Case Study 1

Application of different tools:

RBCA Tool Kit and APIDSS

Site locationSite location

Site mapSite mapSite mapSite map

Hazard assessment:Hazard assessment:Site investigationSite investigation

Hazard assessment:Hazard assessment:Site investigationSite investigation

Reconstruction of the site industrial Reconstruction of the site industrial history:history: location of old plants;location of old plants;processes and technologies utilized;processes and technologies utilized; wastes location and management.wastes location and management.

May affect sampling strategy and, consequently, the input data and the site conceptual model

Site investigation:Site investigation:Sampling strategySampling strategySite investigation:Site investigation:Sampling strategySampling strategyThe common question “Where and how many samples may be representative of site contamination ?” depends: on the horizontal and vertical distribution

of contaminants; on soil matrix nature.

The common question “Where and how many samples may be representative of site contamination ?” depends: on the horizontal and vertical distribution

of contaminants; on soil matrix nature.

Site investigation:Site investigation:Sampling strategySampling strategySite investigation:Site investigation:Sampling strategySampling strategyIt is problematic to establish general It is problematic to establish general rules and it is often appropriate to rules and it is often appropriate to follow practical site-specific indication.follow practical site-specific indication.

A statistical approach can be very A statistical approach can be very useful to quantify useful to quantify uncertainties uncertainties even even though it can lead to costly sampling though it can lead to costly sampling designdesign..

Data collection:Data collection:Chemical analysesChemical analyses Data collection:Data collection:Chemical analysesChemical analysesChoice of the most appropriate analytical Choice of the most appropriate analytical method depends on the detection limit that method depends on the detection limit that will meet the concentration level of concern. will meet the concentration level of concern. In R.A. both sensitive and selective analysis In R.A. both sensitive and selective analysis are required are required (many chemicals show toxicity (many chemicals show toxicity

effects even at very low concentrations)effects even at very low concentrations) since since both toxicity assessment and risk evaluation both toxicity assessment and risk evaluation are carried out for each CoC.are carried out for each CoC.

Site investigationSite investigationhidrogeologyhidrogeologySite investigationSite investigationhidrogeologyhidrogeologyActual direction of contaminant plume Actual direction of contaminant plume during pumping period from nearby during pumping period from nearby wells(1958 - 1978).wells(1958 - 1978).

Pumping from industrial wells Pumping from industrial wells produced local deviations of phreatic produced local deviations of phreatic and semiconfined flows and hydraulic and semiconfined flows and hydraulic connections between aquifers.connections between aquifers.

Actual direction of contaminant plume Actual direction of contaminant plume during pumping period from nearby during pumping period from nearby wells(1958 - 1978).wells(1958 - 1978).

Pumping from industrial wells Pumping from industrial wells produced local deviations of phreatic produced local deviations of phreatic and semiconfined flows and hydraulic and semiconfined flows and hydraulic connections between aquifers.connections between aquifers.

R.A. inputR.A. input R.A. inputR.A. input

Quality and confidence of R.A. results Quality and confidence of R.A. results strictly depend from these data and from the strictly depend from these data and from the type of algorithms used for risk evaluation.type of algorithms used for risk evaluation.

Different assessment levels (tiers) can Different assessment levels (tiers) can reduce uncertainties, moving from max. reduce uncertainties, moving from max. conservative assumptions to more site-conservative assumptions to more site-specific and accurate investigations.specific and accurate investigations.

RBCA Tool KitRBCA Tool KitRBCA Tool KitRBCA Tool Kit

To compare RBCA with API-DSS, the same To compare RBCA with API-DSS, the same conceptual model and input parameters conceptual model and input parameters were used, except for input concentrations were used, except for input concentrations of CoCs that were derived from different of CoCs that were derived from different statistical calculations. statistical calculations.

RBCA allows to calculate both risk to human RBCA allows to calculate both risk to human health and site-specific remediation targets.health and site-specific remediation targets.

API-DSSAPI-DSSAPI-DSSAPI-DSS Doesn’t directly calculate SSTLs, but uses fate & Doesn’t directly calculate SSTLs, but uses fate &

transport models for saturated and unsaturated transport models for saturated and unsaturated zone contaminant migration simulation.zone contaminant migration simulation.

It estimates a time-dependent CoC concentration It estimates a time-dependent CoC concentration reaching the receptor and max values are used reaching the receptor and max values are used by the risk and HI calculation module.by the risk and HI calculation module.

The model by means of a MonteCarlo algorithm The model by means of a MonteCarlo algorithm performs probabilistic F&T and Risk estimation, performs probabilistic F&T and Risk estimation, allowing to quantify uncertainties.allowing to quantify uncertainties.

Flow diagram of site Flow diagram of site conceptual modelconceptual model

Flow diagram of site Flow diagram of site conceptual modelconceptual model

Source Migration pathways Exposure points Targets

Soil

Atmospheric Dermal contact Commercial

suspension & & ingestion activities

dispersion workers/employees

Atmospheric

volatilisation & Air Remediation/

POLLUTED dispersion Particulate & Construction

SOILS vapours workers

inhalation

Resident people

Leaching & Groundwaters not connected

groundwater Drinkable use with public

transport water network

Third uncertainty Third uncertainty (Chemicals of concern, (Chemicals of concern, genericgeneric))

Third uncertainty Third uncertainty (Chemicals of concern, (Chemicals of concern, genericgeneric))

The selected CoCs were the same for The selected CoCs were the same for the two applied R.A. models.the two applied R.A. models.

The choice of a restricted number of The choice of a restricted number of pollutants may be an underestimation pollutants may be an underestimation of total risk, and this might represent of total risk, and this might represent another uncertaintyanother uncertainty..

Fourth uncertaintyFourth uncertaintyFourth uncertaintyFourth uncertainty

Toxicological and chemical-physical data Toxicological and chemical-physical data used for R.A. need to be continuously used for R.A. need to be continuously updated. updated.

To avoid uncertainties related to old data To avoid uncertainties related to old data several data bases (IRIS, HEAST, WHO, several data bases (IRIS, HEAST, WHO, NIOSH, etc.) can be used. One of the main NIOSH, etc.) can be used. One of the main problem is the estimation soil-water problem is the estimation soil-water distribution coeff. (Kd) of heavy metals. distribution coeff. (Kd) of heavy metals.

R.A. input concentrationsR.A. input concentrationsR.A. input concentrationsR.A. input concentrations

Pollutants spatial distribution was Pollutants spatial distribution was represented by kriging interpolation represented by kriging interpolation contour plots. The UCL (95%) of the contour plots. The UCL (95%) of the mean value of log-normal distribution, mean value of log-normal distribution, or max measured concentrations (in or max measured concentrations (in case of few available data) were case of few available data) were retained as representative source retained as representative source concentrations. concentrations.

Isoline map of Isoline map of lead lead

concentration concentration in surface soil in surface soil (<1,5 m deep) (<1,5 m deep) of site area. of site area.

Isoline map of Isoline map of lead lead

concentration concentration in surface soil in surface soil (<1,5 m deep) (<1,5 m deep) of site area. of site area.

584620m 584660m 584700m 584740m 584780m

9688

80m

9689

20m

9689

60m

9690

00m

9690

40m

0

500

50000

300000

notinterpolatedarea

mg/kg d.w.

100

1000

100000

Estimated “sources” for

API-DSS

Estimated “sources” for

API-DSS

Pb content in estimated “sources”for API-DSS

Pb content in estimated “sources”for API-DSS

Pb Surface soil<1m Subsurface

Zone n. Samples conc. n. Samples conc. max (mg/kg) max (mg/kg)

A 2 339 4 36C 3 30 4 40D 3 344 3 37E 2 2700 3 179F 1 30 1 23G 13 29000 11 346I 3 65 7 38L 9 594830 7 2105M 5 195000 2 36N 3 113 5 398O 4 6536 2 1080P 4 40000 6 22500Q 2 42R 5 14600 3 12700S 1 280 1 66T 3 1709 6 8056

Chemicals and Site main features

Chemicals and Site main features

Main chem-phys. characters of COCs are:Main chem-phys. characters of COCs are: solubility, Henry’s law constant, water diff., airsolubility, Henry’s law constant, water diff., air

diff., Kd (inorganics), Koc (organics);diff., Kd (inorganics), Koc (organics); data from updated databases.data from updated databases.

Hydrogeological model of the siteHydrogeological model of the site

RBCA vs. API-DSS resultsRBCA vs. API-DSS resultsSubstance Input conc. SSTL Input conc. SSTL Emilia Rom.

RBCA RBCA API-DSS API-DSS region limits (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg)

Benzene 2,2 E-2 4,4 E-2 2,0 E-2 0,02 5

Benzo(b)fluorantene 9,2 E-1 1,8 7,2 2 10

Benzo(a)antracene 1,4 1,9 4,8 2 10

Benzo(a)pyrene 9,6 E-1 1,9 E-1 7 2,0 E-1 10

Crysene 1,8 2,21 8,9 1 n.f.

Dibenzo(a,h)antracene 8,3 E-2 1,9 E-1 2,4 2,0 E-1 10

Ethylbenzene 2,8 E-2 9,1 E+1 1,0 E-1 1,0 E-1 50

Indeno(1,2,3,c,d)pyrene 8,3 E-1 1,9 7,1 2 10

Lead 3,4 E+4 9,59 E+2 1,2 E+5 1,7 E+3 1000

Naphtalene 7,2 E-1 29 2,5 2,5 50

Tetraethyl Lead 5,8 2,6 E-4 463 6,0 E-3 n.f.

Toluene 4,1 E-1 58 1,5 1,5 30

Trichloroethylene 2,1 E-2 1,1 E-1 0,6 0,6 10

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Lisbon, 24-25 June 1999 International Conference on “ Investigation Methods on Soil Contamination” 22

Main uncertainties Main uncertainties

Uncertainties in modeling :Uncertainties in modeling : Affect the accuracy of R.A.Affect the accuracy of R.A. Require a model validation (often not feasible Require a model validation (often not feasible

because of the predicting nature of R.A.)because of the predicting nature of R.A.) Suggest a strictly conservative approachSuggest a strictly conservative approach

Uncertainties in input dataUncertainties in input data Can be quantified by probabilistic approachesCan be quantified by probabilistic approaches

General conclusions General conclusions

Characterisation of a contaminated site should provide Characterisation of a contaminated site should provide data necessary for exposure analysis and provide an data necessary for exposure analysis and provide an assessment of associated uncertaintiesassessment of associated uncertainties

Geostatistical techniques allows to infer much more Geostatistical techniques allows to infer much more information from site and analytical data, and to quantify information from site and analytical data, and to quantify the uncertainties of estimated valuesthe uncertainties of estimated values

In this case R.A. provides a result in favour of remedial actions Quite similar results for most CoC obtained by the two model

lead to the conclusion that even if some lack of information exist (about site-specific parameters or features) a deeper level of risk calculation requiring more costs and time may be not useful

CASE STUDY 2

ROME