APPENDIX 19A-10. Biological Uptake Factors

Transcription

1 APPENDIX 19A-10 Biological Uptake Factors

2 Table of Contents 1.0 EXPOSURE ASSESSMENT Biological Uptake Factors Soil to Terrestrial Invertebrates UP SI Organics Inorganics REFERENCES... 8 List of Tables TABLE 1-1: SUMMARY OF THE EQUATIONS, POINT ESTIMATES, AND RELEVANT CORRECTION FACTORS FOR SOIL TO TERRESTRIAL INVERTEBRATES... 6 Stantec 2010 PROJECT February

3 1.0 EXPOSURE ASSESSMENT To evaluate the level of exposure for each ecological receptor to each contaminant of potential concern (COPC) assessed in the ecological risk assessment (ERA), it is necessary to first estimate the concentration of each COPC in various media or biological tissues (e.g., soil and representative plant and animal tissues). A baseline sampling program was carried out to characterize the preexisting COPC concentrations in soil. The results of the background sampling program can be found in the main technical document. To estimate the potential environmental effects of the Project for each receptor location, modelled air concentrations and COPC deposition rates are used to estimate exposure point concentration (EPC) values for all COPC evaluated in this ERA. EPC values for soil, terrestrial plants, and small mammals (i.e., prey) were calculated using environmental fate and transport equations provided in US EPA (2005, Appendix A), where soil concentrations are additive to background concentrations. EPC values for soil invertebrates were calculated directly in the ERA model, using COPC-specific uptake factors which describe the relationships between chemical concentrations in environmental media and concentrations in biota. In the following sections, details of the equations and methods used to derive EPC values for biota in the ERA are discussed. The term uptake factor (UP) will be used generically in this document to refer to the specific term Bioaccumulation Factor (BAF), described as the ratio of a COPC concentration in an organism or biological tissue (e.g., a soil invertebrate) to the concentration in a surrounding medium (e.g., soil). Common sources of error in environmental fate and transport calculations involve confusion between wet and dry weight units for chemical concentrations in soil, sediment, and biota, and unit errors stemming from the fact that inorganic substances are commonly reported in units of milligrams (mg/kg) in environmental media, whereas many organic substances are reported in units of µg (micrograms), ng (nanograms), or even pg (picograms). To manage these problems in this ERA, all chemical concentrations are converted to units of mg/kg. For animal tissues, all concentrations are expressed on a wet weight basis (mg/kg wet weight tissue). The uptake factor literature is likewise inconsistent, with some uptake factors being expressed on a wet tissue basis and others on a dry tissue basis. The ERA model requires EPC values on a wet tissue basis for biota that are ingested as foods by ecological receptors. Therefore, where possible, uptake factors are expressed on a wet tissue basis; where necessary, correction factors are applied in order to convert from dry weight tissue units to a wet tissue basis. 1.1 BIOLOGICAL UPTAKE FACTORS The generalized uptake factor equation used to calculate a COPC concentration in an organism or biological tissue (e.g., soil invertebrates) from the concentration in a surrounding medium (e.g., soil) is as follows: EPC j = EPC i x UP ij Equation 1 Stantec 2010 PROJECT February

4 where: EPC j = exposure point concentration in biological compartment j (e.g., mg/kg wet weight soil invertebrate tissue); EPC i = exposure point concentration in environmental medium i (e.g., mg/kg dry soil); and UP ij = uptake factor from surrounding medium (in this case soil) to the target biological tissue (e.g., mg/kg wet tissue / mg/kg dry soil) Soil to Terrestrial Invertebrates UP SI Uptake factors for soil-to-terrestrial invertebrates (UP SI ) are generally reported for earthworms due to the availability of information in the literature, and a relative paucity of information with regards to insects. The ERA, therefore, focuses on earthworms as the "model" soil invertebrate, due to the relative abundance of data and models to predict contaminant uptake, as well as the perceived importance of earthworms in food webs. The UP SI are estimated in dry weight units (mg/kg dry soil invertebrate / mg/kg dry soil) and are converted to wet weight where necessary assuming that the fresh earthworm contains 84% water and 16% dry solids (typical value for earthworms; US EPA 1993). A summary of the equations, point estimates, and relevant correction factors for soil to terrestrial invertebrate uptake is provided in Table Organics The soil-to-earthworm bioaccumulation model for organic compounds, including PHCs and PAHs, is derived from US EPA (2005) as based upon Jager (1998), presented here to give the uptake factor on the dry weight basis for the earthworm (mg/kg dw tissue / mg/kg dw soil) and is calculated as: UP SI = ((f water + (f lipid x K ow )) / (F oc x K oc )) / 0.16 Equation 2 where f water is the water content of the worm (0.84; US EPA, 1993), f lipid is the lipid content of the worm (0.01), f OC is the fraction of organic carbon in soil (assumed to be 0.01), and K OC is the water to organic carbon partitioning coefficient (L/kg OC). The value 0.16 is the dry solids content of the worm. K OW and K OC values were obtained from various sources. K OW values used in the uptake equations were the same as those used in the fate and transport modeling. Bioavailability and metabolic factors (unitless) for use with this equation as multipliers before calculating the final concentration in earthworms were estimated based on K OW. Estimated values for bioavailability range from 0.1 to 1 while values for metabolic factor range from 0.05 to 1 (Table 1-1). Stantec 2010 PROJECT February

5 Inorganics Soil-to-earthworm bioaccumulation models for inorganic elements were derived (on a dry weight basis) from Sample et al. (1998; Table 12), for the following COPC: Copper UP SI =(e ( *ln(Csoil)) ) / C soil Equation 3 Lead UP SI =(e ( *ln(Csoil)) ) / C soil Equation 4 Manganese UP SI =(e ( *ln(Csoil)) ) / C soil Equation 5 Zinc UP SI =(e ( *ln(Csoil)) ) / C soil Equation 6 Point estimates of UP SI were also obtained from Sample et al. (1998) for aluminum, chromium (total and hexavalent), cobalt, molybdenum, nickel, strontium, and vanadium (Table 1-1). For these elements, the median values of data presented by Sample et al. (1998) were selected as follows: aluminum the median value (0.043) was selected, as the distribution was approximately lognormal; chromium the median value (0.306) was selected, as the distribution was approximately lognormal; cobalt - the median value (0.122) was selected, as the distribution was approximately lognormal; molybdenum - the median value (0.953) was selected, as the distribution was approximately normal; nickel the median value (1.06) was selected, as the distribution was approximately normal; strontium the median value (0.087) was selected, as the distribution was approximately normal; and vanadium the median value (0.042) was selected, as the distribution was approximately normal. Stantec 2010 PROJECT February

6 Table 1-1: Summary of the Equations, Point Estimates, and Relevant Correction Factors for Soil to Terrestrial Invertebrates COPC Petroleum Hydrocarbons UP SI Uptake Factor: (mg/kg-dry tissue / mg/kgdry soil) Uptake Factor Bioavailability Factor (Unitless) Aliph>C06-C08 - F1 1.54E+01 Jager (1998) 8.00E-01 Aliph>C12-C16 - F2 1.52E+01 Jager (1998) 4.00E-01 Arom>C12-C16 - F2 1.53E+01 Jager (1998) Aliph>C16-C21 - F3 1.52E+01 Jager (1998) 2.00E-01 Arom>C16-C21 - F3 1.53E+01 Jager (1998) 2.00E-01 Polycyclic Aromatic Hydrocarbons Anthracene 1.53E+01 Jager (1998) 2.00E-01 Fluoranthene 1.53E+01 Jager (1998) 2.00E-01 Fluorene 1.53E+01 Jager (1998) 2.00E-01 Phenanthrene 1.53E+01 Jager (1998) 2.00E-01 Benz(a)anthracene 1.52E+01 Jager (1998) Benzo(a)pyrene 1.52E+01 Jager (1998) Benzo(e)pyrene 1.52E+01 Jager (1998) Benzo(b)fluoranthene 1.52E+01 Jager (1998) Benzo(g,h,i)fluoranthene 1.52E+01 Jager (1998) Benzo(g,h,i)perylene 1.52E+01 Jager (1998) Benzo(k)fluoranthene 1.52E+01 Jager (1998) Chrysene 1.52E+01 Jager (1998) Dibenz(a,h)anthracene 1.52E+01 Jager (1998) Bioavailability Factor Small molecules with high solubility in both water and lipids. Bioavailability of aliphatic molecules decreases with increasing chain length. Bioavailability of aliphatic molecules decreases with increasing chain length. Bioavailability of aliphatic and aromatic molecules decreases with increasing chain length. Bioavailability of aliphatic and aromatic molecules decreases with increasing chain length. Metabolic Factor (Unitless) 5.00E E E-02 Metabolic Factor Readily metabolized. Readily metabolized. Readily metabolized. Less readily metabolized. Less readily metabolized. Stantec 2010 PROJECT February

7 Table 1-1: Summary of the Equations, Point Estimates, and Relevant Correction Factors for Soil to Terrestrial Invertebrates COPC UP SI Uptake Factor: (mg/kg-dry tissue / mg/kgdry soil) Uptake Factor Bioavailability Factor (Unitless) Indeno(1,2,3-cd)pyrene 1.52E+01 Jager (1998) Perylene 1.52E+01 Jager (1998) Pyrene 1.53E+01 Jager (1998) Chlorinated Monocyclic Aromatics Dichlorobenzenes 1.56E+01 to 1.58E+01 Jager (1998) Inorganics Aluminum Chromium (Total) Chromium VI Cobalt Copper Lead Manganese Molybdenum Nickel Strontium Vanadium Zinc 4.30E E E E-01 Concentration Dependant. Concentration Dependant. Concentration Dependant. 9.53E E E E-02 Concentration Dependant. Table 11 Table 11 Table 12 Table 12 Table 12 Table 11 Table 12 Bioavailability Factor Bioavailability assumed to be moderate when log Kow is between 3 and 5 Metabolic Factor (Unitless) Metabolic Factor Potential for metabolism assumed to be moderate when log Kow is between 3 and E+00 Conservative Default 1.00E+00 Stantec 2010 PROJECT February

8 2.0 REFERENCES Jager, T Mechanistic approach for estimating bioconcentration of organic chemicals in earthworms. Environ. Toxicol. Chem. 17: Sample, B.E., J.J. Beauchamp, R.A. Effroymson, G.W. Suter, and T.L. Ashwood Development and validation of bioaccumulation models for earthworms. Oak Ridge National US EPA Wildlife Exposure Factors Handbook. U.S. Environmental Protection Agency. Office of Health and Environmental Assessment, Office of Research and Development. Washington, D.C. EPA/600/R-93/187. US EPA Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities (HHRAP), Final. EPA530-R Stantec 2010 PROJECT February