Novel model describing trace metal concentrations in the earthworm, Eisenia andrei

We developed a novel model describing Eisenia andrei body concentrations fo r Cd, Cu, Pb, and Zn as a function of pH, metals, and soluble organic carbo n (SOC) in soil extracts for potential use in predicting values in contamin ated field sites. Data from 17 moderately contaminated Dutch field soils in which earthworms were cultured were used in model development. Model param eters quantify biological phenomena important for metal bioavailability, an d soil variables quantify relevant soil chemistry characteristics. Earthwor m body concentration (EBC) was modeled so that soil metal soluble at bulk s oil pH was considered available for dermal exposure, and gut exposure was d ue to soil metal in solution near neutral regulated gut pH. The efficiency parameter values indicated that metals are biologically regulated in the fo llowing order (most to least): Zn similar to Cu > Pb > Cd. The values deter mined for the exposure-route constant indicate that Cd, Cu, and Pb EBCs are almost exclusively (> 96%) due to dermal exposure and that only 18% of Zn EBC was due to gut exposure. The minimum healthful EBCs determined were Zn > Cu > Pb > Cd, and the values for Pb and Cd were near zero. The Cu model w as normalized by soluble organic carbon to be meaningful. The model was mos t accurate in describing Zn behavior.