Ecotoxicity of zinc in spiked artificial soils versus contaminated field soils

Metal bioavailability is influenced by soil characteristics and aging perio d. In the present study, both factors were modeled by comparing metal bioav ailability in spiked artificial soil and historically contaminated field so ils. The chronic toxicity of zinc to Folsomia candida in spiked artificial soils could be predicted with a model based on pH, cation exchange capacity , and total zinc concentration. However, this model could not adequately pr edict chronic zinc toxicity in contaminated field soils. Porewater concentr ation and water- and calcium chloride-extracted zinc fractions of the conta minated field soils were lower than those predicted using models developed for spiked artificial soils, indicating that the effect of aging on metal b ioavailability should be taken into account. The reproduction of F. candida in contaminated field soils was lower than predicted with models developed using zinc concentration in the porewater and the water- and calcium chlor ide-extracted fractions in spiked artificial soils. This suggests that thes e fractions are not the only bioavailable zinc fractions and that dietary m etal exposure might also bean important route of uptake under environmental ly relevant conditions. Aging and dietary uptake should be studied urgently in order to be able to perform effect-based risk assessments of metal cont aminated soils.