1.1 MB pdf - Bolsa Chica Lowlands Restoration Project
1.1 MB pdf - Bolsa Chica Lowlands Restoration Project 1.1 MB pdf - Bolsa Chica Lowlands Restoration Project
SECTION 3: ANALYSIS Biotic Exposure Media Exposure point concentrations for the biota component of the diets for terrestrial and semiaquatic birds and terrestrial mammals were calculated based on tissue samples collected throughout each of the evaluation areas. Tissue concentrations for field-collected terrestrial plants, terrestrial invertebrates, bird eggs, small mammals, and fish were combined based on tissue type (e.g., terrestrial plants collected throughout each group of Cells, regardless of plant species, were grouped together). A 95th percent UCL was then calculated for the combined tissue group. The tissue concentrations for field-collected aquatic invertebrates were combined within evaluation area by species. The different species were not combined because different representative species would not feed on all the aquatic invertebrates collected. The exposure point concentration for each aquatic invertebrate species was either the 95 percent UCL or the maximum detected value, following the same rules as were applied to the other exposure media. The exposure point concentrations were previously presented in Tables 3-4 through 3-9. 3.1.4.3 Food Chain Uptake Model Contact with chemical stressors by higher trophic-level receptors (birds and mammals) must take into account intake of the various dietary items (biota tissue) that may have accumulated site contaminants, as well as intake of the abiotic media (sediment/soil and surface water). Food chain exposure estimates were calculated for representative terrestrial birds, semi-aquatic birds, and terrestrial mammals for the following exposures: • Belding's savannah sparrow - ingestion of terrestrial plants, terrestrial invertebrates, sediment/soil, and surface water • American kestrel - ingestion of terrestrial invertebrates, terrestrial vertebrates (small mammals and birds), sediment/soil, and surface water • Black-necked stilt - ingestion of aquatic invertebrates, sediment/soil, and surface water • Least tern - ingestion of fish, sediment/soil, and surface water • Black-crowned night-heron - ingestion of aquatic invertebrates, fish, small mammals, sediment/soil, and surface water • Western harvest mouse - ingestion of terrestrial plants, terrestrial invertebrates, invertebrates, sediment/soil, and surface water • Coyote - ingestion of terrestrial plants, bird eggs, small mammals, sediment/soil, and surface water To address this multiple pathway exposure, modeling was required. The necessary input parameters to the exposure model are outlined below. Exposure estimates for each representative species were generated based on model assumptions, life history parameters, and bioaccumulation factors (presented below), and exposure point concentrations (presented in Section 3.1.4.2). SAC/143368(003.DOC) 3-21 ERA REPORT 7/31/02
SECTION 3: ANALYSIS Model The general form of the food chain model used to estimate exposure of birds and mammals to COPECs in soil-sediment, surface water, and food items is as follows: Where: E t = E o + E d + E i E t = the total chemical exposure experienced by wildlife E o , E d , and E i = oral, dermal, and inhalation exposure, respectively Oral exposure occurs through the consumption of contaminated food, water, or soil-sediment. Dermal exposure occurs when contaminants are absorbed directly through the skin. Inhalation exposure occurs when volatile compounds or fine particulates are inhaled into the lungs. Although methods are available for assessing dermal exposure to humans (U.S. EPA 1992f), data necessary to estimate dermal exposure are generally not available for wildlife (U.S. EPA 1993c). Similarly, methods and data necessary to estimate wildlife inhalation exposure are poorly developed or generally not available (U.S. EPA 1993c). Therefore, for the purposes of this assessment, both dermal and inhalation exposure were assumed to be negligible. As a consequence, most exposure must be attributed to the oral exposure pathway. By replacing E o with a generalized exposure model modified from Suter et al. (2000), the previous equation was rewritten as follows: Where: N ⎡ ⎤ [ j s ] ⎢∑ ij i ⎥ + [ j × ] Eo = Soil × P × FIR + B × P × FIR Water WIR ⎣ i= 1 ⎦ E o = total oral exposure (mg/Kg/d) Soil j = concentration of chemical (j) in soil (mg/Kg) P s = soil ingestion rate as proportion of diet FIR = species-specific food ingestion rate (kg food/Kg body weight/d) B ij = concentration of chemical (j) in biota type (i) (mg/Kg) P i = proportion of biota type (i) in diet Water j = concentration of chemical (j) in water (mg/L) WIR = species-specific water ingestion rate (L/kg body weight/d) The end product or exposure estimate for external exposures for birds and mammals is a dosage (amount of chemical per kilogram receptor body weight per day [mg/Kg bw/d]) rather than a media concentration as is the case for the other receptor groups (fish and other aquatic organisms, terrestrial plants, and terrestrial invertebrates. This is a function of both the multiple pathway approach as well as the typical methods used in toxicity testing for birds and mammals. Sample calculations for exposure via food-chain uptake are presented in Appendix I, along with examples of risk estimation calculations. ERA REPORT 3-22 SAC/143368(003.DOC) 7/31/02
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SECTION 3: ANALYSIS<br />
Biotic Exposure Media<br />
Exposure point concentrations for the biota component of the diets for terrestrial and semiaquatic<br />
birds and terrestrial mammals were calculated based on tissue samples collected<br />
throughout each of the evaluation areas. Tissue concentrations for field-collected terrestrial<br />
plants, terrestrial invertebrates, bird eggs, small mammals, and fish were combined based<br />
on tissue type (e.g., terrestrial plants collected throughout each group of Cells, regardless of<br />
plant species, were grouped together). A 95th percent UCL was then calculated for the<br />
combined tissue group. The tissue concentrations for field-collected aquatic invertebrates<br />
were combined within evaluation area by species. The different species were not combined<br />
because different representative species would not feed on all the aquatic invertebrates<br />
collected. The exposure point concentration for each aquatic invertebrate species was either<br />
the 95 percent UCL or the maximum detected value, following the same rules as were<br />
applied to the other exposure media. The exposure point concentrations were previously<br />
presented in Tables 3-4 through 3-9.<br />
3.1.4.3 Food Chain Uptake Model<br />
Contact with chemical stressors by higher trophic-level receptors (birds and mammals)<br />
must take into account intake of the various dietary items (biota tissue) that may have<br />
accumulated site contaminants, as well as intake of the abiotic media (sediment/soil and<br />
surface water). Food chain exposure estimates were calculated for representative terrestrial<br />
birds, semi-aquatic birds, and terrestrial mammals for the following exposures:<br />
• Belding's savannah sparrow - ingestion of terrestrial plants, terrestrial invertebrates,<br />
sediment/soil, and surface water<br />
• American kestrel - ingestion of terrestrial invertebrates, terrestrial vertebrates (small<br />
mammals and birds), sediment/soil, and surface water<br />
• Black-necked stilt - ingestion of aquatic invertebrates, sediment/soil, and surface water<br />
• Least tern - ingestion of fish, sediment/soil, and surface water<br />
• Black-crowned night-heron - ingestion of aquatic invertebrates, fish, small mammals,<br />
sediment/soil, and surface water<br />
• Western harvest mouse - ingestion of terrestrial plants, terrestrial invertebrates,<br />
invertebrates, sediment/soil, and surface water<br />
• Coyote - ingestion of terrestrial plants, bird eggs, small mammals, sediment/soil, and<br />
surface water<br />
To address this multiple pathway exposure, modeling was required. The necessary input<br />
parameters to the exposure model are outlined below. Exposure estimates for each<br />
representative species were generated based on model assumptions, life history parameters,<br />
and bioaccumulation factors (presented below), and exposure point concentrations<br />
(presented in Section 3.1.4.2).<br />
SAC/143368(003.DOC) 3-21 ERA REPORT<br />
7/31/02
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