Relating environmental availability to bioavailability: Soil-type-dependent metal accumulation in the oligochaete Eisenia andrei

Body residues are often better estimates of the amount of a chemical at the sites of toxic action in an organism than ambient soil concentrations, bec ause bioavailability differences among soils are explicitly taken into acco unt in considerations of body residues. Often, however, insufficient attent ion is paid to the rate and extent at which tissue concentrations respond t o soil concentrations and soil characteristics. In this contribution the im pact of soil characteristics on the environmental bioavailability of heavy metals for the oligochaete worm Eisenia andrei is reported. Uptake of As, C d, Cr, Cu, Ni, Pb, and Zn in 20 Dutch field sails and in OECD artificial so il was quantified as a function of time. Internal metal concentrations vari ed less than the corresponding external levels, Metal uptake and eliminatio n were both metal- and species-dependent. Worms typically attained steady-s tate concentrations rapidly for Cr, Cu, Ni, and Zn. Internal concentrations similar to those in the cultivation medium, linearly increasing body conce ntrations, or steady-state internal concentrations well above those in the cultivation medium were found for As, Cd, and Pb. Multivariate expressions were derived to describe uptake rate constants, steady-state concentrations , and bioaccumulation factors as a function of soil characteristics. Soil a cidity is the most important solid-phase characteristic modulating the avai lability of As, Cd, and Pb. Although additional semimechanistic calculation s yielded evidence of porewater-related uptake of Cd and Pb modulated by co mpetition between H+ and metal ions at the active sites of the membranes, t he findings for Cr, Cu, Ni, and Zn point to additional influences, among wh ich is probably regulation. (C) 1999 Academic Press.