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Modelling to derive guideline concentrations for organic contaminants in soils Swedish experiences Mark Elert Kemakta Konsult AB.

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Presentation on theme: "Modelling to derive guideline concentrations for organic contaminants in soils Swedish experiences Mark Elert Kemakta Konsult AB."— Presentation transcript:

1 Modelling to derive guideline concentrations for organic contaminants in soils Swedish experiences Mark Elert Kemakta Konsult AB

2 Content Soil remediation in Sweden Overview of the Swedish system for soil guidelines Recent (ongoing) revision of the guidelines Special procedures for organic contaminants Problem areas Plans for the future

3 Soil remediation in Sweden National program for identification of sites sites Mining and metallurgy Heavy metals Wood treatment Arsenic and PAH Dioxin State funding for remediation of old sins Many rural sites New housing In the main cities Efforts to increase pressure on industry to remediate

4 Swedish guidelines for soil Values for when no risk for health and environment is expected Not legally binding Not to be used directly as remediation goals (although that is often the case) Protective for most sites in Sweden Over-protective for many sites Option to determine site-specific values Using same methodology as for generic criteria Other methods Generic methods and models largely based on European (Dutch) and US EPA models

5 RISK BackgroundSOIL CONCENTRATION No action Further investigation and possible remediation Remediation necessary Trigger values Negligible risk Warning risk Significant risk Intervention values Long term objectives Target values ACTION

6 1997 NV 4638 Generic guidelines. Principals and guidance for use 2005 DRAFT VERSION July 2005 Guidance document 2008 New Guidance document for risk assessment will be published NV 4639 Development of generic guideline values. Model and data used for generic guideline values for contaminated soils in Sweden 2005 DRAFT VERSION July 2005 Model for soil guidelines 2008 New document describing methodology and Excel- based model for soil guidance will be published History of Swedish guidelines

7 What is protected? Human health Direct contact with soil Spreading via vapour, plants and groundwater Soil environment Effects on plants and animals within the contaminated site Groundwater For drinking water As a resource Surface waters Effects on aquatic life No increase in concentration of persistent substances Long term risks considered

8 Main changes in new version of Soil Criteria Model Excel based model: Basis for setting the generic guidelines For estimating site-specific guidelines Changed balance in assessment: Less conservative estimates of exposure More stringent limits for health effects and release New or improved models: transport of vapours to indoor and outdoor air Uptake of organic contaminants in plants Transport to groundwater Release of organics with dissolved organic carbon (DOC) Limits for when free-phase of organic pollutants can occur Estimation of concentrations in fish, but not integrated in soil criteria

9 Human health Models for exposure under generic conditions Conservative, but not unrealistic estimates of exposure Sensitive land use (KM) Less Sensitive land use (MKM) Age groups Children (0 – 6 yr) Adults (7 – 80 yr) Substances with threshold effects Most exposed group compared with Tolerable Daily Intake, TDI Genotoxic substances: Life-time (80 years) average exposure compared with intake corresponding to an added risk of 10 -5

10 Exposure pathways Soil intake Dermal contact Inhalation of dust Inhalation of vapours Intake of well water Intake of plants

11 Calculation of health risk based value C = corresponding concentration in soil: C = TRV / (EXP DF FF) TRV = toxicological reference value [ mg/kg body weight, day ] EXP = exposure to contact media [ kg/kg body weight, day ] FF = distribution in contact media [ conc i contact media/conc in soil) ] DF = dilution in contact media [ conc at contact point/ conc at source ]

12 Integration of exposure pathways Exposure from all pathways Only a part of the TDI can be come from the contaminated site Generally 50% Pb, Cd, Hg 20% Dioxin and PCB 10% Special consideration for substances giving acute health effects: Arsenic and cyanide

13 Protection soil environment Quantification of critical effects for an ecosystem : Serious risk to the environment = Serious risk to ecosystem functions If most of the species of organisms in the ecosystem are protected, the ecosystem functions will also be protected (Conversely, ecosystem functions are threatened if the species composition is seriously disturbed) Risk to the environment the probability that more than a certain fraction of the species i are harmed by contaminants Protection of species at the population level Data from ecotoxicological effects tests statistical distribution

14 Protection soil environment Species sensitivity distributions SSD Generic guidelines: Sensitive land use: Protection of 75% of species (NOEC-data) Less sensitive land use: Protection of 50% of species (NOEC-data) Safety factor method when only few data available NOEC or LOEC divided with safety factor (10 – 1000)

15 Special cases Bioaccumulating contaminants Toxic reference value (intake in mg/kg body weight) Exposure model with BCF, eg. soil, plant, herbivore, carnivore Process data (carbon and nutrient turnover, enzymes) As a check on SSD Integrated with other data into one SSD

16 Organic substances Chlorinated phenols Chlorinated benzenes Chlorinated aliphatics PCB and dioxins BTEX Aliphatic fractions (revised TPHCWG) Aromatic fractions (revised TPHCWG) PAH divided into three groups PAH L low molecular weight PAH M medium molecular weight PAH H high molecular weight Others MTBE

17 Groups of PAH Low molecular weight: Naphthalene, acenaphthylene, acenaphthene Relatively mobile: Koc < 5000 Non-genotoxic TDI Medium molecular weight : Fluorene, phenanthrene, anthracene, fluoranthene, pyrene Intermediate mobility Koc 5000 – Genotoxic. Toxic equivalent factor TEF – 0.05 High molecular weight : benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benz(a)pyrene, dibenzo(ah)anthracene, benzo(ghi)perylene, indeno(123cd)pyrene Low mobility Koc – Genotoxic. TEF: – 1.1

18 Distribution of PAH in typical samples PAH LPAH M PAH H NrTypeSamples 1Gasworks Excavated soil 3 4Cresote Cresote (1-40 mg/kg) Cresote 19

19 Distribution of effective TEF PAH H Most samples have TEF = 0,2 PAH M Most samples have TEF = 0,02

20 Transport of vapours Simplified Johnson- Ettinger model Diffusion of vapours in ground Leakage of soil air into building Turn over of air inside building Model for outdoor air Diffusion of vapours in soil Transfer to ambient air Dilution in mixing layer

21 Uptake by plants Metals Empirical uptake factors Organic substances Model based on TGD and RIVM work: Uptake in root, Translocation to above ground parts Uptake and release between leaf surfaces and ambient air Empirical uptake factors for dioxins and PCB

22 Leaching of contaminants Release of contaminants with through flowing water Enhanced leaching by mobile organic carbon (for organics) Constant source term Estimating leaching properties Equilibrium assumed (Kd-values) Metals – Conservative empirical values Organics estimated from water-octal distribution coefficients (Koc) and content of organic carbon in soil Grundvatten

23 The effect of mobile organic material Mobile organic material in soil Sorption on dissolved organic matter or very small organic particles Important for pollutants with very high Koc (log Koc > 4-5)

24 Contamination of well water Simple model that estimates the amount of dilution in the groundwater zone Sorption, degradation or evaporation not considered Protection also of groundwater resourced Criteria for groundwater 50% av drinking water guidelines Sensitive land use at site Less Sensitive land use 200 m from site

25 Protection of surface waters Protection of aquatic life in surface water recipients Dilution of release into a small stream (30 l/s) Criteria for surface waters: Metals and persistent organics Deviation from background/ambient levels Other contaminants 50% of effect based criteria Proposed EQS (EU, Sweden) Data from Canada, the Netherlands

26 Recognised problems Very soluble substances and DNPL Guidelines for groundwater more useful than for soil Volatile substances Assumption of infinite source not valid May lead to overly conservative values Petroleum hydrocarbons Suitable division into TPHCWG fractions Difficult to relate guidelines to different analytical methods Analysis methods for aromatics Persistent Organic Pollutants Background levels (exposure, in the environment) Local or large-scale problem?

27 Guidelines for other media No remediation oriented guidelines available: Groundwater Proposed values for petroleum related contaminants Sediments Surface waters Leads to use of criteria from other countries The Netherlands Canada USA

28 Guidelines for petroleum related pollutants in groundwater Exposure pathways for groundwater Surface water Wetlands Well Drinking water Irrigation Evaporation Oil Intrusion into buildings

29 Future New guidelines and soil criteria published in late autumn New guideline for risk assessment Continued work with updating guidelines and criteria Guidelines for other media

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