Prediction of metal bioavailability in Dutch field soils for the oligochaete Enchytraeus crypticus

Current risk assessment procedures ignore that variation in soil properties results in substantial differences for uptake and effects in organisms in different soils. In this contribution is presented the results of a study o n the soil-related factors that modulate metal uptake and elimination by th e oligochaete worm Enchytraeus crypticus. Uptake of Cd, Cu, Ph, and Zn was quantified in 20 Dutch field soils as a function of time, Uptake rate const ants and equilibrium concentrations were estimated using compartment modeli ng, Internal metal concentrations varied less than the corresponding extern al levels. Zn and especially Cu provided the most extreme examples of this general behavior, which suggests regulation by the organism. Body residues by Cd increased linearly over time in 11 of the 20 soils studied, whereas i n the remaining 9 soils equilibration of internal Cd levels was observed, C aCl2 extraction could be used to discriminate the 9 soils in which there is Pb accumulation from the 11 soils in which bioavailable Pb levels were too low to allow for uptake. Multivariate expressions that describe uptake rat e constants and bioaccumulation factors as a function of soil characteristi cs were derived. pH and cation exchange capacity mere the most important pa rameters. The formulae were very similar to those describing partitioning o f metals over the solid and liquid phase of the soils, which suggests pore water-mediated uptake, A semimechanistic approach yielded further evidence of pore water-related uptake, modulated by competition between H+ and metal ions at the active sites of the membranes, (C) 1999 Academic Press.