Soil-to-Small Mammal Concentration
Modeling ingestion exposures for carnivorous wildlife receptors requires information on chemical concentrations in vertebrate prey. Chemical concentrations in vertebrate prey are calculated from soil concentrations using point estimates of soil-to-vertebrate bioaccumulation factors (BAF) or soil-to-vertebrate tissue regression relationships. Regression relationships are the preferred means of calculating mammalian prey concentrations. When soil-to-tissue relationships are unavailable, it may be necessary to use diet-to-tissue bioaccumulation factors. In SADA, the simplifying assumption that carnivores eat small mammals has been made. This is because bioaccumulation factors for mammals are available for a wide range of chemicals whereas they are often lacking for birds and other vertebrates. Therefore, SADA refers to Fraction Mammal in the diet and Soil-to-Small Mammal BAFs.
Default Soil-to-Small Mammal point estimates appear as Custom BAFs. Defaults are largely based on data compiled by Sample et al. (1998) or EPA (2000). Users can modify these values if they have site-specific values or prefer values from a source other than that used to derive default values for SADA.
Kow-based soil-to-vertebrate or diet-to-vertebrate BAFs are not provided in SADA Version 3 based upon recommendations in EPA (2000).
Soil-to-vertebrate tissue regression relationships are of the form:
where Ctissue = Chemical concentration in vertebrate tissue (mg/kg, dry weight)
C soil = Chemical concentration in dry soil (mg/kg)
Slope = coefficient for slope of the regression model
Intercept = value for the y-intercept of the regression model.