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RISK ASSESSMENT

RISK ASSESSMENT. Emissions. Transport and Fate. Concentrations. Exposure. Dose. Dose-response Relationship. Health Risk. Schematic overview of a Health Risk Assessment. THEME 2 TRANSPORT AND FATE. ENVIRONMENTAL EMISSIONS Air Stack emissions, incineration, manufacturing..

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RISK ASSESSMENT

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  1. RISK ASSESSMENT

  2. Emissions Transport and Fate Concentrations Exposure Dose Dose-response Relationship Health Risk Schematic overview of a Health Risk Assessment

  3. THEME 2 TRANSPORT AND FATE

  4. ENVIRONMENTAL EMISSIONS • Air • Stack emissions, incineration, manufacturing.. • Fugitive emissions (tanks of storage, leakage, waste storage) • Losses during use and transport • Water • Effluents treatment in production. • Spilling during production and distribution • Losses during transport • Storage after use • Soil • Controlled and uncontrolled spill. • Losses during use

  5. TRANSPORT OF CONTAMINANTS IN AIR • Gaussian plume shape (H – mixing layer height, h – stack height, H – plume height assuming flat terrain, H* - plume height above terrain)

  6. TRANSPORT IN AIR Air dispersion models: Gaussian plume model. where: c(x,y,z) = concentration of pollutant at receptor location (x,y,z) Q = pollutant emission rate (mass per unit time) u = mean wind speed at release height y =standard deviation of lateral concentration distribution at downwind distance z =standard deviation of vertical concentration distribution at downwind distance x h = plume height above terrain

  7. FATE MODELS

  8. DATA INFORMATION • Stack Information: • Location • Diameter of the stack • High • Flow Emissions • Gas Emission Temperaure • Gas speed • Concentrations of the contaminants

  9. Cartographic dates • Institut Cartogràfic de Catalunya (http://www.icc.es/downlod) • Buildings • Meteorological dates: • (Generalitat de Catalunya: http://www.gencat.es) • (Instituto Nacional de Meteorología: //www.inm.es) • (Ministerio de Medio Ambiente: //www.mma.es) • Wind speed and direction • Rainfall • Sum radiation • Air Estability

  10. Screenshot of MiraMon with the grid

  11. Elevation of the area (data from MiraMon/ Generalitat de Catalunya)

  12. Simulation of the particles distribution over the grid

  13. Pollution Transport Isopleth lines obtained from the Gaussian model (Industrial Source Complex, ISC 3) Particulate matter Gas phase Principal wind directions to: ENE (19.0 % ) NE (18.5 %).

  14. Air dispersion models • USEPA • (http://www.epa.gov/scram001/tt22.htm) • ISC3 • (http://www.air-dispersion-model.com/html/air-quality-des.html) • CALPUFF • (http://www.src.com/balpuff/calpuff3.htm)

  15. WATER DISPERSION MODEL GREAT-ER Geography-referenced Regional Exposure Assessment Tool for European Rivers. Waste water pathway of “down the drain” chemicals [Boeije (1999)]

  16. Overview over the GREAT-ER software structure

  17. Layer view of data groups

  18. GREAT-ER project modular approach [Boeije (1999)]

  19. A GREAT-ER screenshot, showing the Rur catchment. The river network and the cities in the densly populated area can be seen.

  20. FATE AND TRANSPORT IN SOIL MODFLOW

  21. DARCYS’S LAW dh Q = KA dL Q= Flow rate K = Hydraulic conductivity or coefficient of permeability (m/day) A= Sectional area dh/dL= Hydraulic gradient FLOW VELOCITY Q KA(dh/dL) dh v = = = K A A dL

  22. FATE AND TRANSPORT PRROCESSES • ADVENTION • DISPERSION • CHEMICAL PROCESSES • Precipitation/solution • Ionic Interchange • Redox processes • PHYSIS PROCESSES • Adsortion • Volatilization • BIOLOGICAL PROCESSES

  23. SUMMARY Key factors controlling environmental fate 1.- The prevailing environmental conditions 2.- Physical-chemicalsproperties 3.-The patterns of use

  24. THE NEED OF USING MULTICOMPARTMENT MODELS

  25. MULTI-COMPARTMENT ENVIRONMENTAL SYSTEM PARTITION MODELS These models describe the partition of the contaminant between various compartments

  26. CHEMODYNAMICS • Chemicals differ so greatly in their behavior. • Chloroform, evaporate rapidly and are dissipated in the atmosphere. • DDT, partition into the organic matter of soils and sediments and the lipids of fish, birds and mammals. • Phenols and carboxylic acids tend to remain in water where they may be subject to fairly rapid transformation processes such as hydrolysis, biodegradation and photolysis.

  27. PHYSICO-CHEMICAL PROPERTIES • The key properties are: • Solubility in water (Ks) • Vapor pressure (P) • Henry's Law Constant (H) • Octanol-water partition coefficient (Kow) • Air-water partition coefficient (Kaw) • Dissociation constant in water • Susceptibility to degrading • Transformation reactions. • Other essential molecular descriptors are: • Molecular mass (MW) • Molar volume (MV)

  28. Quantitative Structure-Property Relationships (QSPRs) The ultimate goal is to use information about chemical structure to deduce physical-chemical properties, environmental partitioning and reaction tendencies, and even uptake and effects on biota.

  29. Air-Water partitioning • Solubility in water and Vapor pressure are both "saturation" properties, i.e., they are measurements of the maximum capacity which a phase has for dissolved chemical. • Water Solubility • Is the concentration of a compound that is in equilibrium in a saturated solution at a given temperature. • Water Solubility ranges • Low solubility: < 10 ppm (mg/L) • Medium Solubility : 10 - 1000 ppm • High solubility > 1000 ppm

  30. Air-Water partitioning • Vapor pressure P (Pa) • Can be viewed as a "solubility in air” (mol/m3) • Is an indicator of the ability of a chemical to volatile. • Pa = P/RT ; R= 8.314 Pa m3 /mol·K • T = ºK • Low Vp: <1.0 E-06 mm Hg • Medium Vp: 1.0 E-06 - 1.0 E-02 mm Hg • High Vp > 1.0 E-02 mm Hg

  31. Air-Water partitioning • Henry’s law constant (H) : • Is a partition coefficient that expresses the ratio of the • chemical’s concentrations in air and water at equilibrium • and is used as an indicator of a chemical’s potential to • volatilize. • Henry's law constants can be calculated from the ratio of vapor pressure and aqueous solubility (H = Vp/ S ) • Vapor pressure and solubility thus provide estimates of air-water partition coefficients K or Henry's law constants H(Pa·m3 /mol), and thus the relative air-water partitioning tendency.

  32. Soil-Air partitioning • Koa. Octanol-air Partition coefficient • Characterize the partitioning of organic chemicals between the atmosphere and soil or foliage

  33. Organic-Water partitioning • Octanol-Water Partition Coefficient (Kow): • Equilibrium ratio of the concentrations of a chemical in n-octanol • and water, in dilute solution. • KOW = CO/CW • CO= concentration in octanol phase • CW = concentration in water phase • Provides a direct estimate of hydrophobicity or of partitioning O-W tendency from water to organic media such as lipids, waxes and natural organic matter such as humin or humic acid.

  34. Organic-Water partitioning • Kow ranges: • Low Kow <500 • Medium Kow : 500 - 1000 • High Kow > 1000

  35. Organic carbon partition coefficient (Koc) • Ratio of the amount of a chemical adsorbed per unit weight of • organic carbon in the soil or sediment to the concentration of the • chemical in solution at equilibrium. • mg adsorbed chemical / kg organic carbon • Koc = • mg of dissolved chemical /L of solution • Koc = foc * 0.48 Kow • Koc and the Kow indicates the chemical’s potential to bind to organic • carbon in soil and sediment. • The Koc and the Kow is used also to estimate the potential for an • organic chemical to move from water into lipid and has been • correlated with bioconcentration in aquatic organisms. Organic-Water partitioning

  36. Organic-Water partitioning • Koc values: • Koc <1000 will no be adsorbed to soil 0ºC • Koc =1000 –10 000 could behave either way • Koc >10 000 will adsorbed to soil

  37. Soil-Water partitioning • Adsorption Ratio (Kd): • Amount of a chemical adsorbed by a sediment or soil (i.e., the solid phase) divided by the amount of chemical in the solution phase which is in equilibrium with the solid phase, at a fixed solid/solution ratio. • It is generally expressed in micrograms of chemicalsorbed per gram of soil or sediment.

  38. Water-fish partitioning Bioconcentration Factors (BCF) The quotient of the concentration of a chemical in aquatic organisms at a specific time or during a discrete time period of exposure divided bythe concentration in the surrounding water at the same time or during the same period. BCF (Kb) = 0.05 K OW 0.05 corresponds to a 5% lipid content of the fish Kb , the organic carbon-water partition coefficient Sorption Coefficients:

  39. DEGRADATIONS FACTORS • HALF-LIVE • Time that it takes for the chemical to be reduced by one-half of its original amount • Depending factors: • Sunlight intensity (photolitic half-life) • Hydroxyl radical concentration • The nature of the microbial community • Temperature

  40. FUGACITY MODELS

  41. Thermodynamic Relationships • Fugacity “f” • Represents the partial pressure of chemical in a particular • medium and controls the movement of chemical between media. • Represent the “escaping tendency” and is identical to the partial pressure of ideal gases. • Fugacity (f) : (Pa) or (at)f= c/Z • c = concentration in the considered phase (mol/ m3) • Z= fugacity capacity (mol/m3 Pa) or mol/l at • Zw =1/H • By equilibrium between two phases f=0

  42. Applying the equation for ideal gases p V = R n T c = p/RT = f/(RT) Comparing with f= c/Z The fugacity capacity in airZa Za = 1/RT At equilibrium between water and air, the fugacity is the same in the two phases ca Za = cw Zw ca /cw = Zw /Za = Kaw Simirlaly between water and soil cs /cw = Zw /Zs = Ksw

  43. FUGACITY CAPACITY Zair = 1/RT (mol/m3 Pa) Z water = 1/H (mol/m3 Pa) Z soil = foc * Kow/H (mol/m3 Pa) Partition coeficients : ZAW = ZA/ZW (Air-water partition Coeficient) ZAS = ZA/Zs (Air-soil partition Coeficient) ZWsed = Zw/Zsed (water-sed partition Coeficient) ZwS = Zw/Zs (water-soil partition Coeficient)

  44. Example A chemical has a MW of 200 g/mol and a water solubility of 20 mg/l, which gives a vapor pressure of 1 Pa. The distribution coefficient octanol-water is 10,000 and Koc = 4000. How will an emission of 1000 moles be distributed in a region with an atmosphere of 6 x 10 8 m3, a hydrosphere of 6x106 m3, a lithosphere of 50,000 m3 with a specific gravity of 1.5 kg/l and an organic carbon content of 10%. Biota fish is estimated to be 10 m3 , specific gravity 1.00 kg/l and a lipid content of 5%. The temperature is 20ºC.

  45. Fugacities capacities: Za = 1/RT mol/m3 Pa Zw = 1/H = S/Pv moles /m3 Pa Zs = foc * Kow/H = foc Koc moles/m3 Pa Zbiota = foc * Kow moles/m3 Pa ZiVi = mol/Pa f= Total mol /ZiVi = Pa Concentrations: ca = fZa moles/m3 cw = f Zw moles/m3 cs = f Zs moles/m3 cbiota = f Zbiota moles/m3  = mols emission

  46. Solution Fugacities capacities: Za = 1/RT = 1/8.314 *293 = 0.00041 mol/m3 Pa Zw = (20/200)/1 = 0.1 moles /m3 Pa Zs = 0.1 x 0.1x 4000 = 40 moles/m3 Pa Zbiota = 0.1 x 0.05x10,000 = 50 moles/m3 Pa ZiVi = 0.00041x6x108 + 0.1 x 6x106 + 40 x 50000+ 10x 50 = = 2846500 mol/Pa f= M/ZiVi = 1000 moles /2846500 mol/Pa = 3.51 x 10-4 Pa Concentrations: ca = fZa = 3.51 x 10-4x 0.00041 = 1.44 x 10-7moles/m3 cw = f Zw = 3.51 x 10-4 x 0.1 = 3.51 x 10-5 moles/m3 cs = f Zs = 3.51 x 10-4 x 40 = 1.404 x 10-2 moles/m3 cbiota = f Zbiota = 3.51 x 10-4 x 50 = 1.755 x 10-2 moles/m3  = 999.2 moles ~ 100 mols emission

  47. FATE AND TRANSPORT How is a chemical moved in the environment by natural means? • AIR ENVIRONMENT • Photodegradate • Be inhaled • Be absorbed • Fallout in non-contaminate environment

  48. SOIL COMPARTMENT • Leach through the soil • Run off the soil • Adsorb in the soil • Biodegradate in soil • Accumulate in the soil • Bioaccumulate in plants and animals or be metabolized • Be phototransformer • Contaminate aquatic environment

  49. AQUATIC ENVIRONMENT • Biodegradate • Photodegradate • Bioaccumulate in aquatic organism • Volatilize • Contaminate plants, animals and well water • Adsorb to suspended and bottom sediment

  50. PLANTS COMPARTMENT • Be metabolized • Bioaccumulate • Be eaten by humans and other animals

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