Introduction to Contaminated Sites PDF

INTRODUCTION TO CONTAMINATED SITES JENNY NORRMAN ACE146 CONTENT History - some (in-)famous examples Contaminated sites today Sources to contamination Risks and assessment of risks Site conditions, sampling and data evaluation Risk reduction and remediation technologies S...

INTRODUCTION TO CONTAMINATED SITES JENNY NORRMAN ACE146 CONTENT History - some (in-)famous examples Contaminated sites today Sources to contamination Risks and assessment of risks Site conditions, sampling and data evaluation Risk reduction and remediation technologies Some research at our group, MSc-thesis ACE146 - Introduction to contaminated sites 2 LOVE CANAL, NIAGARA FALLS, NEW YORK STATE Canal for hydroelectricity – never finished (1910) Used as municipal & chemical dumpsite, approx. 0.28 km2, Hooker chemical company (from 1940) - "caustics, alkalines, fatty acid and chlorinated hydrocarbons (manufacturing of dyes, perfumes, and solvents for rubber and synthetic resins) 1953 covered with earth and sold to School Board for 1$ with liability limitation clause, late 50ies: ~100 homes + 1 school built 1978 – high rainfall event – excessive leaching – State of emergency by Pres. Jimmy Carter Birth defects, anomalies such as enlarged feet, heads, hands, and legs, chromosome damages (benzene & dioxin) Remediation by removal and containment, ~400M$ during 21 years ACE146 - Introduction to contaminated sites 3  LOVE CANAL https://en.wikipedia.org/wiki/Love_Canal ACE146 - Introduction to contaminated sites 4 LEKKERKERK, NL Village near Rotterdam, ~6500 inhab. (1980) 8.9 hectares, residental area: Houses, bungalows, school, gymnasium Built in late 60:ies on ditches with waste (domestic, industrial) 1979 – soil pollution discovered – 1980 first soil remediation project in NL Toluene, xylene, possibly benzene, in groundwater and beneath houses Although no effects could be found among inhabitants, https://nl.wikipedia.org/wiki they were evacuated, dig & dump, pump & treat, ~85 M€ /Gifschandaal_Lekkerkerk ACE146 - Introduction to contaminated sites 5 BT KEMI – TECKOMATORP, SWEDEN Manufacturing of herbicides from 1965, phenoxy acids, dinoseb Secretly buried oil drums with organic pollutants Scandal culminating 1977 – the main building was blown up in 1979 – 40 years anniversary 1st remediation late 70:ies 2nd remediation in the 80:ies 3rd remediation: northern area in 2008 ACE146 - Introduction to contaminated sites 6 BT KEMI http://www.svalov.se/ovrigt/ga- direkt/bt-kemi-efterbehandling/in- english.html ACE146 - Introduction to contaminated sites 7 RESULT: INCREASING AWARENESS ABOUT ENVIRONMENTAL EFFECTS AND RESPONSIBLITIES Love Canal – Superfund (1980) Lekkerkerk – Soil Clean Interim Act (1983) BT Kemi – focusing event – establishment of concept of environmental crime ACE146 - Introduction to contaminated sites 8  European numbers in CONTAMINATED SITES - Swartjes, Section 1.1.2.1 INTERNATIONAL NUMBERS Potentially contaminated sites in Europe estimated to 2.5 million, with 342,000 confirmed to be contaminated (Panagos et al., 2013). 80,000 sites have been cleaned up during the last 30 years Potentially contaminated sites in the US 217,000, with 77,000 of those sites needing clean up (US EPA, 2004) China: lags behind, no formal process, budgeted $110 million for soil pollution over 5 years. The first national soil pollution survey (2014): 16% of the surveyed land (6.3 million km2) was contaminated beyond acceptable standards (Ma et al., 2018) Kabwe – old mining town in Zambia. Guardian, 2017 ACE146 - Introduction to contaminated sites 9 EXPENDITURES 35% of the remediation expenditures comes from public budgets even though most countries apply the polluter-pays principle Remediation measures: 60%; Site investigations: 40% Total annual management expenditures in Million € 2005 http://www.eea.europa.eu, Copyright EEA, Copenhagen, 2007 ACE146 - Introduction to contaminated sites 10  CONTAMINATED SITES IN SWEDEN IN NUMBERS About 80 000 potentially contaminated sites in Sweden, 1300 pose substantial risk. Only a fraction of these sites has been remediated, at an average cost of 40 million SEK One of the largest expenditures at the Swedish Ministry of Environment, with an annual expenditure of approximately 500 million SEK. Remediation is made regularly in exploitation projects. Total annual remediation cost in Sweden: 2-3 billion SEK. ACE146 - Introduction to contaminated sites 11  Very high risk High risk Moderate risk Low risk Not classified Potentially contaminated sites around Göteborg (map from 2016) EBH-kartan (lansstyrelsen.se) 12 ACE146 - Introduction to contaminated sites CONTAMINANT SOURCES Ref: http://soer.justice.tas.gov.au/2003/image/532/o-contaminated_sites-m.jpg ACE146 - Introduction to contaminated sites 13 THE MAIN SOURCES CAUSING SOIL CONTAMINATION IN EUROPE ( % OF THE NUMBER OF SITES WHERE PRELIMINARY INVESTIGATIONS HAVE BEEN COMPLETED) 2009 http://www.eea.europa.eu, Copyright EEA, Copenhagen, 2009 ACE146 - Introduction to contaminated sites 14 A BREAKDOWN OF THE INDUSTRIAL AND COMMERCIAL ACTIVITIES CAUSING SOIL CONTAMINATION (% OF THE NUMBER OF SITES FOR EACH BRANCH OF ACTIVITY) 2006 http://www.eea.europa.eu, Copyright EEA, Copenhagen, 2009 ACE146 - Introduction to contaminated sites 15 TYPES OF CONTAMINANTS Mineral oil and heavy metals are the most frequent contaminants found in soil 2006 Mineral oil and chlorinated hydrocarbons are the most frequent contaminants found in groundwater http://www.eea.europa.eu, Copyright EEA, Copenhagen, 2009 ACE146 - Introduction to contaminated sites 16 PFAS: PER- & POLYFLUOROALKYL SUBST. Large, complex group: > 10 000 identified subst. Synthetically produced and used in various products, e.g. fire-fighting foams and waterproofing agents. WIDELY distributed in the environment Extremely persistent, difficult to remediate as there are few available techniques Some have been shown to have adverse effects on humans and animals (e.g. PFOS, PFOA). ACE146 - Introduction to contaminated sites 17 Figure from: Evighetskemikalier: PFAS ACE146 - Introduction to contaminated sites 18 RISK ASSESSMENT How dangerous is this? Can we allow people to live here? Can we allow children to play here? Can we allow people to work here? Are ecosystems affected? Do we need to remediate? ACE146 - Introduction to contaminated sites 19  HOW CAN HUMANS BE EXPOSED TO CONTAMINANTS IN THE SOIL? Think about how contaminants in the soil can end up in humans (1 min) Discuss with your neighbour (2 min) Share your ideas with the rest of the class (2 min) ACE146 - Introduction to contaminated sites 20  Exposure pathways humans ACE146 - Introduction to contaminated sites 21 PRINCIPLE FOR RISK ASSESSMENT Source Receptor Landfills, Humans, contaminated ecosystems, waters, soil, waste etc. buildings release Pathway exposure soil, water, air ACE146 - Introduction to contaminated sites 22 SWEDISH EPA (2002): HAZARDASSESSMENT OF CERTAIN CHEMICAL SUSBTANCES Read more in Swartjes, Sections 1.1, 1.2, 1.3 ACE146 - Introduction to contaminated sites 23 COMPLEX SITES ACE146 - Introduction to contaminated sites 24 SAMPLING AND DATA EVALUATION ACE146 - Introduction to contaminated sites 25 COMPARISON OF SOME REPRESENTATIVE VALUE TO A GUIDELINE VALUE (SOIL QUAILITY STANDARD or a SOIL GUIDELINE VALUE) 01 Guideline value A. 05 s 0 UCL95 = m + t 95;n −1 ⋅ n 01 B. 05 0 0 50 100 150 200 250 RISK REDUCTION STRATEGIES Source barrier Air Protection barrier Risk- Surface water Risk - source object Groundwater Spreading barriers Exposure Source Spreading Recepient ACE146 - Introduction to contaminated sites 27 SOIL AND GROUNDWATER REMEDIATION Concentration techniques = concentrate contaminants before disposal, containment or destruction. Destruction techniques = destroys contaminants and alter them into less harmful products. Immobilization techniques = restrict contaminant movement and/or bioavailability. ACE146 - Introduction to contaminated sites 28 TERMINOLOGY REMEDIATION TECHNOLOGIES In situ = treatment of the contaminated media in the ground, always on site. Ex situ = implies excavation of the contaminated soil or pumping of the contaminated groundwater before treatment, either on site or off site ACE146 - Introduction to contaminated sites 29 REMEDIATION HAS POSITIVE OCH NEGATIVE EFFECTS! Reduced health risks Costly Reduced ecological risks Health risks to workers Increased property value Risks associated with transports Increased recreational value Noice Possibilities for new landuse Air emissions Less worry among the public Use of natural resources: Fossil energy Other non-renewable resources ACE146 - Introduction to contaminated sites 30  MOST COMMON REMEDIATION STRATEGY ”Dig and dump” Problems? Call for increasing the use of more innovative technologies ACE146 - Introduction to contaminated sites 31 WORK AT GEO IN RELATION TO CONTAMINATED SITES Decision support systems Risks, costs and benefits Sustainability assessments Statistical methods for data evaluation and sampling strategies Balancing costs and risks, e.g. value of information, remediation options Soil functions Efficiency and sustainability in remediation Circular handling of contaminated masses Gentle remediation options, circular land management and ecosystem services Master thesis? Take a look at Canvas, some suggestions are uploaded. Or contact jenny,[email protected] or any of the other teachers ACE146 - Introduction to contaminated sites 32 ACE146 REMEDIATION LARS ROSÉN (THANKS TO PETRA BRINKHOFF AND JENNY NORRMAN) GEOLOGY AND GEOTECHNICS ARCHITECTURE AND CIVIL ENGINEERING CHALMERS UNIVERSITY OF TECHNOLOGY LEARNING OUTCOMES Understand and describe the design and functionality of commonly used remediation technologies as well as identify technically feasible remediation strategies for contaminated sites of different characteristics. 2 AFTER THIS LECTURE YOU SHOULD BE ABLE TO Recognise different strategies of remedial measures Divide techniques according to their way of taking care of the contaminants Recognise the most common techniques Take into account other important aspects than contaminant type when choosing remedial measure 3 CONTAMINATED SITES IN SWEDEN 80 000 potentially contaminated sites About 1300 estimated to pose substantial threats to human health and/or ecosystems About 100 of those have been remediated One of the largest expenditures at the Swedish Ministry of Environment Remediation a part of almost all construction and urban development projects 4 CONTAMINATED SITES IN WESTERN SWEDEN Approximately 10 000 potentially contaminated sites In cities like Gothenburg former industrial sites with a central location are interesting for exploitation purposes 5 STRATEGIES In-situ = treatment in the ground, always on-site. Ex-situ = implies excavation, contaminants are either treated on-site, off-site or not treated at all, if only slightly contaminated. 6 SOURCE- PATHWAY-RECEPTOR (SPR) CONCEPT Source barrier Pipings Receptor barrier Contaminant Surface water Receptor source Groundwater Pathway barriers Exposure at Source Transport pathway receptor 7 THE MOST COMMON METHOD Contaminated material is removed, commonly by excavation, and transported to permitted off-site treatment and disposal facilities. Pre-treatment may be required. 8 SOIL AND GROUNDWATER REMEDIATION Concentration techniques = concentrate contaminants before disposal, containment or destruction. Destruction techniques = destroys contaminants and alter them into less harmful products. Immobilization techniques = restrict contaminant movement and/or bioavailability. 9 Soil, sediment, bedrock and sludge Concentration Destruction Immobilization In-situ Soil flushing Biological degradation Stabilisation/ solidification (I) Vacuum extraction (Soil Thermal treatment Vapor Extraction, SVE) Vitrification Bioventing Thermal methods Landfilling Enhanced Bioremediation Electro kinetic methods Cover (cap) system Chemical reduction/oxidation Fracturing Phytoremediation Ex-situ Separation (Sieving) Incineration Stabilisation/ solidification (E) Soil washing Slurry phase bio treatment Thermal desorption Landfarming Chemical extraction Dehalogenation Biological degradation Pyrolysis Hot Gas Decontamination Composting Open burn/detonation Chemical reduction/oxidation Biopiles 10 10 Ground and Surface water including leachates Concentration Destruction Immobilization In-situ Air sparging Monitored natural attenuation Deep well injection (I) In-well Air stripping Chemical reduction/ oxidation Physical barriers Thermal Treatment Phytoremediation Passive/reactive treatment walls (Filter techniques and Enhanced bioremediation reactive barriers) Hydro fracturing enhancements Bioslurping Dual phase extraction Directional wells Ex- Separation Bioreactors situ Sprinkler irrigation Constructed wetlands (E) Ion exchange Advanced oxidation process Air stripping Pump and treat Adsorption/Absorption (Assuming pumping) Granulated Activated Carbon/Liquid Phase Carbon Adsorption Precipitation/Coagulation/Flocculation 11 11 SOIL VAPOUR EXTRACTION (SVE) I/C In-situ treatment of soil contaminated by volatile organic substances By applying a vacuum in the soil contaminants are set to migrate to the extraction system Efficiency enhancement by Electrical heating Injection of hot air or steam - ”Heat-Enhanced Vapor Extraction” or ”Steam Stripping” Can be applied under buildings and other constructions Relatively time-efficient under optimal conditions (0.5 - 3 years) 12 SVE WITH ”HEAT-ENHANCED VAPOUR EXTRACTION” OR ”STEAM STRIPPING” 13 LIMITATIONS OF SVE Only applicable to unsaturated zone – may need combination with methods for saturated zone Only efficient in permeable materials Heterogeneities can lead to decreased efficiency Additional treatment of extracted gases 14 DENSE NON-AQUAEOUS PHASE LIQUIDS (DNAPLS) Chlorinated aliphatic hydro-carbons Used as solvents and for extraction purposes Mechanical, chemical engineering, and electronics industries; dry cleaning 1000s of sites in Sweden Complex contaminant transport 15 DNAPL TRANSPORT TO DEEPER SOIL LAYERS AND INTO ROCK FRACTURES Long-lasting contaminant sources Vapor transport Contaminants degrade into other compounds, some less harmful, some more harmful E.g. vinyl chloride (VC), which is carcinogenic 16 IN-SITU THERMAL DESORPTION (ISTD) I/C ISTD uses thermal conductive heating (TCH) elements to directly transfer heat to soil/water/rock media. The process can be applied at low (100 °C) temperatures. For remediation of a wide variety of contaminants, both above and below the water table. Works in highly heterogeneous environments, e.g. fractured clay, fractured rock, low permeability soils. Vaporized contaminants are collected from vapor extraction wells and treated. Examples on contaminants: VOCs, semi-VOCs, PCB, pesticides, dioxines/furanes, volatile heavy metals (Hg, As) 17 ISTD REMEDIATION OF DNAPLS IN FRACTURED ROCK AND SOIL Sometimes combined with: Hydraulic control => Pump-and-treat Chemical methods Biological methods Barriers 18 VAPOR TREATED IN LOCAL FACILITY Vacuum pumps Treatment by e.g. oxidization methods 19 ISTD Advantages: High levels of contaminant removal, also from low permeability zones Disadvantages High technical skill required High cost, energy use, and carbon footprint Incomplete heating may result in untreated areas Large number of boreholes needed 20 EX-SITU THERMAL DESORPTION (ESTD) E/C Soil is heated (100-800 degrees C) to vaporize contaminants E.g. rotating ovens, electrically heated plates Mobile or permanent constructions Examples on contaminants: VOCs, semi-VOCs, PCB, pesticides, dioxines/furanes, volatile heavy metals (Hg, As) 21 COMMENTS THERMAL METHODS Not applicable to inorganics (except Hg, As) In-situ techniques requires high technical skills Relatively expensive: Up to a few thousand SEK/ton contaminated soil (not including excavation and transport) May have a substantial environmental footprint (high energy consumption) 22 SEPARATION E/C Ex-situ method for remediation of contaminated soil Separation techniques concentrate contaminated solids through physical and chemical means: Gravity separation Magnetic separation Sieving Washing 23 SOIL WASHING E/C Two main approaches To separate fine fractions To add extracting agents to get contaminants into solution Metals, VOC, semi-VOC, PCB, pesticides, dioxins/furans, organic cyanides, radioactive substances, PAH, etc In the order of one thousand SEK/ton for full scale operations 24 SOIL WASHING 25 GROUNDWATER PUMP AND TREAT REMEDIATION Ex-situ method where groundwater is abstracted and typically aerated – removed contaminated air is treated. Volatile organics are partitioned from extracted ground water by increasing the surface area of the contaminated water exposed to air – air stripping. Contaminant remaining in water treated by e.g. active carbon Efficiency enhancement by heating Significant challenges in complex hydrogeological settings – backdiffusion a common problem 26 26 BIOLOGICAL DEGRADATION I/D The idea… 27 BIOLOGICAL DEGRADATION In-situ Biological degradation – adding of microbes Monitored natural attenuation, can require long times (up to 50 years) Ex-situ Composting – bioreactor (excavation + treatment) In situ & Ex situ Phytoremediation: use of natural plants Examples of contaminants: gasoline, jet fuels, light PAHs + some chlorinated solvents, e.g. trichloroethylene, tetrahloroethylene and methylenechloride 28 MONITORED NATURAL ATTENUATION (MNA) 29 STABILIZING/SOLIDIFICATION I+E/I In-situ or ex-situ remediation of contaminated soil Trap or immobilize the contaminants within their ”host material” Contaminants enclosed in a stabilized mass Cement the most common type of agent (also chalk, silicates, bentonite, zeolites, asphalt, activated coal, biochar, polyesters, urea) 30 PERMEABLE REACTIVE BARRIERS (PRB) I/C In-situ method remediation of contaminated groundwater Groundwater flows through barrier and contaminants are sorbed onto barrier mtrl Examples on barrier materials; granulated iron, peat, fly ash, activated carbon 31 PERMEABLE REACTIVE BARRIER A passive in situ treatment zone of reactive material that degrades or immobilizes contaminants in contact with groundwater. Permanent, semi-permanent, or replaceable units across the flow path of a contaminant plume. The media degrade, sorbs, precipitate, or remove chlorinated solvents, metals, radio-nuclides, and other pollutants. Materials used ZeroValent iron (Metals, Organics) Activated carbon (Metals, Organics) Zeolites (Metals, Organics, Radionuclides) Modified clays (Organics) Alternative mtrls, e.g. peat (Metals, Organics) 32 BENEFITS OF ON-SITE TREATMENT WITH COMBINATIONS OF TECHNIQUES With shorter distances and decreased amounts of transports, to and from the site: greenhouse gas emissions are reduced risks for accidents and hence injuries are reduced costs for disposal are reduced This is a more sustainable way of thinking about remediation 33 SOME WEB-SITES FOR MORE INFO http://www.frtr.gov http://www.epa.gov https://www.epa.gov/remedytech/introduction-green- remediation https://www.sustainableremediation.org/ 34 MANAGEMENT OF CONTAMINATED SITES JENNY NORRMAN ACE146 CONTENT Contaminated sites in a Swedish context International examples Risk assessment of contaminated sites Risk management of contaminated sites LEARNING GOAL To get an overview and an understanding of the context and management of contaminated sites Reading material for Swedish context: Compendium Remediation of Contaminated Sites in Sweden (naturvardsverket.se) (also on Canvas) ACE146 - Management of contaminated sites 3 DRIVING FORCES: 16 SWEDISH ENVIRONMENTAL QUALITY OBJECTIVES 4. A Non-Toxic Environment “The occurrence of man-made or extracted substances in the environment must not represent a threat to human health or biological diversity. Concentrations of non- naturally occurring substances will be close to zero and their impacts on human health and on ecosystems will be negligible. Concentrations of naturally occurring substances will be close to background levels.” Specified that contaminated sites are to be remediated to such extent that they pose no threat to human health or the environment – not reached in 2020! ACE146 - Management of contaminated sites 4  UPDATE OF OBJECTIVE 4: At least 25% of sites with very large risk (Risk Class 1) to human health or the environment are remediated by year 2025. At least 15% of sites with large risk (Risk Class 2) to human health or the environment are remediated by year 2025. The use of other remediation techniques than excavation and disposal, without pre-treatment of masses, increased by year 2020. Also related to other EQO: 8. Flourishing Lakes and Streams, 9. Good-Quality Groundwater, 10. A balanced marine environment, flourishing coastal areas and archipelagos, 15. A good built environment, 16. A rich diversity of plant and animal life ACE146 - Management of contaminated sites 5  THE SWEDISH ENVIRONMENTAL CODE (MILJÖBALKEN) January 1st, 1999: purpose of promoting sustainable development and ensuring a healthy and sound environment for present and future generations a more modern, stringent, and broad legislation, replacing 15 previous environmental acts Section 10: contaminated sites the operator or property owner is liable for investigation and remediation “Polluter Pays Principle” Retrospect until 1969 ACE146 - Management of contaminated sites 6 EU SOIL STRATEGY (LAUNCHED 2022) ” ACHIEVING GOOD SOIL HEALTH BY 2050 “ The vision for soil: By 2050, all EU soil ecosystems are in healthy condition and are thus more resilient, which will require very decisive changes in this decade. By then, protection, sustainable use and restoration of soil has become the norm. As a key solution, healthy soils contribute to address our big challenges of achieving climate neutrality and becoming resilient to climate change, developing a clean and circular (bio)economy, reversing biodiversity loss, safeguarding human health, halting desertification and reversing land degradation. Medium term objectives by 2030 (e.g.): Significant progress has been made in the remediation of contaminated sites EUR-Lex - 52021DC0699 - EN - EUR-Lex (europa.eu) ACE146 - Management of contaminated sites 7  WHAT CAN INITIATE A REMEDIATION PROJECT (SE)? In Sweden, the drivers for remediation projects are described as three ”tracks”: Enforcement (control of responsible part) Government grants (no responsible part) Exploitation (land use change) ACE146 - Management of contaminated sites 8 SEPA, 2021 ACE146 - Management of contaminated sites 9  SWEDISH ACTORS Problem owners: companies, municipalities, public actors. Consultants: sampling, assess risk, evaluate options Contractors: executing remediations Controlling authority: Controls and approves: municipalities or County Adm. Swedish EPA Naturvårdsverket – public funding, guidelines. County Administrations: inventory, prioritises, applies for funding Swedish Geotechnical Institute (SGI): expert support, coordinate R&D, research funds, handbooks Sveriges Geological Survey (SGU): can act as problem owner Networks: the Clean Soil Network, (International: NORDROCS, COMMON FORUM, NICOLE, SuRF) ACE146 - Management of contaminated sites 10 SEPA, 2021 ACE146 - Management of contaminated sites 11  NATIONAL PROGRAMME FOR SITES WITH NO RESPONSIBLE PART Inventory and risk classification Prioritisation of risk class 1 (1300 sites) and risk class 2 (14000 sites) sites at C. Adm. – applies for funding from SEPA For sites with high risk For sites where the land can be used for housing Investigations & remediation at selected sites ACE146 - Management of contaminated sites 12  INVENTORY & RISK CLASSIFICATION (MIFO) Based on existing information Historic inventory Few or no samples Ranking of risks Prioritization of further studies CONSEQUENCES (sensitivity, toxicity, amount) ACE146 - Management of contaminated sites 13 PROGRESS FOLLOW-UP Inventoried sites in risk class 1; main investigations completed and ongoing (publicly funded); main investigations completed and ongoing (control); measures completed and ongoing (publicly funded); measures completed and ongoing (control). ACE146 - Management of contaminated sites 14 SITES ON-GOING IN 2016 Publicly funded ACE146 - Management of contaminated sites 15 DO YOU KNOW OF ANY SITES THAT HAS BEEN REMEDIATED? ACE146 - Management of contaminated sites 16 EX. OF LARGE REMEDIATION PROJECTS AROUND GÖTEBORG Norra älvstranden Eriksberg Sannegården Lindholmen Kvarnbyterrassen in Mölndal (SOAB) Kvillebäcken Ale municipality: http://www.ale.se/download/18.49d0f2c8134d3 Surte glasbruk af5c1e8000111624/1363266788376/Broschyr+ Sanering+av+gamla+synder+2011.pdf Bohus Varv ACE146 - Management of contaminated sites 17  EXAMPLE CANADA Federal Contaminated Sites Action Plan (FCSAP) launched in 2005, 15-year, $4.2 billion (CAD) reducing environmental and human-health risks of federal contaminated sites ACE146 - Management of contaminated sites 18 EXAMPLE USA CERCLA (Comprehensive Emergency Response, Compensation and Liability Actinitiated by congress in 1980 “Superfund” goals: Protect human health and the environment by cleaning up polluted sites; Make responsible parties pay for cleanup work; Involve communities in the Superfund process; and Return Superfund sites to productive use. ACE146 - Management of contaminated sites 19 EXAMPLES FROM OTHER COUNTRIES? ACE146 - Management of contaminated sites 20 MANAGING CONTAMINATED SITES -A MULTIDIMENSIONAL PROBLEM Characterization Environmental risks Decision Economy basis Remediation technology Functionality Legislation ACE146 - Management of contaminated sites 21 CONTAMINATED SITE MANAGEMENT FRAMEWORK (SWARTJES, SECTIONS 1.1.4, 1.5 & 5) Sometimes Hazard identification Sometimes Dose Sometimes Effect assessment assessment ~”the amount of a Aims to determine the contaminant that possible adverse enters the human effects in the human body” body Comparing estimated exposure to critical exposure ACE146 - Management of contaminated sites 22 RISK ASSESSMENT ”Red book” (NRC, 1983) – original idea to create a scientific and objective tool in environmental protection field Hazard identification Exposure assessment Dose-response relationship, effect assessment, exposure-response assessment Risk characterization But – there are also subjective parts in a risk assessment what is the acceptable/tolerable risk? ACE146 - Management of contaminated sites 23  EXAMPLE ACCEPTABLE RISK LEVELS Acceptable human health risk for carcinogenic substances related to contaminated sites in Sweden: One cancer case in a population of 100 000 as a consequence of a life time exposure Similar levels in other countries, sometimes 10-6 Acceptable risk quotient (or hazard quotient) for non-carcinogenic substances: 1 mobile phase in the ground Unsaturated zone: water/air OR water/air/NAPLs Saturated zone: water/(D)NAPL Flow will occur in all present mobile phases The phases will influence eachother ACE146: NAPLs 13  MULTI-PHASE FLOW – BASIC CONCEPTS Saturation (S) Wettability Capillary forces Governs the movement of Interfacial tension the different Governs the (mobile) transport or Phase interference – Relative permeability phases spreading of competition about space a NAPL Partitioning – distribution of a contaminant in different phases ACE146: NAPLs 14  SATURATION, Si The saturation is a measure of the proportion of the pore space (voids) that is occupied by phase i 𝑉𝑉𝑖𝑖 𝑆𝑆𝑖𝑖 = Figure from: https://core.ac.uk/download/pdf/53848.pdf 𝑉𝑉𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣 Vi = volume of phase i (e.g. the volume of air, water OR DNAPL in the figure) Vvoids = total pore space volume (i.e. the total volume of air, water and DNAPL) ACE146: NAPLs 15  Reference fluid WETTABILITY (VÄTBARHET) Test fluid Wettability – the overall tendency of one fluid to spread on or to adhere to a surface in the presence of another liquid with which it is immiscible… Depends on the 2 liquids and the surface material The angle φ is a measure of the wettability φ < 90°: the test fluid is the wetting fluid over the reference fluid Figure credit to Fritjof Fagerlund, Uppsala Univ. ACE146: NAPLs 16 WETTABILITY (VÄTBARHET) Rule of thumb… Water and organic NAPLs are more wetting than air The wetting fluid: the fluid that tends Water is in general more wetting than organic NAPLs to occupy the smaller pore volumes Organic NAPLs are more wetting than water in organic and be found on solid surfaces material The non-wetting liquid is restricted to the larger pore spaces Mineral particle Think for yourself: in the system on the figure containing a b c air, water and NAPL, what is a and what is c? ACE146: NAPLs 17  CAPILLARY FORCE, PC = PNW - PW The difference in pressure over the surface between two fluids in a porous medium: Pnw – pressure in the non-wetting fluid, Pw – pressure in the wetting fluid Dependent on: Interfacial tension (compare surface tension, ytspänning: liquid to air, see figure) – the surface energy at the interface between two immiscible liquids. The greater attraction forces in the wetting fluid causes the interface to stretch out like a membrane. Explain the surface tension phenomenon with examples. (byjus.com) ACE146: NAPLs 18  CAPILLARY FORCE, PC = PNW - PW The difference in pressure over the surface between two fluids in a porous medium: Pnw – pressure in the non-wetting fluid, Pw – pressure in the wetting fluid Dependent on: Capillary rise (kapillär stighöjd)– the result of forces of attraction between a (wetting) fluid and the solid material in a porous medium https://perso.univ-rennes1.fr/joris.heyman/PDF/cargese2018/Or- Capillarity_Cargese_2018_v2.pdf ACE146: NAPLs 19  THE CAPILLARY FORCE… …depends on the geometry of the void space, the nature of the soilds and the liquids, and the degree of saturation (S). 1 For a non-wetting fluid to enter a saturated porous media, the capillary pressure of the 2 largest pores must be exceeded: 3 displacement pressure (gravity) Drainage: the non-wetting fluid replaces the wetting fluid Imbibition: the wetting fluid replaces the nonwetting fluid https://www.researchgate.net/figure/General-relationships- between-capillary-pressure-and-saturation_fig5_284910188 ACE146: NAPLs 20 RESIDUAL SATURATION (NAPL) Residual saturation (Snwr) – the volume of NAPLs trapped in the pores relative the total volume of the pores (”blobs and ganglias”) Also: the saturation at which NAPLs becomes discontinous and is immobilized by capillary forces Residual saturation: 0.75%-1.25% for light oil in highly permaeable media Up to 20% for heavy oil Greatest in the saturated zone (DNAPLs) Acts as contamination source for long time! ACE146: NAPLs 21  RELATIVE PERMEABILITY, kr The permeability (k, m2) depends on the porous medium (soil) The hydraulic conductivity (K, m/s) is a measure of the ability of water to flow through a saturated porous medium and depends both on the medium and on the fluid If we know k, we can calculate K for any other fluid using the specific density (ρ) and viscosity (μ) of the fluid: K = (ρg/μ) × k When there are more than 1 fluids in the porous medium, there is competition about the pore space – the permeability is reduced for each phase i This is described using the relative permeability (kri), which varies between 0 and 1: ki = kri × k ACE146: NAPLs 22 Relative permeability, kr kr varies between 0 and 1 and depends on the saturation (Si) w – wetting phase nw – non-wetting phase ACE146: NAPLs 23 DARCY’S LAW FOR MULTIPHASE FLOW For a single phase in saturated porous media: q = -K × i = -ρgk/μ × δh/δx The total head (h) can be divided into an elevation head (z) and a pressure head (p/ρg) and rewritten accordingly: q = -k/μ × (δp/δx – ρg δz/δx) → q = -k/μ × (∇p – ρg ∇z) The minus signs are for the flow moving from a higher to a lower elevation, and that the direction of the gravitational constant g is opposite z For a given phase (fluid) i in a multi-phase flow system, this is written qi = -ki/μi × (∇pi – ρig ∇z) → qi = -krik/μi × (∇pi – ρig ∇z) ACE146: NAPLs 24 RELATIVE PERMEABILITY, EXAMPLE LNAPL Zone I: LNAPL saturation is high, water is restricted to small pores and the Kr of water is low. LNAPL mobile, continuous phase. Typical at large mobile product accumulations Zone II: both LNAPL and water as continous phases, the presence of one phase inhibits the permability of the other. Typical at the gw table Zone III: LNAPL is discontinous and trapped as residuals in isolated pores, flow is almost exclusively the movement of water. Typical below the gw table. ACE146: NAPLs 25 PARTITIONING – DISTRIBUTION BETWEEN DIFFERENT PHASES Gas Partitioning constants in a 4-phase system: phase Vapour pressure (ångtryck) (gas phase – free phase) Henry’s constant Free (gas phase – water phase) phase Water Solubility Soild phase phase (water phase – free phase) Solid – liquid partition coefficient (solid/adsorbed phase – water phase) ACE146: NAPLs 26  PARTITIONING – UNSATURATED ZONE Unsaturated zone/vadose zone: Soil particles, air, water, NAPL 4-phase system (adsorption, vapours, dissolved, immiscible (NAPL) phase) ACE146: NAPLs 27 PARTITIONING – SATURATED ZONE Saturated zone Soil particles, water, (D)NAPL 3-phase system (adsorption, dissolved, immiscible (DNAPL) phase) ACE146: NAPLs 28 BEHAVIOUR OF NAPLs IN SOIL AND GROUNDWATER Contamination situation if the penetration depth of the NAPL release does not reach the groundwater table Field scale! ACE146: NAPLs 29 BEHAVIOUR OF NAPLs IN SOIL AND GROUNDWATER Migration of NAPL is sensitive to changes in permeability Small pore throats means that very high displacement (or entry) pressure needs to be overcome by the non-wetting fluid Field scale! ACE146: NAPLs 30 BEHAVIOUR OF LNAPLs Increasing water saturation at the capillary fringe makes it more difficult LNAPLs accumulate at the groundwater for the LNAPL to penetrate to the table if sufficient volume is released groundwater table and lateral movement is possible ”Smearing” Field scale! ACE146: NAPLs 31 BEHAVIOUR OF DNAPLs HTTPS://WWW.YOUTUBE.COM/WATCH?V=CIT4M64W4JA DNAPLs continue to migrate through the DNAPLs continue to migrate downward until groundwater zone, if the penetration depth The volume of DNAPL is exhuasted, or reaches the groundwater table due to its It reaches a low permeable formation and migrates laterally density being higher than that of water Field scale! Field scale! ACE146: NAPLs 32 DNAPLs MIGRATION – COMPLEX! HTTPS://WWW.YOUTUBE.COM/WATCH?V=IOJK-RRIBL8 HTTPS://WWW.YOUTUBE.COM/WATCH?V=X7J2XPN2GEE Field scale! https://g360group.org/home/highlights/research-topics/bedrock-contaminant-hydrogeology/ ACE146: NAPLs 33 COMPLEXITY CONTINUES… Often mixes of chemicals, sometimes up to 30- 40 different compunds – very different properties than lab liquids… The chemicals get aged and the composition will alter over time Soil and rock heterogeneities, grain size distributions, stratigraphy, soil content of organic matter etc. ACE146: NAPLs 34 NAPLs – RISKS & REMEDIATION STRATEGIES Most likely exposure pathway for humans: inhalation of vapours Difficult to investigate – risk of spreading Important to locate the source – and preferably remove the source Technical protection (e.g. ventilation in buildings) Containment and cutting off transport pathways Mass reduction Digging, pumping (multi-phase), in-situ techniques to increase volatilisation or solubility Biological degradation in-situ Stimulated/augmented or natural ACE146: NAPLs 35 SOURCES AND FURTHER READING Most of the coloured and black-and-white figures are either directly from or redrawn based upon: https://www.epa.gov/sites/production/files/2015- 06/documents/lnapl.pdf https://www.epa.gov/sites/production/files/2015- 06/documents/dnapl_issue_paper.pdf Other sources are e.g. (there are plenty…): https://www.claire.co.uk/information-centre/cl-aire- publications (there are several sources on this site) https://www.nap.edu/read/9615/chapter/6 https://clu-in.org/PRODUCTS/AATDF/chap3.htm#E12E9 ACE146: NAPLs 36 ACE146 CONTAMINANTS IN SOIL AND GROUNDWATER, SEDIMENTS + TRANSPORT OF CONTAMINANTS LARS ROSÉN GEOLOGY AND GEOTECHNICS ARCHITECTURE AND CIVIL ENGINEERING CHALMERS UNIVERSITY OF TECHNOLOGY LEARNING OUTCOMES Develop conceptual site models for contaminated sites as a basis for sampling strategies and risk assessment. Apply methods to design site investigations and methods to evaluate sampled data at contaminated sites, as well as evaluate limitations and uncertainties. Apply methods for human health and ecological risk assessment at contaminated sites, and critically evaluate the result. 2 LITERATURE Chapter 10 in Fetter, C.W. 2014. Applied Hydrogeology. Fourth Edition. Pearson. 3 Contamination sources 4 CONTAMINANTS Per- and polyfluoroalkyl substances (PFAS) Fetter, 2014 5 CONTAMINATED SITES GÖTEBORG 6 6 TOPICS CONTAMINANT TRANSPORT An overview of major contaminant transport processes Introduce terminology Describe simple analytical solutions to assess contaminant transport Saturated groundwater flow conditions Excercises 7 CONCEPTUAL ILLUSTRATION 8 TRANSPORT PROCESSES Advection - the contaminant moves with the groundwater Diffusion and dispersion - the contaminant spreads as it moves Sorption - the contaminant movement is slowed down due to reaction with other solutes and the geologic media Decay - the contaminant degrades with time 9 ADVECTION 10 MECHANICAL DISPERSION Fetter, 2014 11 SORPTION AND DEGRADATION New Mexico Tech: www.ees.nmt.edu/.../research/SMZ/SM ZZVIProp.html 12 DECAY - DEGRADATION Example: factors affecting half-lives of microbial contaminants 13 GOVERNING EQUATION C  2C C Bd C *  C   DL 2  vx     t x dx  t  t  rxn dispersion advection sorption decay C = concentration of solute in liquid phase t = time DL = longitudinal hydrodynamic dispersion coefficient 𝑣 = average linear groundwater velocity Bd = bulk density of aquifer  = volumetric moisture content or porosity for saturated media C* = amount of solute sorbed per unit weight of solid rxn = biological or chemical reaction of the solute other than sorption 14 DARCY’S EXPERIMENT (1856) Flow: Q∝Δh Δℎ Q∝1/L 𝑄 𝐾𝐴 ∆𝑙 Δh Q∝A K = Hydraulic conductivity (m/s) h/l = Hydraulic gradient (m/m) A = cross-sectional flow area (m2) A Q Sand Q Specific discharge (flow): L 𝑞 𝐾 Q/A ∆ Flow in the direction of decreasing hydraulic head Also called Darcian velcity. 15 ADVECTION - PORE SCALE VELOCITY K(dh/dl) v̂ = ne where v̂ = average groundwater velocity (L/T) ne = effective porosity (%) Sometimes effective porosity is denoted kinematic porosity 16 BREAKTHROUGH CURVE Note! This is not a good representation of reality!! (more on this later!) 17 MASS FLUX OF CONTAMINANTS Specific flux (per unit area): F  vˆneC  qC Total flux: Ftot  FA  QC 18 PIEZOMETRIC MAP Stream 19 EXERCISE A contamination source (100 x 100 m) is located at point 1 on the piezometric map. Assume that the aquifer discharges to a stream at point 3 and that the contamination plume is 200 meters wide at this point. Chloride with an average concentration of 50 mg/l is being advected with the groundwater. What is the mass flux of chloride discharging to the stream? Variables: K = 10-4 m/s; ne = 0.2; b = 10 m; C = 50 g/m3 (b = saturated thickness of the aquifer at the outflow area to the stream) Where would you put your observation wells to best estimate the most relevant average concentration for your calculation? 20 SOLUTION Q = KiA = 10-4 m/s * 3/400 * 10*200 = 0.0015 m3/s Ftot = Q*C = 0.0015 m3/s * 50 g/m3 = 0.075 g/s = 2365 kg/year 21 21 DISPERSION - DIFFUSION No pure advective transport in the real world - spreading observed Due to combined effects of diffusion and dispersion 22  * DIFFUSION Because of concentration gradients (molecular scale process) Rate of diffusion described by diffusion coefficient 23 FICK’S FIRST LAW The mass of fluid diffusing is proportional to the concentration gradient: dC F   Dd ( ) dx F = mass flux of solute per unit area per unit time Dd = diffusion coefficient (L2/T) C = solute concentration (M/L3) dC/dx = concentration gradient (M/ L3/L) 24  2 2 Cations Dd (m /s) Anions Dd (m /s) DIFFUSION COEFFICIENTS H + 9.31E-09 OH - 5.27E-09 + - Na 1.33E-09 F 1.46E-09 + - K 1.96E-09 Cl 2.03E-09 + - Rb 2.06E-09 Br 2.01E-09 + - Cs 2.07E-09 HS 1.73E-09 2+ - Mg 7.05E-10 HCO3 1.18E-09 2+ 2- Ca 7.93E-10 SO4 1.07E-09 2+ 2- Sr 7.94E-10 CO3 9.55E-10 2+ Ba 8.48E-10 2+ Ra 8.89E-10 2+ Mn 6.88E-10 2+ Fe 7.19E-10 3+ Cr 5.94E-10 (Li & Gregory, 1974 in Fetter, 1999) 3+ Fe 6.07E-10 25 FICK’S SECOND LAW Concentrations change with time C / t  Dd  2C / x2 C/ t = change in concentration with time (M/L3/T) 26 EFFECTIVE DIFFUSION IN POROUS MEDIA D  Dd *  = tortuosity coefficient Tortuosity, T = transport path length / straight line distance = Le/L  =1/T and always < 1  = 0.01 - 0.5 for geological materials in laboratory tests (Freeze & Cherry, 1979) Diffusion process complicated because ions must maintain electrical neutrality 27 DIFFUSION RATE Solution to Fick’s second law:  x  C( x, t )  C0erfc 2 D * t  C(x,t) = concentration at distance x and time t since diffusion began C0 = original concentration (constant) erfc = complementary error function (based on assumption of a normal, or Gaussian, process) 28 ERROR FUNCTION x erf(x) erfc(x) x erf(x) erfc(x) x erf(x) erfc(x) 0 0.00000 1.00000 1.05 0.86244 0.13756 2.05 0.99626 0.00374 0.05 0.05637 0.94363 1.1 0.88021 0.11979 2.1 0.99702 0.00298 0.1 0.11246 0.88754 1.15 0.89612 0.10388 2.15 0.99764 0.00236 0.15 0.16800 0.83200 1.2 0.91031 0.08969 2.2 0.99814 0.00186 0.2 0.22270 0.77730 1.25 0.92290 0.07710 2.25 0.99854 0.00146 0.25 0.27633 0.72367 1.3 0.93401 0.06599 2.3 0.99886 0.00114 0.3 0.32863 0.67137 1.35 0.94376 0.05624 2.35 0.99911 0.00089 0.35 0.37938 0.62062 1.4 0.95229 0.04771 2.4 0.99931 0.00069 0.4 0.42839 0.57161 1.45 0.95970 0.04030 2.45 0.99947 0.00053 0.45 0.47548 0.52452 1.5 0.96611 0.03389 2.5 0.99959 0.00041 0.5 0.52050 0.47950 1.55 0.97162 0.02838 2.55 0.99969 0.00031 0.55 0.56332 0.43668 1.6 0.97635 0.02365 2.6 0.99976 0.00024 0.6 0.60386 0.39614 1.65 0.98038 0.01962 2.65 0.99982 0.00018 0.65 0.64203 0.35797 1.7 0.98379 0.01621 2.7 0.99987 0.00013 0.7 0.67780 0.32220 1.75 0.98667 0.01333 2.75 0.99990 0.00010 0.75 0.71116 0.28884 1.8 0.98909 0.01091 2.8 0.99992 0.00008 0.8 0.74210 0.25790 1.85 0.99111 0.00889 2.85 0.99994 0.00006 0.85 0.77067 0.22933 1.9 0.99279 0.00721 2.9 0.99996 0.00004 0.9 0.79691 0.20309 1.95 0.99418 0.00582 2.95 0.99997 0.00003 0.95 0.82089 0.17911 2 0.99532 0.00468 3 0.99998 0.00002 1 0.84270 0.15730 29 EXERCISE Consider a high concentration of chloride (brine) in solid waste deposited at a facility designed with a clay liner system at the bottom. The concentration in the leachate is assumed to be constant and much higher than in the pore water of the clay liner. Assume that both the waste and the clay liner are saturated and that there is no advective flow across the liner. Estimate the chloride concentration passing through the clay liner after 50 years. Variables: x (liner thickness) = 0,5 m; Dd = 2x10-9 m2/s;  = 0.5; C0 = 3000 mg/l 30  Diffusion - Solution to Fick's second law SOLUTION Diffusion 2 Dd (m /s) 2.00E-09  C ( x, t )  C0 erfc  x   2 D * t   0.5 D* 1.00E-09 C0 (mg/l) 3000 x (m) 0.5 t (år) 50 t(s) 1.58E+09 C(x,t) (mg/l) 2334.85 C(x,t)/C0 0.778283031 Leakage Groundwater concentration K (m/s) 1.00E-09 dh/dl 1 Year Concentration (mg/l) 2 Site area, B (m ) 10000 1 0.70 2 2.39 Cl concentration in groundwater 3 Q (m /s) 1.00E-05 3 3.76 4 4.79 14.00 Groundwater flow 5 5.60 12.00 Concnetration (mg/l) K (m/s) 1.00E-04 6 6.25 10.00 dh/dl 0.02 7 6.78 A (=b x W) (m ) 2 1000 8 7.22 8.00 9 7.60 6.00 3 Q (m /s) 2.00E-03 10 7.93 4.00 11 8.22 12 8.48 2.00 13 8.71 0.00 14 8.92 0 50 100 150 15 9.11 Years 16 9.28 17 9.44 31 31 MECHANICAL DISPERSION Faster transport in large pores Some particles take longer routes than others Friction differences within pores 32 DISPERSION The effects of dispersion are added to the diffusion coefficient to result in the hydrodynamic dispersion coefficient: DL   L vˆi  D * DT   T vˆi  D * DL = longitudinal dispersion coefficient [L2/T] DT = transverse dispersion coefficient [L2/T] v̂i = average linear velocity in direction i [L/T] L = longitudinal dispersivity [L] T = transverse dispersivity [L] D* = diffusion coefficient [L2/T] 33 APPARENT DISPERSIVITY The dispersivity is scale dependent The apparent longitudinal dispersivity can be estimated by the following relationship, based on statistical analysis (Xu & Eckstein, 1995): 2.414  L  0.83(log x ) x = distance 34 COMBINED EFFECTS OF DIFFUSION – DISPERSION For a slug injection: at any observation point downstream from the source, lower concentrations than the initial concentration at For a continuous injection: at any observation the source will be observed. Maximum well downstream from the source, the concentrations will decrease with distance, concentration will increase over time to reach but contamination will occupy increasingly the initial concentration at the source. larger volume. Hydrodynamic dispersion coefficient 35 1-DIMENSIONAL CONTINUOUS SOURCE Assuming only longitudinal hydrodynamic dispersion and continuous source: C0   L - vˆxt   vˆx L   L  vˆxt  C(L,t)= erfc    exp   erfc  2    DL   2 DLt    2 DL t  C(L,t) = the concentration at distance L at time t (M/L3) C0 = concentration at the source (M/L3) erfc = error function complement 36 PECLET NUMBER Describes the relation between diffusive and advective flow (dimensionless) vˆx Pe  DL v̂ = groundwater velocity x = distance from source to measurement point DL = hydrodynamic dispersion coefficient Advective dispersion is dominant for Peclet numbers > 10 37 APPROXIMATE SOLUTION TO CONTINUOUS 1D Valid for Peclet numbers larger than 10 C 0   x - vˆ x t  C(x,t) =  erfc   2   2 D L t  38 ERROR FUNCTION x erf(x) erfc(x) x erf(x) erfc(x) x erf(x) erfc(x) 0 0.00000 1.00000 1.05 0.86244 0.13756 2.05 0.99626 0.00374 0.05 0.05637 0.94363 1.1 0.88021 0.11979 2.1 0.99702 0.00298 0.1 0.11246 0.88754 1.15 0.89612 0.10388 2.15 0.99764 0.00236 0.15 0.16800 0.83200 1.2 0.91031 0.08969 2.2 0.99814 0.00186 0.2 0.22270 0.77730 1.25 0.92290 0.07710 2.25 0.99854 0.00146 0.25 0.27633 0.72367 1.3 0.93401 0.06599 2.3 0.99886 0.00114 0.3 0.32863 0.67137 1.35 0.94376 0.05624 2.35 0.99911 0.00089 0.35 0.37938 0.62062 1.4 0.95229 0.04771 2.4 0.99931 0.00069 0.4 0.42839 0.57161 1.45 0.95970 0.04030 2.45 0.99947 0.00053 0.45 0.47548 0.52452 1.5 0.96611 0.03389 2.5 0.99959 0.00041 0.5 0.52050 0.47950 1.55 0.97162 0.02838 2.55 0.99969 0.00031 0.55 0.56332 0.43668 1.6 0.97635 0.02365 2.6 0.99976 0.00024 0.6 0.60386 0.39614 1.65 0.98038 0.01962 2.65 0.99982 0.00018 0.65 0.64203 0.35797 1.7 0.98379 0.01621 2.7 0.99987 0.00013 0.7 0.67780 0.32220 1.75 0.98667 0.01333 2.75 0.99990 0.00010 0.75 0.71116 0.28884 1.8 0.98909 0.01091 2.8 0.99992 0.00008 0.8 0.74210 0.25790 1.85 0.99111 0.00889 2.85 0.99994 0.00006 0.85 0.77067 0.22933 1.9 0.99279 0.00721 2.9 0.99996 0.00004 0.9 0.79691 0.20309 1.95 0.99418 0.00582 2.95 0.99997 0.00003 0.95 0.82089 0.17911 2 0.99532 0.00468 3 0.99998 0.00002 1 0.84270 0.15730 39 EXERCISE Assume that the leakage from the waste site located at point 1 in the previous advection (mass flux) example will result in a plume that can be approximated using the solution for 1-D, continuous source. C0 = 50 mg/l D* = 2x10-9 m2/s Calculate: a) L and DL between points 1 and 3 b) Peclet number c) C at point 3 after 3 years 40 ANALYTICAL SOLUTION - EXCEL 41 41 CONTINUOUS INJECTION INTO A 2D FIELD Q = injection rate of contaminant at concentration C0 b = aquifer thickness C0 (Q / b)  vˆ x  C ( x, y , t )  exp x W (0, B)  W (t D , B) 4 DL DT  2 DL  2 2 vˆx x 2 vˆx y 2 B  2 2  4 DL 4 DL DT 2 vˆx t tD  DL 42 SLUG INJECTION INTO A 2D FIELD A = area over which the contaminant is introduced into the aquifer at concentration C0 at point (x0, y0) C0 A  (( x  x0 )  vˆxt ) 2 ( y  y0 ) 2  C ( x, y, t )  exp   4 t DL DT  4 D L t 4 DT t  Assumes that the contaminant volume is large enough to saturate the full aquifer thickness in a short period of time. 43 EXERCISE: ACCIDENTAL BENZENE SPILL y-dir Q Release point Obs. well GW flow Well x-dir Fine sand Water table Silt Contaminant Medium sand Calculate the concentration at the well (x=50m, y=0m) after 1 month. (Note! Not in the abstracted well water!) Variables: C0 = 1500 mg/l; K = 10-3 m/s; dh/dl = 0.005; ne = 0.2 DL = 2.5x10-4 m2/s; DT= 2.5x10-5 m2/s, A = 10 m2 Compare results with obs. well (x=30m y=10 m) 44 SPECIAL CASE: MAXIMUM CONCENTRATION C0 A Cmax  4 t DL DT Describes the concentration at the center of mass of the contaminant plume at time t Flow direction 45 SOLUTION – EXCEL (X=50; Y=0) 46 46 SOLUTION – EXCEL (X=30; Y=10) 47 47 REMARKS DIFFUSION-DISPERSION Diffusion dominant process in low permeability media Diffusion generally negligible in high velocity environments Geologic stratification and velocity conditions are key factors “Back-diffusion” is a major problem in groundwater remediation using pump-and- treat techniques! 48 RETARDATION Due to adsorption and absorption processes From a practical aspect, the important factor is the potential for removal of the solute from solution - partitioning A common approach to account for the slowing of contaminant migration is the Retardation factor, R = velocity of groundwater/velocity of plume Kd-concept, describes the sorption of contaminants to geologic media or organic content of the media: vˆ  sorbed concentrat ion R= = 1+ b K d  1 vˆc  mobile concentrat ion b = bulk density of porous media (M/L3) Kd = distribution coefficient (L3/M)  = moisture content or porosity for saturated media 49 KD - DISTRIBUTION COEFFICIENT C*  K d C C* = mass of solute sorbed by dry unit of weight of solid (M/M) C = concentration of solute in solution in equilibrium with the mass of solute sorbed onto the solid (M/L3) Kd = distribution coefficient (L3/M) - equal to the slope of the linear isotherm C C Non-linear Kd * isotherms: * 1 Freundlich Langmuir C C 50  * ESTIMATION OF KD FOR ORGANICS foc = organic content of the soil Koc = organic carbon - water partitioning content K d  f oc  K oc chemical concentration sorbed to organic carbon (mg/g) K oc  chemical concentration in water (mg/ml) Coctanol K ow  Cwater Many organic chemicals are hydrophobic 51 ESTIMATIONS OF KD WITH RESPECT TO ION EXCHANGE Assumes linear relationship between dissolved and sorbed chemical. concentrat ion on solids Kd  concentrat ion in water 52 SORPTION – USE OF BARRIERS 53 DECAY Organic and radioactive contaminants may be subject to decay with time. First-order decay: C (t) = C  e - t c 0 Cc(t) = contaminant concentration at time t (M/L3) C0 = contaminant concentration at t=0 (M/L3)  = decay constant 54 DECAY, CONT. If T is half life: C/ C 0 = 1/2 = e- T or  = ln(2)/T = 0.693/T 55 ”ALL INCLUSIVE” ANALYTICAL TRANSPORT MODELS Continuous source (Domenico, 1987)  C0   x    1  4  0.5    x  vˆt (1  4 x / vˆ) 0.5  C ( x, y, z, t )    exp  1   x   erfc    8   2 x    v     2( x vˆt ) 0.5    y  Y / 2   y  Y / 2   erf   0.5   erf  0.5     2( y x)   2( y x)     zZ   z  Z  erf  0.5   erf  0.5     2( z x )   2 ( z x )  Instantaneous source (Beatsle, 1969)  C0V0   ( x  vˆt ) 2 y2 z2  C ( x, y , z , t )   0.5  exp      t   8(t ) ( Dx D y Dz )  1.5  4 Dx t 4 D y t 4 Dz t  v̂ = velocity of the contaminant 56 ANALYTICAL AND NUMERICAL MODELS 57 EXERCISE A spill of gasoline resulting on a benzene plume has occurred at the waste site at point 1 in the 1st exercise. The plume can be assumed to be subject to sorption. In order to perform proper remedial actions, it is of interest to know the time of travel of the center of mass of the contaminant plume from the waste site to a compliance level at point 2. (Koc values are listed e.g. in Table 3, p. 453 in Fetter (2014) Variables: log Koc = 0.97 ml/g; b = 1.8 g/cm3; foc = 0.01 59 EXERCISE An instantaneous spill of diluted trichloroethylene has accidentally happened at point 1 in the 1st exercise example. The plume is considered to be subject to linear sorption and first-order decay. Your client wants to know the distribution of the contaminants over time at point 2 in order to take proper remedial action. Use a proper model and calculate the concentration-time profile at point 2. Variables: C0 = 4000 mg/l Dx = 2.5x10-5 m2/s; Dy,Dz = 2.5x10-6 m2/s; V0 = 5 m3; T = 400 days 60 OVERVIEW OF HUMAN HEALTH AND ECOLOGICAL RISK ASSESSMENT PAUL DRENNING ACE146 2023-11-07 CONTENT Overview HH risk assessment of CS Overview of ecological risks typically considered in Sweden  LEARNING GOALS To get a basic understanding of human health exposure pathways typically considered in HHRA two different ways of characterising HH risks how to derive soil guideline values which types of ecological effects are considered in Sweden and levels of protection Related to the course learning outcome: Apply methods for human health and ecological risk assessment at contaminated sites, and critically evaluate the result. ACE146 - Overview of human health and ecological risk assessment 3 WHAT IS RISK ASSESSMENT OF CONTAMINATED SITES? A formalised framework, used to identify whether or not contaminated sites presents an unacceptable risk to human health, controlled waters, property or ecological receptors It is a part of the decision basis regarding remediation of a site ACE146 - Overview of human health and ecological risk assessment 4 Risk assessment is part of the contaminated site management framework Risk-based land management Sometimes Hazard identification Sometimes Dose Sometimes Dose- assessment response assessment ~”the amount of a Aims to determine the contaminant that possible adverse effects enters the human in the human body body” Comparing estimated exposure to critical exposure ACE146 - Overview of human health and ecological risk assessment 5  Human health risk assessment for contaminated sites: A retrospective review - ScienceDirect ACE146 - Overview of human health and ecological risk assessment 6 SOURCE – PATHWAY – RECEPTOR MODEL Air From Book: Soil and Groundwater remediation technologies (2020) ACE146 - Overview of human health and ecological risk assessment 8 ACE146 - Overview of human health and ecological risk Human health risk assessment for contaminated sites: A assessment retrospective review - ScienceDirect  Exposure pathways humans ACE146 - Overview of human health and ecological risk assessment 10 EXPOSURE PATHWAYS FOR HUMANS (SEPA MODEL) Swedish EPA, 2021 ACE146 - Overview of human health and ecological risk assessment 11 RISK CHARACTERIZATION 1. Comparing estimated exposure to a critical exposure: ”Forward” assessment → 2. Comparing soil concentrations to soil guideline values (Soil Quality Standards) ”Backward” assessment ← ACE146 - Overview of human health and ecological risk assessment 12 RISK CHARACTERIZATION Calculation of exposure (HH) Risk level (carcinogenic) HQ, Health Quotient (noncarcinogenic) Calculation of guideline values (HH) One value for each exposure pathway One combined value for all exposure pathways ACE146 - Overview of human health and ecological risk assessment 13 PRINCIPLEFOR CALCULATION OF HUMAN HEALTH EXPOSURE Transport and exposure pathways What type of data is needed? Source Receptor -Transport parameters for each substance -Exposure parameters, e.g. body weight, Total soil exposure duration, intake of vegetables and Estimated concentration water… exposure -Toxicity parameters for each substance Could also be assessed by biomonitoring (5.3.2) Human health risk characterization (principle 1) : The estimated human exposure is compared to a critical exposure. ACE146 - Overview of human health and ecological risk assessment 14  HAZARD ASSESSMENT (SECTION 5.4) Genotoxic carcinogenic contaminants: No safe dose, increasing dose does not affect the severity of the effect, but increases the probability of the effect to occur Slope factor (excess cancer risk per unit of concentration) Dose or exposure In Sweden, a lifetime excess cancer risk of 1 in 100 000 (i.e. 10-5) is used as the maximum acceptable risk level – a policy decision Contaminants with threshold effects: A threshold level is established and expressed as Tolerable Daily Intake, TDI (= the toxicological reference value). Thus, TDI is the maximum acceptable human exposure Dose or exposure ACE146 - Overview of human health and ecological risk assessment 15 PRINCIPLEFOR CALCULATION OF SOIL GUIDELINE VALUES Transport and exposure pathways What type of data is needed? Source Receptor -Transport parameters for each substance -Exposure parameters, e.g. body weight, Acceptable soil exposure duration, intake of vegetables and concentration water… Acceptable = -Toxicity parameters for each substance human guideline value exposure Calculation of acceptable soil concentration Human health risk characterization (principle 2): A guideline value (generic or site-specific) is compared to the soil concentration ACE146 - Overview of human health and ecological risk assessment 16 GENERIC VS SITE-SPECIFIC GUIDELINE VALUES Generic: General models for different types of land use (exposure parameters). Material and transport Soil Quality Standards parameters are generic. Derived for each substance. Target values Action level Preliminary remediation goals Site-specific: Model parameters are based on the …. actual material and transport properties and the actual exposure scenario (land-use). Derived for each substance What land use are we talking about, the land use today or the future land use? ACE146 - Overview of human health and ecological risk assessment 17 RISK ASSESSMENT OF CONTAMINATED SITES TYPICALLY PERFORMED IN STAGES Little or no sampling: Risk classification (purpose is typically to prioritise sites) Early-stage investigation performed: Tier 1, Simple risk assessment (typically use generic SGVs) - Screening Several investigations performed: Tier 2, Detailed risk assessment (typically use site-specific SGVs or more advanced methods) – Target/Trigger ACE146 - Overview of human health and ecological risk assessment 18 TYPES OF RISKS CONSIDERED IN SWEDEN (AND MANY OTHER COUNTRIES) Human health: long-term carcinogenic effects long-term non-carcinogenic effects acute effects/short term effects Ecological systems: effects in soil ecosystem effects in surface water ecosystem protection of groundwater resources ACE146 - Overview of human health and ecological risk assessment 19  POINTS OF DEPARTURE (SEPA) Assessment of risks to human health or the environment from contaminated sites should be carried out from both a short-term and long-term perspective. Groundwater and surface water are natural resources which are almost always worthy of protection. The transport of contaminants from a contaminated site should neither result in an increase in the background levels, nor emissions which pose a long-term risk of reducing the quality of surface water and groundwater resources. Sediment and aquatic environments shall be protected so that no disruptions arise in the aquatic ecosystem, and so that especially protection-worthy and valuable species are protected. The soil environment shall be protected so that the ecosystem’s functions can be maintained to the extent needed for the intended land use. The goal shall be to have equal protection levels within an area which has the same overall land use, such as a residential area. The exposure from a contaminated site should not constitute the full exposure which a person can tolerate. Utgångspunkter för avhjälpande av förorenade områden Compendium Remediation of Contaminated Sites in Sweden ACE146 - Overview of human health and ecological risk assessment 20 ECOLOGICAL EFFECTS CONSIDERED IN SWEDEN (INTHEGUIDELINEVALUE MODEL) Effects in the soil ecosystem Effects in the surface water