Modelling to derive guideline concentrations for organic contaminants in soils Swedish experiences...
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Transcript of Modelling to derive guideline concentrations for organic contaminants in soils Swedish experiences...
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