Degradation of pyrethroids in an aquatic ecosystem model

A study was conducted to evaluate the distribution of bioresmethrin, cypermethrin, deltamethin, permethrin, fenvalerate and Nurelle DX 550 EC (cypermethrin and chlorpyriphos) in an aquatic ecosystem model. The investigations were carried out at a temperature of 15–19°C in two different concentrations of each of the tested toxic substances in two parallel series. Cumulative effects and the influence of adaptation capabilities of microflora on their distribution were also studied. The degradation processes developed in accordance with the first kinetic order and depended on a group of determined compounds and initial concentrations. The pyrethroid half-live times at a temperature of 15–19°C fell within the range of 0.5–30.8 days. Chlorpyriphos, a component of Nurelle D 550EC, decomposed faster than most pyrethroids, its relevant half-live times were 5.0–7.1 days. In the case of sediments and organisms of the ecosystem, no accumulation effect of the pyrethroids was observed. However, a negative influence on the aquatic biocenosis was noted.