Epsilon Archive for Student Projects

Abstract

Microcosm studies were performed to observe the effects of modern pesticides on denitrification and bacterial activity in lake sediment. Ecotoxicologically relevant test concentrations were retrieved from a Dutch study that presents Negligible Concentrations (NC) and Maximum Permissible Concentrations (MPC) for modern pesticides, i.e. concentrations critical for the environmental compartments water, soil, and sediment. Four functionally different pesticides, isoproturon (herbicide), deltamethrin and pirimicarb (insecticides) and captan (fungicide) were tested. None of the four tested pesticides had a consistent negative effect on bacterial activity or denitrification. Bacterial activity was, however, affected positively by pirimicarb. No other treatment effects were found for bacterial activity. Apparently, denitrification was affected positively by pirimicarb, isoproturon and deltametrin. Denitrifying bacteria seem to be able to use the tested pesticides as a carbon source when carbon deficiency prevails. A general decrease in denitrification over time for all treatments, especially in the controls, supports the theory that the denitrifying bacteria suffered from carbon depletion. Therefore, the addition of a carbon source in ecotoxicological studies with bacteria is recommended.