Fate of radiolabelled pesticides in aquatic microcosms

A microcosm system to assess the fate of pesticides in the aquatic environment is described. The 1 m3 microcosms are installed in a greenhouse and filled with a sediment layer of about 15 cm height and a water column of 750-800 l. An undisturbed sediment core (60 cm diameter, 60 cm depth) can be flanged at the bottom of the basin. Sediment and water are taken from natural ponds including benthic and planktonic biota. When the system has stabilized after an adaption phase of about 6-8 weeks, pesticides are applied as 14.C-labelled compounds by a technique simulating the natural entry path of pesticides into the aquatic ecosystem. The microcosms are maintained under partly standardized conditions and all fate relevant data of the applied pesticide, i.e. distribution, degradation, bioavailability and accumulation in water, sediment and biota can be determined