Fresh additions of heavy metals do not model long-term effects on microbial biomass and activity

Previous work has reported adverse effects of long-term exposures of heavy metals (e.g. Cu, Ni, Cd and Zn) on soil microbial biomass (up to 50% decrease) and microbial activity at metal concentrations around current European Union permitted limits. Our aim was to see if we could model such changes in short-term (up to 50 days) laboratory incubations where soils were given a single pulse of metal salts. Such additions, however, caused only small changes in the measured variables. It was concluded that such short-term incubations are a poor model of changes in microbial biomass or activity due to chronic exposure to metals.