Comparison of Modeled Exposure Concentrations with Actual Concentrations for Ecological Receptors at a Large Superfund Site.* W. R. Alsop, M. E. Stelljes, E. T. Hawkins, and W. Collins, Harding Lawson Associates, 105 Digital Drive, Novato, CA 94949; and U.S. Department of the Army, Fort Ord, CA 93941
Ecological risk assessments often use measured soil concentrations to model concentrations of chemicals in various organisms to estimate potential exposures and assess potential risks. In this study, soil concentration data for inorganic and organic chemicals of potential concern collected during a remedial investigation at an environmentally diverse Superfund site in California were used to estimate uptake and tissue concentrations into both grasses and succulents. Different models were used for inorganic and organic chemicals. For inorganic, a single plant uptake factor was used to model concentrations into plants; for organics, a regression equation based on pesticides was used. These plant tissue concentrations were then used to estimate potential exposures for herbivores that were then used to estimate potential exposures for predators. Surface soil samples and collocated plants were collected and chemically analyzed to correlate soil concentrations and tissue concentrations. Small mammals were also sampled at the sites. These field data are compared with modeled plant and animal tissue concentrations, and the validity of such a modeling approach is discussed. Focus will be on the degree of conservatism of the modeling approach and differences in validity of the models for different groups of chemicals.
*Work supported by U.S. Army Corps of Engineers under Contract DACA05-86-C-0241.