Chemical behaviour of heavy metals and their bioavailability and toxicity to organisms: implications for environmental quality criteria

Abstract

Observed mortalities of Daphnia pulex exposed to a single concentration of zinc in different test waters are explained in terms of the chemical behaviour of zinc in solution, as predicted by chemical speciation modelling. Multivariate correlation analysis indicates that the hydrated zinc species, Zn2+, was primarily responsible for the observed Daphnia mortality. Although this method provides useful results in a well-defined laboratory setting, its application to field conditions proves to be less certain because of our incomplete understanding of processes affecting metal speciation in complex natural systems. These results indicate that metal bioavailability should be accounted for in the management of metal discharges into the natural environment.