1. Kemakta Konsult AB www.Kemakta.se
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. Background SOIL CONCENTRATION
RISK
Background SOIL CONCENTRATION
No action
Further investigation
and possible remediation
Remediation
necessary
Trigger
values
Negligible
risk
Warning risk
Significant
Intervention
Long term
objectives
Target
ACTION

6. History of Swedish guidelines
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.
1997
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

7. What is protected? Soil environment Groundwater Surface waters
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
Human health
Direct contact with soil
Spreading via vapour, plants and groundwater
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 Age groups
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
Kemakta Konsult AB
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: Medium 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 L
PAH M
PAH H Nr
Type
Samples 1
Gasworks 4 2 82 3
Excavated soil
Cresote
2250 5
Cresote (1-40 mg/kg)
1130 6 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 Organic substances Empirical uptake factors
Model based on TGD and RIVM work:
Uptake in root,
Translocation to above ground parts
Uptake and release between leaf surfaces and ambient air
for dioxins and PCB

22. Leaching of contaminants
Kemakta Konsult AB
Leaching of contaminants
Grundvatten
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

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