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RISK ASSESSMENT
Petroleum hydrocarbons
ReLASC – NICOLE Seminar, 31.5.-2.6.2015
Lima, Peru
Jussi Reinikainen, Senior Advisor, Finnish Environment Institute
Vahanen Environment Oy / Vesa Kippola
● Risk assessment (RA) – what, why and how?
● Key elements in RA for petroleum hydrocarbons
● Conclusions
2
CONTENTS OF PRESENTATION
EU expert support financed by TAIEF
Environmental Technical Assistance
and Information Exchange Facility (ENV-TAIEF)
This project is financed by the European Union
FINLAND
3
● Nordic country with 5,5 million
people
● 200 000 lakes
● Woods more than anyone can
count
● Anything else?
4 aamulehdenblogit.ning.com
5 www.skysports.com
6 nokiamobilephonedetail.blogspot.com
SOLD
nokiamobilephonedetail.blogspot.com
7 angrybirds.wikia.com
8 yle.fi
9
● Both scientific and regulative procedure/tool
○ Decision-making: Are risks big enough to warrant actions?
● Based on source–pathway–receptor linkage
○ Always site-specific
● Targets and desired level of protection depend on regulatory demands
○ Risk assessment includes political elements, not only toxicological aspects
10
RISK ASSESSMENT
Source Pathway Receptor
Contaminants in
soil and
groundwater
Direct exposure,
transport via water
and air
Effect on quality of the
environment, human
health and biota
11
CONCEPTUAL MODEL
TARGETS AND GOALS
RISK ESTIMATES
RISK MANAGEMENT
DECISION
SITE HISTORY
RISK MANAGEMENT
ACTIONS
PROCEDURE
RISK IDENTIFICATION - CONCEPTUAL SITE MODEL
● Sources of contamination ○ E.g. gasoline / diesel spill
○ Contaminants of concern
● Receptors ○ People
○ Groundwater
○ Surface water
○ Biota
● Multiple routes and pathways for contaminant migration and exposure
○ Contaminant properties and source location
○ Land use and site conditions
Outlining content and targets of further assessment
ASSESSMENT OF EXPOSURE, TRANSPORT AND EFFECTS
● Clear objectives ○ Definition of protection
goals and ”decision units” (e.g. exposure areas, main sources for migration, receptors)
● Risk estimates based on multiple lines of evidence
○ Representative sampling (cf. ”decision units”)
○ Calculations based on sampling results
○ Other measurements
Assessing actual risks with defined decision units or comparing soil concentrations with generic soil standards?
EXAMPLE OF OBJECTIVES FROM FINLAND - WHAT DO
WE WANT TO PROTECT?
● Local soil ecosystem is often NOT our primary protection target...
● ...yet we often end up using soil ecotoxicity-based soil guideline values (SGV) as remediation targets ○ e.g. SGVeco for Zn and Cu 250 and 150 mg/kg, while SGVhealth > 10 000 mg/kg
● In addition, we most often remediate by dig and dump...
→ So, are we really protecting local soil ecosystem?
→ Is this justified risk-based decision-making…?
14
Kimmo Järvinen
Petri Heino
● Crude oil and petroleum products complex mixtures of hydrocarbons ○ Light Non-Aqueous-Phase Liquids (LNAPL) -> less dense than water
○ Different products -> different hydrocarbons, including additives (e.g. MTBE)
○ Different substances -> variable environmental behaviour and toxicity
○ Weathering (ageing) -> changes in composition in time and space
→ Source zone has to be well characterized and understood
→ Risk assessment cannot be based on content of total petroleum hydrocarbon (TPH) only
15
PETROLEUM HYDROCARBONS
Brewer et al. 2013
Int J Environ Res Public Health 2013, 10(6): 2441
STARTING POINTS 1/2
16
NAPL
Residual phase
NAPL
Free phase
Dissolved phase
(plume)
Newell et al. 1995
● Original emission ○ Physical properites of NAPL (e.g. viscosity, density) dictate transport alongside
soil properties
● LNAPL contamination in soil ○ Controlled by petroleum product, original release and soil type/heterogeneity
○ Properties of individual hydrocarbons dictate partioning and transport from LNAPL
● Weathering reduces LNAPL mass and risks in time o Biodegradation, volatilization, leaching, soprtion etc.
STARTING POINTS 2/2
17
● Residual phase LNAPL
o Trapped in soil pores; immobile and cannot be physically recovered (pumped
out)
o Can also exist in saturated zone (fluctuation of groundwater level)
● Free phase LNAPL
o Exceeds retain capacity of soil; mobile and can be pumped out
o Not always easy to locate/measure directly
Maximum concentrations in residual phase
Fine sand and silt:
- gasoline: 5 000-10 000 mg/kg
- heavy fuel oil: 30 000 – 50 000 mg/kg
Gravel and coarse sand:
- about 10 times less
→ Occurence and composition of LNAPL affects both risk assessment and risk management
● Whole product approach ○ Based on products (e.g. gasoline, diesel, jet fuel)
○ Applies only to fresh emissions (no weathering) with one and well known source product
● Indicator compound approach ○ Based on most harmful and well known individual compounds, e.g. BTEX,
MTBE, PAH
○ May not be enough when share of indicator compounds in actual petroleum mixture is low
● Fraction approach ○ Assessment based on specific aliphatic and aromatic fractions, i.e. groups of
compounds with (presumably) similar properties (e.g. Total Petroleum Hydrocarbon Criteria Working Group, 1997)
○ Potential caricinogenic compounds need to be evaluated separately (e.g. benzene, certain PAHs)
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APPROACHES FOR RISK ASSESSMENT OF
PETROLEUM CONTAMINATION
EXCLUDING RISKS DUE TO MIGRATION OF MOBILE NAPL OR COLLOIDS
→ Indicator compound and fraction approaches usually applied together on contaminated land
● E.g. in Finland guideline values given only for C5-10, >C10-21, >C21-40
→ Site-specific assessment based on fraction and/or indicator compound approach always needed
19
VARIATION IN CONTAMINANT PROPERTIES - FATE
AND TRANSPORT
Fraction M
[g/mol]
S (+10oC)
[mg/l]
Vp (+10oC)
[Pa]
H (+10oC)
[-]
logKoc
[l/kg]
logKow
[-]
Aliphatic
EC5-EC6 81 28 50007 47 2,9 3,52
>EC6-EC8 100 4,2 8610 50 3,6 3,60
>EC8-EC10 130 0,325 821 55 4,5 3,69
>EC10-EC12 160 0,0261 79 60 5,4 3,76
>EC12-EC16 200 0,00059 3,55 69 6,7 3,85
>EC16-EC35 270 0,000000999 0,172 87 8,8 3,97
Aromatic*
>EC8-EC10 120 65 821 0,39 3,2 3,55
>EC10-EC12 130 25 79 0,13 3,4 3,58
>EC12-EC16 150 5,8 3,55 0,028 3,7 3,61
>EC16-EC21 19 0,65 0,172 0,0019 4,2 3,66
>EC21-EC35 240 0,0066 0,000017 0,000017 5,1 3,74
* Aromatic fraction > EC6-EC8 includes only benzene and toluene that are assessed separately
Gustafson ym. 1997; Otte ym. 2001
VARIATION IN CONTAMINANT PROPERTIES -
HEALTH RISKS
20
Fraction TDI
g/kg/d
TCA
g/m3
WHO drinking water (2008)
g/l
Aliphatic
>EC5-EC8 2000 18 400 1500
>EC8-EC16 100 1 000 300
>EC16-EC35 2000 NA 300
Aromatic
>EC5-EC8*
Benzene (10-5)
200
3,3
400
1,7
1 (benzene)
700 (toluene)
>EC8-EC16 40 200 90
300 (ethylbenzene), 500 (xylenes)
>EC16-EC35
B(a)P (10-5)
30
0,05
NA 90
0,7
* Aromatic fraction > EC6-EC8 includes only benzene and toluene that are assessed separately
TPHWG ,1997; WHO 2010, 2011
→ Genotoxic carcinogens have to be assessed separately!
→ Check you literature data!
Brewer et al. 2013
Int J Environ Res Public Health 2013, 10(6): 2441
● Ecotoxicity of petroleum hydrocarbons in general is relatively low ○ Only more soluble compounds are (bio)available enough
• 100-500 mg/kg (>C5-C10) and >C10-C16: 500-2000 mg/kg protective for most soil ecosystems, but even much higher levels can be acceptable
○ Significant bioaccumalation is not expected under most conditions
○ Animals on higher trophic levels readily metabolize hydrocarbons
● Ecotoxicity of petroleum contaminated soil reduces in time ○ Weathering ->biodegradation, volatilization and leaching of available
fraction
● Ecological risks depend on site conditions and depth of contamination ○ ”Bioactive” surface soil and root zone
○ Migration to surface water; NOTE: potential mobile NAPL!
● Adverse physical effects may occur ○ Staining due to high concentrations in top soil
○ Free product or ”oil films” on surface of water bodies
○ Coatings on sediments
21
ASPECTS OF ECOLOGICAL RISK ASSESSMENT
OTHER KEY CONSIDERATIONS
22
● Effective solubility and saturated vapor pressure in petroleum mixture o Always less than theoretical values for single compounds (mole fraction)
o For most aliphatic compounds(>C10) effective solubility less than typical
water standards
● Biodegradation well demonstrated
o Both in dissolved and vapor phase
o Most rapid under aerobic conditions
o Still needs to be confirmed on site!
● Odor issues and aesthetic aspects need to be considered
o Difficult to set justified concentration thresholds based on such effects
o Direct remediation of top soil may be reasonable especially in sensitive
areas or nearby surface water bodies
o Removal of free phase NAPL usually meaningful (when technically and
economically feasable)
CALCULATIONS/MODELING
23
● Simple quantitative tools and default exposure parameters available
o E.g. based on RBCA equations (ASTM)
o Requires knowledge on site conditions, contaminants and theory
o Calculations need to match site conditions and objectives (e.g. representative
concentrations in exposure areas)
o May not be directly applicable to NAPL (including residual phase)
o May not take weathering and biodegradation into account (conservativeness)
o Literature values for toxicity and fate/transport vary and are updated
● Risk assessment should NEVER be based on modeling only
o Validation with representative measurements and information on site history
(e.g. theoretical vs. observed transport)
o Many ”risks” (= targets of RA) can be measured directly without modeling
Variation in Tier 1 cleanup levels (survey of 50
U.S. States and Canada; http://www.itrcweb.org)
TPH 50…4 100 mg/kg
Gasoline 3.1…1 500 mg/kg
Diesel 2.7…5 000 mg/kg
Residual fuels 99…10 000 mg/kg
CONCLUSIONS - MAJOR RISK FACTORS AND
DRIVERS
24
● Groundwater contamination
o BTEX, MTBE, naphtalene and other aromatic compounds/fractions < C21
● Health risks mainly due to indoor air and drinking water exposure
o Benzene, naphtalene and aromatic compounds/fractions < C12
o Direct exposure to top soil relevant mainly for carcinogenic PAHs
o Outdoor air exposure may be relevant for large scale contamination
● Mass flux to groundwater mostly from NAPL source below and to (indoor)
air from NAPL source above groundwater table
o Dimensions and composition of source zone/NAPL important
● Ecological risks mainly due to high concentrations in surface soil and/or
migration to nearby surface water bodies (including mobile NAPL)
● Odor and aesthetic aspects need to be taken into account especially for
top soil and sensitive landuse
REGULATORY REQUIREMENTS MAY DIFFER FROM
TOXICOLOGICAL RISKS
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● Removal of mobile NAPL
● Shrinking (or stable) groundwater plume
● No off-site migration
● Generic quality standards for groundwater, surface water or air
● Odor and taste thresholds in drinking water
Removal of
mobile NAPL
SUMMARY
26
● Setting clear objectives for risk assessment first priority
● Characterizing and understanding contamination source (NAPL) very important
● RA should be based on indicator compounds and specific hydrocarbon fractions by using multiple lines of evidence and representative sampling
● Wheathering / biodegradation may reduce risks significantly
● Groundwater contamination and indoor air exposure often major risk factors in addition to mobile NAPL and high concentrations in top soil
● Regulatory requirements and aesthetic aspects may warrant additional actions
→ Reliable risk assessment promotes justified decisions and reasonable (=sustainable) risk management!
MUCHAS GRACIAS -
THANK YOU!
27
Environmental Technical Assistance
and Information Exchange Facility (ENV-TAIEF)
This project is financed by the European Union
Thank you also to TAIEF!
