Modelling to derive guideline concentrations for organic

contaminants in soils

Swedish experiences

Mark ElertKemakta Konsult AB

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

Soil remediation in Sweden

National program for identification of sites

80 000+ 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

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

RISK

Background SOIL CONCENTRATION

No actionFurther investigation

and possible remediationRemediationnecessary

Trigger values

Negligiblerisk

Warning riskSignificant

risk

Intervention values

Long termobjectives

Targetvalues

ACTION

1997NV 4638 Generic guidelines. Principals and guidance for use

2005DRAFT VERSION July 2005 Guidance document

2008New Guidance document for risk assessment will be published.

1997NV 4639 Development of generic guideline values. Model and data used for generic guideline values for contaminated soils in Sweden

2005DRAFT VERSION July 2005 Model for soil guidelines

2008New document describing methodology and Excel-based model for soil guidance will be published

History of Swedish guidelines

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 substancesLong term risks considered

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

occurEstimation of concentrations in fish, but not integrated in soil criteria

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

Exposure pathways

Soil intake Dermal contact Inhalation of

dust Inhalation of

vapours Intake of well

water Intake of plants

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]

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

C

1 +

C

1

C

1+

C

1

C

1+

C

11

= C

plantswatervapourdustdermalsoil

health

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

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)

”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

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

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 – 150 000 Genotoxic. Toxic equivalent factor TEF 0.0005 – 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 200 000 – 3 000 000 Genotoxic. TEF: 0.005 – 1.1

Distribution of PAH in typical samples

Fördelning av PAH i Grupp 2

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6

pyren

fluoranten

antracen

fenantren

fluoren

Fördelning av PAH i Grupp 1

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6

acenaften

acenaftylen

naftalen

Fördelning av PAH i Grupp 3

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6

indeno(123cd)pyren

benso(ghi)perylen

dibens(ah)antracen

bens(a)pyren

bens(k)fluoranten

bens(b)fluoranten

krysen

bens(a)antracen

PAH L PAH M

PAH H

Nr TypeSample

s

1 Gasworks 4

2 Gasworks 82

3 Excavated soil 3

4 Cresote 2250

5 Cresote (1-40 mg/kg) 1130

6 Cresote 19

Effektivt TEF för grupperi PAH-prov

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Andel av prover

Su

mm

a (H

alt*

TE

F)/

Su

mm

a H

alt

Kreosotimpregnering Grupp 2

Kreosotimpregnering Grupp 3

Lyftkranen Grupp 2

Lyftkranen Grupp 3

Gasverk Grupp 2

Gasverk Grupp 3

Fyllning Grupp 2

Fyllning Grupp 3

Bensinstationer Grupp2

Bensinstationer Grupp3

Grundvatten Grupp 2

Grundvatten Grupp 3

Distribution of effective TEF

PAH H Most samples have

TEF = 0,2

PAH M Most samples have

TEF = 0,02

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

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

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

Direkta YtvattenGrundvatten

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)

1E-01

1E+00

1E+01

1E+02

1E+03

1E+04

1E+05

1E+06

1E+07

1E+00 1E+01 1E+02 1E+03 1E+04 1E+05 1E+06 1E+07 1E+08

Koc (l/kg)

Cto

t/Cp

or

(l/k

g)

DOC (kg/l) = 0

DOC (kg/l) = 1E-06

DOC (kg/l) = 3E-06

DOC (kg/l) = 1E-05

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

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

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?

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

Guidelines for petroleum related pollutants in groundwater Exposure pathways for groundwater

Surface water Wetlands

Well

Drinking water

IrrigationEvaporation

Oil

Intrusion into buildings

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