1

Bioaccumulation Factor for Polychlorinated Biphenyls in Fish in

the Houston Ship Channel

Civil and Environmental Engineering Research Experience for Undergraduates

University of Houston

Prepared by:

Sean Carbonaro

Dr. Hanadi Rifai

July 30, 2009

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Abstract

Polychlorinated biphenyl (PCB) concentrations in water, sediment and fish

samples were studied in the Houston Ship Channel and Galveston Bay to determine a

bioaccumulation factor (BAF) for common fish species. The objective of the study was to

test the validity of the use of a simple BAF parameter in water quality regulation. Water

PCB concentration was found using a high-volume sampling technique. Fish were

filleted for tissue analysis. A general decline in PCB levels from 2002-2003 to 2008

across all media was found in the studied area. In the 2008 study, 96% (n=25) of the

stations sampled exceeded the PCB standard for fish tissue and/or water. A strong linear

correlation was found between total water concentration and lipid-normalized tissue

concentration of PCBs for Atlantic Croaker (R2=0.696, p<0.0005), while there was no

correlation for Hardhead Catfish (R2=0.022, p=0.563). In calculating a BAF (in L/kg

lipid) for both species, a lower mean and smaller range was found for Atlantic Croaker

(2.41·106, 1.19·106-4.12·106) than for Hardhead Catfish (7.02·106, 8.50·105-5.82·107) in

the 2008 data set. Similar results were found for Hardhead Catfish in the 2002-2003

study (5.65·106, 5.37·105-3.04·107). No correlation (R2=0.0029, p=0.862) was found

between the BAF of Atlantic Croaker and Hardhead Catfish at common sampling sites in

the 2008 study. A linear deterministic model was not found to be suitable to determine a

BAF that applied to both species.

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Table of Contents

1. INTRODUCTION .............................................................................................................................. 5

2. METHODS ......................................................................................................................................... 9

2.1 STUDY AREA ........................................................................................................................................ 9 2.2 SAMPLE COLLECTION ......................................................................................................................... 10 2.3 ANALYTICAL METHODS ..................................................................................................................... 12 2.4 DATA PROCESSING METHODS ............................................................................................................ 13

3. RESULTS AND DISCUSSION ........................................................................................................ 14

3.1 TEMPORAL VARIATION OF PCB CONCENTRATIONS IN WATER, SEDIMENT AND FISH TISSUE ................ 14 3.2 VARIABILITY OF BAF WITH FISH TISSUE CONCENTRATION AND WATER CONCENTRATION ................. 16

3.2.1 Lipid-normalized fish tissue concentration ................................................................................ 16 3.2.2 Water concentration ................................................................................................................... 18

3.3 CALCULATION OF BAF FOR HARDHEAD CATFISH AND ATLANTIC CROAKER ..................................... 20 3.4 COMPARISON OF SPECIES-SPECIFIC BAF............................................................................................. 24

4. CONCLUSIONS ............................................................................................................................... 27

ACKNOWLEDGEMENTS .................................................................................................................. 27

REFERENCES ..................................................................................................................................... 29

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1. Introduction

Polychlorinated biphenyls (PCBs) are a suite of chemicals that have been used for

a variety of industrial purposes, namely as dielectric fluids in transformers and capacitors,

and in hydraulic systems (Bodin et al., 2008). Large-scale industrial production began in

1929 with the creation of Arochlors, a family of PCB congeners with different levels of

chlorination (Lipnick et al., 2001). In 1976, the ban of PCB manufacturing, processing,

distribution and use began in the United States, followed by Japan, Canada and western

European countries (Lipnick et al., 2001). The prohibition of PCBs occurred as a result of

the discovery of the toxicological effects of PCBs exposure. The effects of PCBs were

found as early as 1937 when occupational exposure caused acute toxic health effects and

researchers reported that “these experiments leave no doubt as to the possibility of

systemic effects from … chlorinated diphenyl” (Drinker et al., 1937). Chronic toxicity

has yet to be proved, but toxicological data from animal studies tend to show that it is

indeed toxic and carcinogenic (Robertson and Hansen, 2001). It is important to note that

each congener has different toxicity, with more chlorinated congeners generally being

more toxic. The consequences of PCB exposure are observed mainly in the thyroid gland,

liver, immune system and reproductive system of humans (Sharma et al., 2009). The

majority of the attention to PCB toxicity occurred as a result of an incident in western

Japan in 1968. Cooking oil was contaminated with PCBs and 1291 patients reported toxic

effects including various somatic complaints, low birth weights, chloracne and

pigmentation (Robertson and Hansen, 2001). However, some additional studies have

suggested the observed effects have occurred as a result of co-contamination with more

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toxic compounds, such as polychlorinated dibenzofurans (PCDFs), which complicates

toxicological analysis (Robertson and Hansen, 2001).

The current standards for fish and water for PCBs in the state of Texas have been

set by the Texas Department of State Health Services (TDSHS) and Texas Commission

on Environmental Quality (TCEQ), respectively. The fish tissue standard is 0.047 mg/kg,

or 47 ng/g, measured on a wet weight basis (TDSHS, 2008a). The surface water quality

standard for areas with sustainable saltwater fisheries is 0.885 ng/L (TCEQ, 2008). The

surface water quality standard for freshwater areas designated or used for public drinking

water supply and recreational fishing is 1.3 ng/L (TCEQ, 2008). These standards are

currently below those set by the United States Environmental Protection Agency

(USEPA).

The ubiquitous nature of PCBs was reported by Jensen in 1966 with a study

indicating significant concentrations of PCBs in the tissue of eagles, herring, and other

environmental species in Swedish waters (Jensen et al., 1969). PCBs are persistent in

nature due to the high physical and chemical stabilities that made them attractive to

industry (Lin et al., 2006). This persistence along with their hydrophobicity and

resistance to degradation lends way to PCBs’ ability to bioaccumulate (Bodin et al.,

2008). The criteria for bioaccumulation is generally when the Bioaccumulation Factor

(BAF) exceeds 5000 L/kg on a wet weight basis, with the BAF being the ratio of

concentration in fish tissue to concentration of the water (Harrad, 2001). The BAF is used

by the USEPA in calculating a Water Quality Target (WQTarget) for a particular body of

water. Toxicological effects of PCBs generally occur from human consumption of

aquatic organisms, however the concentration of PCBs in the tissue of aquatic organisms

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cannot be easily monitored and regulated. The purpose of the BAF is to translate the

desired concentration in aquatic organism tissue into a water concentration, WQTarget, to

assist in the regulation process. The accuracy of the number used for BAF is important as

it relates to permitting and clean-up efforts.

The ability of a chemical to bioaccumulate has been related to several potential

factors. Substances will partition differently between fish tissue and water depending

upon their chemical properties, the most relevant of which is the octanol-water partition

coefficient (Kow). There are 209 different congeners of PCBs, over which there is a Kow

range of 105, with the more chlorinated congeners being more hydrophobic. This range of

chemical properties among PCB congeners themselves leads to the problem of

calculating a singular BAF for such a wide range of chemicals. Another important

consideration for calculating the BAF is the bioavailability of the PCBs. In the freely

dissolved phase, the contaminants are able to move freely across biological membranes

of aquatic organisms, while those in the suspended phase cannot (Sethajintanin and

Anderson, 2006). The study by Sethajintanin and Anderson, 2006 found bioavailability

varies greatly among PCB congeners, with some being consistently more bioavailable

than others.

In the calculation and understanding of the BAF, it has been accepted that lipid

normalization of the chemical concentration is essential (USEPA, 1995). United States

Environmental Protection Agency (USEPA) guidelines suggest that lipid content is

determined from the same sample that is analyzed for chemical residue (USEPA, 1995).

Bioconcentration tends to be proportional to the lipid content of the organism, and the use

of lipid normalization allows for the calculation of a BCF or BAF independent of the

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lipid content of the organism (Harrad, 2001). Based on the value of normalizing fish

tissue concentration with lipid content and using bioavailable, or dissolved phase, water

concentration, the equation that will be preferred in the calculation of BAF in this paper

will be as follows:

BAF =

Tissue PCB concentrationLipid content

Dissolved phase PCB concentration

In this study, it will be important to consider the vast differences between

congeners. Some congeners can potentially be neglected as their concentrations are

consistently very low in comparison to others due to the lack of industrial production and

other factors. Other congeners can also possible be neglected due to their low octanol-

water coefficient (Kow) since they likely do not partition into fish tissue as well as other

more chlorinated congeners. Several studies have been done to attempt to use log Kow as

a predictor of BAF, typically in the form of log BAF. It has been suggested that if

equilibrium partitioning between the water and fish tissue were to occur, log Kow would

be equal to log BAF (Borga et al., 2005). However Borga et al. 2005 found that the BAF

was at least 10 times higher than that predicted by Kow. A special case of

bioaccumulation is the bioconcentration factor (BCF), which like BAF is the ratio of

concentration in fish tissue to concentration of the water, but considers only abiotic

exposure and must be found in laboratory experiments. The relationship between log

BCF and log Kow has been found to be stronger and more reflective of the equilibrium

partitioning assumption than the relationship between log BAF and log Kow (Arnot and

Gobas, 2006). However, the BCF is not a realistic predictor of the true concentration in

aquatic organisms because it does not account for factors including diet and sediment

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interactions. The BAF has been found to be up to 10000 times greater than the BCF for

high Kow chemicals (Harrad, 2001). There has also been a parabolic correlation found

between log BAF and log Kow. A species-specific parabolic model more sufficiently

explained the relationship of log BAF to log Kow than a linear model in 4 out of 6 species

in a heavy polluted reservoir (Wu et al., 2008). No consensus has been found concerning

the relationship between BAF and Kow as many other factors contribute to the BAF

including the organism’s size, diet, behavior, and several other potential factors.

2. Methods

2.1 Study Area

The Houston Ship Channel (HSC), Upper and Lower Galveston Bay, and Trinity

Bay have received several advisories about fish consumption in recent years (TDSHS,

2008a) (TDSHS, 2008b). TDSHS has advised against the consumption of more than one

eight-ounce meal per month of all catfish species and speckled sea trout due to the

presence of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans

(PCDDs/PCDFs or ‘dioxins’) and polychlorinated biphenyls (PCBs). Galveston Bay is

the seventh largest estuary (600 square miles or 384,000 acres, 232 miles of shortline) in

the United States. Nearly half of all United States petrochemical production occurs in the

greater Houston area. A map summarizing the sample locations for the 2008 study is

included in Figure 1.

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Figure 1. Map of Houston Ship Channel, Galveston Bay, contributing bayous and

sample sites for 2008 study.

2.2 Sample Collection

Sampling was performed at the selected sites for two periods of time, from

summer 2002 to spring 2003, then again during 2008. In the summer 2002 to spring 2003

study, a sum total of 53, 98 and 84 samples were collected for water, sediment and fish,

respectively. In the 2008 study, a sum total of 45, 95 and 50 samples were collected for

water, sediment and fish, respectively. The selected sites were spaced throughout the

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HSC, adjoining bays, and Houston area bayous. At each site, samples were taken from

water, sediment and fish tissue to measure various parameters.

Water column samples were taken using a high-volume sampling technique. The

sampling unit that was used is designed to collect both particle-bound and dissolved

phase PCBs. This is achieved at low detection limits by the use of 1 µm Glass Fiber

Filters (GFFs), which collect the particle-bound PCBs, and XAD-2 resins, which collect

the dissolved phase PCBs. The sampling unit was operated continuously from a boat until

the desired volume of water was filtered. This desired volume of water can range from

100 L to 1000 L to detect ultra trace (well below 0.1 ppb, or 0.1 µg/L) concentrations. A

representative sample of the entire water column was ensured by changing the depth of

the sampling unit inlet every 30 minutes. Some in-stream sampling was performed by

operation of the sampling unit from the shore of the stream. These sampling points taken

from land are generally assumed to have no concentration deviation with depth. After the

desired volume is achieved, the GFFs and XAD-2 resins are packaged separately for

analysis. The Total Suspended Solids (TSS) samples were collected from a depth of 1 ft

using pre-cleaned glass bottles. The Dissolved Organic Carbon (DOC) and Total Organic

Carbon (TOC) samples were also collected from a depth of 1 ft using pre-cleaned

borosilicate glass bottles.

Sediment samples were taken using a stainless steel Ponar, Eckman, or Peterson

dredge. Prior to sample collection, the dredge, stainless steel spoon, and stainless steel

bucket were rinsed with de-ionized (DI) water, then ambient water. A minimum of three

sediment grab samples were collected from only the top 5 cm of sediment. A

representative sample of the water cross section was ensured by collecting samples in

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equal amounts from river left, right and center. The samples were then homogenized,

deposited into a labeled, pre-cleaned amber glass jar with a Teflon seal. Separate samples

were prepared to measure for Total Organic Carbon (TOC), solids content, and Total

Petroleum Hydrocarbons (TPH). The dredge was not used in the same area for all grab

samples, but rather various locations around the sampling boat or across the stream.

Fish tissue was collected from several species, with preference in the following

order; Trout/Croakers: Speckled Seatrout (Cynoscion nebulosus), Sand Seatrout

(Cynoscion arenarious), and Atlantic Croaker (Micropogonias undulates); Catfish:

Hardhead Catfish (Arius felis), Blue Catfish (Ictalurus furcatus), and Channel Catfish

(Ictalurus punctatus). Speckled Seatrout, Sand Seatrout and Atlantic Croaker were not

sampled in the 2002-2003 study. A target length of 30 cm, or 12 in, and larger was used

for collection. The samples were all individually measured for length and weight. A

composite of fish tissue from a minimum of three fish from the same species was

obtained by filleting fish samples using a stainless steel knife, packing in aluminum foil

and plastic bags, then freezing the composite. The composite was then shipped to a

commercial lab for analysis of PCB concentration and lipid content.

2.3 Analytical Methods

PCB congeners in water, sediment, and fish were quantified by high-resolution

gas chromatography/high resolution mass spectrometry (HRGC/HRMS) using USEPA

method 1668A, which quantifies all 209 congeners (USEPA, 1999). Lipid content was

determined by a commercial laboratory’s in-house method. Sediment TOC was

determined via USEPA Method 415.2. All of these analyses were completed by a

commercial laboratory.

a The 43 congeners, along with co-eluters, are PCB-8, 18/30, 20/28, 37, 44/47/65, 49/69, 52, 60, 61/70/74/76, 66, 77, 81, 82, 83/99, 86/87/97/109/119/125, 90/101/113, 105, 114, 118, 123, 126, 128/166, 129/138/163, 135/151, 153/168, 156/157, 158, 167, 169, 170, 177, 179, 180/193, 183, 187, 189 b The NOAA 18 congeners, along with co-eluters, are PCB-8, 18/30, 20/28, 44/47/65, 52, 66, 77, 90/101/113, 105, 118, 126, 128/166, 129/138/163, 153, 169, 170, 180/193, 187

2.4 Data Processing Methods

Data analysis was performed using databases containing the results from two

sampling sets from 2002 to 2003 and 2008. Two congener-specific grouping methods

were used in analyzing the data in addition to the total concentration method. One of the

methods used is a grouping of 43 specific congenersa (McFarland and Clark, 1989). The

other used was the NOAA 18b (NOAA, 1989). These congener groupings were found by

their respective sources to be of particular concern due to their ability to occur frequently

in environmental samples, accumulate in animal tissue, and display toxic effects.

Other considerations were taken in the use of the database. Duplicate samples

were taken at several of the sites used for this study. For those samples, the average of the

results were taken and used as a singular data point for that particular station. The

concentrations of the individual PCB congeners were reported separately and summed to

produce the results for all congeners, McFarland and Clarke 43a, and NOAA 18b. On

several samples the results of some congeners fell below the Method Detection Limit

(MDL). For these individual congener concentrations, the result was assumed to be one

half of the MDL. This method did not significantly change the results for the congener

concentration sums and was found to be the best option over assuming the non-detectable

samples to be zero or at the MDL.

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3. Results and Discussion

The fish tissue and surface water quality standards for PCBs were regularly

exceeded in the study area. In the 2008 study, 23 out of 25 stations sampled for water

concentration exceeded the TCEQ surface water quality standard of 0.885 ng/L. The

average total water concentration, using all congeners, was 2.22 ng/L. In the 2008 study,

22 out of the 25 stations sampled for catfish and/or sportfish exceeded the standard of 47

ng/g wet weight. The average fish tissue concentration for all fish species sampled, using

all congeners, was 174 ng/g wet weight. In the 2002 study, 27 out of the 32 stations

sampled for water concentration exceeded the water quality standard of 0.885 ng/L. The

average total water concentration, using all congeners, was 1.96 ng/L. In the 2002 study,

30 out of the 32 stations sampled for catfish exceeded the standard of 47 ng/g wet weight.

The average tissue concentration for all fish species sampled in the 2002 study, using all

congeners, was 129 ng/g wet weight.

3.1 Temporal variation of PCB concentrations in water, sediment and fish tissue

The studies in 2002-2003 and 2008 had 18 common stations that were sampled

for water, sediment and catfish tissue concentrations. Atlantic Croaker and Speckled

Seatrout were not sampled in the 2002-2003 study. A decline in the concentration of

PCBs across all media over time can be seen in Table 1. However, the concentrations of

the congener groupings in all water phases considered to be of most importance show less

of a reduction than when all congeners are included. This trend is not seen in sediment or

fish tissue. This could indicate that either the specific congeners identified by McFarland

and Clarke and NOAA are indeed more persistent, but only in the water phase, than other

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congeners or that the recent inputs of PCBs into the HSC have a congener profile more

representative of the specific congener groupings than the entire congener range. On a

lipid basis, the PCB concentration within the catfish tissue was relatively unchanged.

However, on a wet weight basis, the concentration was significantly reduced. This could

be indicative of a difference in selection criteria between the two studies or a possible

trend in the lipid content of the fillets of catfish in the HSC.

Table 1. Comparison of 2002-2003 and 2008 Data for various media

2002-2003 2008

Water (Total) (ng/L)

All congeners 2.58 1.98 23.1

M & C 43 1.10 0.91 17.3

NOAA 18 0.77 0.68 12.0

Water (Dissolved) (ng/L)

All congeners 1.68 1.55 8.0

M & C 43 0.74 0.69 6.4

NOAA 18 0.52 0.53 -1.2

Water (Suspended) (ng/L)

All congeners 0.89 0.43 51.6

M & C 43 0.36 0.22 39.5

NOAA 18 0.25 0.15 39.9

Sediment (ng/g)

All congeners 228 26 88.8

M & C 43 117 14 88.3

NOAA 18 78 9 87.8

Catfish tissue (ng/g ww)

All congeners 154 112 27.6

M & C 43 113 84 24.9

NOAA 18 86 63 26.7

Catfish tissue (ng/g lipid)

All congeners 9033 9023 0.1

M & C 43 6604 6871 -4

NOAA 18 5061 5135 -1.5

Year

Percent reduction (%)

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3.2 Variability of BAF with fish tissue concentration and water concentration

The lipid-normalized BAF was plotted against the lipid-normalized fish tissue

PCB concentration, total PCB water concentration, and dissolved phase PCB water

concentration. The regressions were performed on individual species of fish from the

study, the largest two groups being Atlantic Croaker and Hardhead Catfish.

3.2.1 Lipid-normalized fish tissue concentration

The regressions of lipid-normalized fish tissue concentration against lipid-

normalized BAF for Hardhead Catfish and Atlantic Croaker are shown in Figure 2. A

significant linear correlation (R2 = 0.8027, p<0.0005, 2 outliers removed) was found

between the lipid-normalized Hardhead Catfish tissue concentration and lipid-normalized

BAF for Hardhead Catfish. Another regression of lipid-normalized tissue concentration

against lipid-normalized BAF was also performed using the 2002 Hardhead Catfish data.

A significant linear correlation (R2=0.522, p<0.0005, 31 samples, 3 outliers removed)

was found using this Hardhead Catfish data as well. The range of water and fish tissue

concentration was comparable, as can be seen in Table 1. The relationship found from

this plot indicates that the BAF may not be independent of fish tissue concentration as

has been previously suggested. It is possible that in the particular water and fish tissue

concentration range in this study the PCB intake rate of the Hardhead Catfish far exceeds

that of a potential maximum depuration rate. However, for the Atlantic Croaker, this

relationship does not seem to be very strong (R2=0.3908, p<0.05). The relationship

becomes weaker when considering the M & C 43 and NOAA 18 congener groupings, and

BAFs calculated from dissolved water concentrations. This finding suggests that the

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Atlantic Croaker is more capable of equilibrating its intake and depuration rates at the

water and tissue concentrations found in this study than the Hardhead Catfish.

Figure 2. Relationship of lipid-normalized BAF to tissue concentration for

Hardhead Catfish (blue) and Atlantic Croaker (red). Lipid-normalized BAF

y = 210.37x + 2E+06

R² = 0.3908

p=0.0168

1.E+06

2.E+06

3.E+06

4.E+06

5.E+06

0 2 4 6 8 10 12

Cro

ak

er

BA

F (L

/kg

lip

id)

Tissue concentration (µg/g lipid)

y = 532.99x + 44127

R² = 0.8027

p=7.54E-09

5.00E+05

5.50E+06

1.05E+07

1.55E+07

0 5 10 15 20 25 30

Ca

tfis

h B

AF

(L/k

g li

pid

)

Tissue concentration (µg/g lipid)

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calculated using total water concentration and all PCB congeners. (2 outliers

removed for Hardhead Catfish regression)

3.2.2 Water concentration

The plot of water concentration against lipid-normalized BAF for Hardhead

Catfish and Atlantic Croaker is shown in Figure 3. No significant relationship was found

between the lipid-normalized BAF and dissolved water concentration for Hardhead

Catfish (R2=0.0963-0.1405, p>0.05) or Atlantic Croaker (R2=0.0064-0.0143, p>0.5). The

Hardhead Catfish data has a less random distribution than the Atlantic Croaker data, as

shown by the p-values and R2 values of the regressions. The results of the regressions

show that the BAF of the Hardhead Catfish seems to be more correlated to the water

concentration than the BAF of the Atlantic Croaker, which shows almost absolutely no

correlation with the water concentration, both total and dissolved phase. The calculation

of a BAF does not necessarily require equilibrium conditions, but the consistency of the

results would be improved if equilibrium had been reached. The fish specimens used in

this study do not remain in the spot they happened to be caught in, but are instead a

composite of the nearby waters. The specimens are exposed to a small, but still variable,

range of PCB concentrations in the HSC and its tributaries. The fact that the Atlantic

Croaker BAF is more random with respect to water concentration may be an indication of

how quickly it reaches equilibrium compared to the Hardhead Catfish. The intake and

depuration rates of the Atlantic Croaker may be faster, leading to a more accurate

representation of current PCB concentrations, rather than lifetime exposure another

species with slower intake and depuration rates may display.

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Figure 3. Relationship of lipid-normalized BAF with water concentration for Hardhead Catfish (blue) and Atlantic Croaker

(red). Lipid-normalized BAF calculated using respective water phase and all PCB congeners.

y = -1E+06x + 7E+06

R² = 0.0963

p=0.092

1.0E+06

6.0E+06

1.1E+07

1.6E+07

0 1 2 3 4

Ca

tfis

h B

AF

(L/k

g)

Total water concentration (ng/L)

y = -3E+06x + 1E+07

R² = 0.1405

p=0.061

5.00E+05

5.50E+06

1.05E+07

1.55E+07

2.05E+07

0 1 2 3

Ca

tfis

h B

AF

(L/k

g)

Dissolved water concentration (ng/L)

y = -165542x + 3E+06

R² = 0.0064

p=0.786

1.E+06

3.E+06

5.E+06

7.E+06

0 1 2 3C

roa

ke

r B

AF

(L/k

g)

Dissolved water concentration (ng/L)

y = 127837x + 2E+06

R² = 0.0143

p=0.683

1.E+06

2.E+06

3.E+06

4.E+06

0 1 2 3 4

Cro

ak

er

BA

F (L

/kg

)

Total water concentration (ng/L)

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3.3 Calculation of BAF for Hardhead Catfish and Atlantic Croaker

The bioaccumulation factor (BAF) can be calculated by two possible

deterministic methods, performing a linear regression on a plot of fish tissue

concentration against water concentration or dividing fish tissue concentration by water

concentration and analyzing the distribution. This study used both methods, the

regression method is shown in Table 2, a box and whisker plot of division method is

shown in Figure 4. The regression method showed that the use of congener groupings

McFarland and Clark 43 and NOAA 18 had no particular advantage over the use of all

congeners in the calculation of the BAF. The BAF for the congener groupings calculated

by the regression method slightly increased over that for all congeners. This would

suggest that the congeners selected for these groupings are indeed more bioaccumulative

than the suite of all 209 PCB congeners. The relationship of Atlantic Croaker lipid-

normalized tissue concentration and both total and dissolved phase concentration had a

strong linear correlation by the regression (R2=0.656-0.707, p<0.0005). The Hardhead

Catfish data for neither 2008 nor 2002-2003 data indicated the same relationship (p>0.05

for all regressions). The suspended phase water concentration surprisingly had a stronger

correlation with lipid-normalized fish tissue concentration than both total and dissolved

phase water concentration for Hardhead Catfish. The reason for this may be explained by

the typical diets of the two species. The mature Atlantic Croaker generally eats crabs,

shrimp and other fish like eels and minnows while the Hardhead Catfish has been found

to eat virtually anything, including algae, zooplankton, smaller Hardhead Catfish, mud,

and sand (Horst and Lane, 2006). This indicates that the Hardhead Catfish may actually

be more likely to consume and absorb PCBs that have adsorbed onto suspended particles.

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The BAF for the Atlantic Croaker was approximately double that of the Hardhead Catfish

for most regressions. However, by the box plot distribution method, the BAF of the

Hardhead Catfish was approximately triple that of the Atlantic Croaker. This is likely due

to the poor fit of the Hardhead Catfish data in the regression.

Several physical parameters, length, weight, and lipid content, of the species were

recorded during processing and analysis. These results are summarized in Table 3. On

average, the Atlantic Croaker had over four times the lipid content of the Hardhead

Catfish. On average, the Hardhead catfish was larger than the Atlantic Croaker, 40% by

length, 130% by weight.

The Hardhead Catfish was found to have a better correlation (R2=0.42, p<0.0005,

all congeners) between total water concentration and tissue concentration when tissue

concentration was not lipid-normalized. The Atlantic Croaker was found to have a similar

correlation (R2=0.43, p<0.005, all congeners). Considering the results of Table 2, we can

see that the goodness of fit for Hardhead Catfish worsened after lipid-normalization while

that for the Atlantic Croaker improved.

A t-test on the lipid-normalized BAF values for Hardhead Catfish in the 2002-

2003 and 2008 study reported a value of 0.472, showing no significant statistical

difference between the mean of the two data sets. Given the number of samples (31 in

2002-2003, 19 in 2008), these results, along with visual inspection of Figure 4, show that

the bioaccumulation behavior of the Hardhead Catfish was mostly unchanged from 2002-

2003 to 2008. Histograms of the two data sets also appear to be very similar, showing

little significant change in the BAF distribution from 2002-2003 to 2008.

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The values of the BAF found in this study agreed well with those found in related

literature. The range of lipid-normalized BAF calculated from dissolved water

concentrations was 8.95·105 to 5.82·107 and 1.33·106 to 6.09·106 for Hardhead Catfish

and Atlantic Croaker, respectively. On a logarithmic scale, this range is 5.95 to 7.76 and

6.12 to 6.78 for Hardhead Catfish and Atlantic Croaker, respectively. The EPA has

reported a log BAF, calculated on the same basis, range from 5.52 to 9.26 for Great

Lakes Trout and salmonids (USEPA, 1995). Another study on Great Lakes Trout

reported a log BAF range from 5.5 to 8.5, calculated on a dissolved water and wet weight

basis (Streets et al., 2006). A study on a Chinese e-waste site with elevated PCB water

concentration (mean concentration of 204 ng/L) reported a log BAF range of 1.2 to 8.4

(Wu et al., 2008). The Wu et al. 2008 study calculated BAF for several species including

carp, snails and water snakes and by individual PCB congeners. All of the BAFs

calculated for this study fall within the range of those found in the literature that

calculated BAFs for various species in various bodies of water.

Another study that created a small, artificial ecosystem contaminated with PCBs

within a glass and acrylic board cube (5.4 m3) found similar results of different BAFs for

different species (Lin et al., 2006). The Lin et al. 2006 study found that the five species

(three specimens of each) accumulated differing amounts of PCBs through the run of the

experiment. While the study performed by Lin et al. likely does not well represent a

natural environment, it does show that when different species are exposed to the same

conditions, they bioaccumulate different amounts of PCBs.

23

Table 2. Lipid-normalized BAF for Hardhead Catfish (2002-2003 and 2008 studies)

and Atlantic Croaker (only 2008 study) calculated by regression method with

corresponding goodness of fit and p-value.

Table 3. Physical parameters of fish samples from 2008 study.

Water Species R² p-value BAF (L/kg lipid) R² p-value BAF (L/kg lipid)

Total (All cong) Catfish 0.022 0.563 1.28E+06 0.102 0.17 1.02E+06

Total (M & C 43) Catfish 0.046 0.407 2.78E+06 0.114 0.068 2.38E+06

Total (NOAA 18) Catfish 0.025 0.542 2.32E+06 0.106 0.073 2.53E+06

Dissolved (All cong) Catfish 0.007 0.752 1.28E+06 0.042 0.329 1.03E+06

Dissolved (M & C 43) Catfish 0.034 0.475 3.48E+06 0.069 0.177 2.39E+06

Dissolved (NOAA 18) Catfish 0.013 0.661 2.53E+06 0.065 0.184 2.53E+06

Suspended (All cong) Catfish 0.064 0.325 6.09E+06 0.145 <0.05 2.48E+06

Suspended (M & C 43) Catfish 0.058 0.349 9.92E+06 0.233 <0.05 1.23E+07

Suspended (NOAA 18) Catfish 0.051 0.383 1.01E+07 0.220 <0.05 1.37E+07

Total (All cong) Croaker 0.696 <0.0005 2.65E+06

Total (M & C 43) Croaker 0.701 <0.0005 3.46E+06

Total (NOAA 18) Croaker 0.696 <0.0005 3.38E+06

Dissolved (All cong) Croaker 0.656 <0.0005 3.45E+06

Dissolved (M & C 43) Croaker 0.707 <0.0005 4.90E+06

Dissolved (NOAA 18) Croaker 0.669 <0.0005 4.45E+06

Suspended (All cong) Croaker 0.394 0.016 5.38E+06

Suspended (M & C 43) Croaker 0.454 0.008 7.81E+06

Suspended (NOAA 18) Croaker 0.451 0.008 8.09E+06

2002-20032008

24

Figure 4. Box plot of lipid-normalized BAF by species and time on a logarithmic

scale. BAF calculated by indicated water phase. All PCB congeners used. Outliers

are marked by diamonds. Extreme outliers marked by circles.

3.4 Comparison of species-specific BAF

The relationship of Hardhead Catfish BAF to Atlantic Croaker BAF is shown in

Figure 5. The lipid-normalized BAF was used for this regression, however an equivalent

representation would be the lipid-normalized tissue concentration of each species, since

the BAF was calculated simply by dividing the lipid-normalized tissue concentration by

the respective water phase concentration. The 2008 study had 13 common stations where

both species were collected and analyzed. There was definitely no correlation between

Hardhead Catfish BAF and Atlantic Croaker BAF. These common stations, as shown in

Figure 1, were generally part of Trinity Bay or a nearby section of the HSC.

The reason for the difference in the BAF in the two species likely occurs due to

the variation in habitat and life cycle. Atlantic Croaker is usually found in estuaries or

offshore water while the Hardhead Catfish can be found both in nearshore waters and

5.E+05

5.E+06

5.E+07

2002 Catfish

Total

2008 Catfish

Total

2008 Croaker

Total

2002 Catfish

Dissolved

2008 Catfish

Dissolved

2008 Croaker

Dissolved

BA

F (L

/kg

lip

id)

25

occasionally in freshwater, as seen by our finding of Hardhead Catfish in non-tidal

bayous (Horst and Lane, 2006). The concentrations found at stations in Trinity Bay were

generally lower than those found further up the HSC, meaning the Atlantic Croaker may

not be exposed to as high of PCB concentrations. The main reason for the deviation likely

occurs as a result of the life cycle of the species. The Atlantic Croaker generally does not

survive past 4 or 5 years, while the average life span for the Hardhead Catfish is 23 years

(Horst and Lane, 2006). For this reason, the Hardhead Catfish is likely more

representative of historical concentrations of PCBs than the Atlantic Croaker, which

reflects better on the current concentrations.

26

Figure 5. Relationship of lipid-normalized BAF calculated for Hardhead Catfish

and Atlantic Croaker from 13 common sites in 2008 study. Top plot used BAF

calculated from total water concentration, bottom plot used BAF calculated from

dissolved water concentration. All PCB congeners used.

y = 0.0056x + 2E+06

R² = 0.0029

p=0.862

1.E+06

2.E+06

3.E+06

4.E+06

1.0E+06 1.1E+07 2.1E+07 3.1E+07

Cro

ak

er

BA

F (L

/kg

lip

id)

Catfish BAF (L/kg lipid)

y = 0.0266x + 3E+06

R² = 0.0835

p=0.338

1.E+06

3.E+06

5.E+06

1.0E+06 2.1E+07 4.1E+07 6.1E+07

Cro

ak

er

BA

F (L

/kg

lip

id)

Catfish BAF (L/kg lipid)

27

4. Conclusions

Regressions of water and fish tissue data found that congener groupings

established by NOAA and McFarland and Clarke may be more bioaccumulative in

comparison to the suite of 209 PCB congeners. The bioaccumulation factor (BAF) for

PCBs was found to behave differently for the Hardhead Catfish and Atlantic Croaker.

The BAF distribution for Hardhead Catfish did not significantly change from 2002-2003

to 2008. The lack of correlation between the BAF or lipid-normalized tissue

concentration for each species at common sites suggests that the mechanism of

bioaccumulation differs by species. Due to differences between species, including diet,

intake, depuration and metabolism rates, length, weight and lipid content, a simple linear

deterministic model cannot predict a BAF for all fish species. The BAF calculated for a

species may also vary by region, such as a specific river or bay, due to potential changes

in the species’ overall behavior. On this basis, it would be most appropriate to determine

a region and species-specific BAF for bioaccumulative chemicals, including PCBs.

Acknowledgements

The research study described herein was sponsored by the National Science

Foundation under the Award No. EEC-0649163. The opinions expressed in this study are

those of the authors and do not necessarily reflect the views of the sponsor.

I am glad to have been under the guidance of Dr. Hanadi Rifai and Nathan

Howell. It has also been a pleasure to work with this group both in the office and the

field: Yaa Amoah, Anu Desai, Matt Feaga, Lisa Grecho, Emil Helfer, Becky Jimenez,

28

Divagar Lakshmanan, Jenni McFarland, Maria Modelska, Norma Moreno, Stephen Ray,

Scott Rauschhuber, Zack Van Brunt and Sharon Wells.

29

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