recently created reservoirs, such as the Gallito Ciego, become naturally elevated (Section

5.1). Essentially, the elevated tissue concentrations are a result of the mobilization of natural

concentrations of mercury in the flooded soils.

6.6 Uncertainty In order to minimize the impact of uncertainty associated with assumptions made in the RA, wherever

possible, conservative assumptions have been made. Examples of this conservatism include: 1) utilizing

the detection limits, for samples recorded as being less than detection, in the calculation of means, 2) using

the 95 % UCL of the mean for estimating Exposure Concentrations, and 3) assuming the higher of either

methyl or total mercury concentrations reported for fish samples in evaluating exposure and effects.

Specific sources of uncertainty are discussed in greater detail below.

There are several areas of uncertainty associated with the data utilized in the risk assessment. The

potential biggest source of uncertainty is associated with the data collected by SENASA and Consulcont

SAC (Appendix A). As discussed in Section 4, because of the high degree of uncertainty associated with

these data, they were not utilized in the RA. It is important to note, however, that the sampling that was

conducted jointly by SENASA, MYSRL, and SMI in November of 2000, at the same locations where the

earlier SENASA sampling had reported elevated mercury concentrations in plants, was utilized in the RA.

Additionally, the 95% UCL of the mean concentrations recorded by SENASA and Consulcont are all

below the benchmark concentrations. All of the recorded fish tissue concentrations are less than 50 ppb,

all of the water concentrations are reported as 0.00 ppb, and the highest soil concentration reported is 8.27

ppb (Appendix A). The mean and 95% UCL of mean mercury concentrations in animal tissue

concentrations are 17.3 ppb and 35.7 ppb, respectively. None of these concentrations exceed any of the

benchmark values (Table 3.4.1). The mean and 95% UCL of mean mercury concentrations in vegetation

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are 668.6 ppb and 1256 ppb. As previously discussed, it is unclear if the tissue values are on a wet weight

or dry weight basis. Assuming that they are reported as dry weight concentrations, none of the benchmark

values (Table 3.4.1) are exceeded. If they are on a wet weight basis, the 95% UCL of the mean plant

tissue concentration does not exceed the human dietary benchmark. Without knowing the moisture

content of the samples, it cannot be determined if they exceed the mammal and bird dietary benchmarks.

Another source of uncertainty associated with the data are the reported methylmercury concentrations in

aquatic biota that were greater than the total mercury levels reported for the same sample. Frontier

Geosciences believes that the different analyses required to measure methylmercury and total mercury

result in this apparent discrepancy (Appendix G). To overcome this uncertainty, the higher of the values

(either methyl or total) was used in calculating the Exposure Concentrations in the RA.

The last potentially significant uncertainty associated with the data is the modeled concentrations of

mercury in terrestrial animal tissues. Only limited direct measurements of mercury in terrestrial animal

tissues were made during the November 2000 sampling (Section 4.3). In order to assess the risk

associated with mercury in terrestrial animal tissues, as well as to evaluate the risk from the consumption

of terrestrial animal tissue, literature bioaccumulation factors (BAFs) were used to model the expected

tissue concentrations. While there is some uncertainty with this approach, conservative assumptions were

made including the use of the 95% UCL of the mean for the dietary concentrations for the transfer of

mercury to tissues.

There is overall a low degree of uncertainty associated with the benchmark values since conservative no

observed adverse effect levels (NOAELs) were selected as the threshold levels for evaluating risk. The

benchmark value established for mercury in insect tissue (Section 3.2.1), however, has greater uncertainty

since it was derived by dividing a lethal effect level by an uncertainty factor of 50, as recommended by

Calabrese and Baldwin (1993). While the use of a large safety factor makes it unlikely that effects would

be expected at a lower level than the benchmark established, higher concentrations may also result in no

adverse effects to insects.

The last major source of uncertainty is associated with the long term fate of any mercury that remains in

the environment. Based on the results of studies conducted at locations in the USA (e.g., Oak Ridge

National Laboratory and Carson River), spilt elemental mercury can remain in the elemental form in the

environment even decades after a spill has occurred (Campbell et al. 1998, Carroll et al. 2000, Gustin et al.

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1995). Because elemental mercury has very low solubility in water (Table 1.2.1) it is unlikely to be

dissolved and mobilized to other locations. Any mercury that is oxidized to form ionic mercury, will likely

be strongly absorbed to the soil, again limiting potential migration (WHO 1989, 1991). However, even if it

is assumed that the potentially maximum amount of mercury that remains in the environment (9 kg) is

mobilized at one time to the Gallito Ciego Reservoir, the potential risk is still minimal. Based on the volume

of the reservoir listed by Loayza (1999) of 400.4 million cubic meters, the addition of 9 kg of mercury

dissolved in this volume of water would result in an incremental increase in mercury concentrations of 0.02

ppb. This increase would not result in any significant additional risk to aquatic biota or to terrestrial

consumers of drinking water.

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