Comparison of the fate of isoproturon in small- and large-scale water/sediment systems

A comparative study of the fate of the herbicide isoproturon using two different water/sediment systems, a small-scale laboratory system and a large-scale system (microcosm), was carried out in order to obtain information about possibilities for investigation and the applicability of the test results. Both of the test systems studied showed clear differences in the fate of the test substance as conditioned by the fundamental differences in size, complexity and incubation of the systems. The laboratory system prescribed by the BBA guideline IV, 5-1 showed significantly lower degradation of isoproturon than the microcosms. At the same time, however, it also produced relatively reproducible results that reflected the course of exposure and the metabolism of the test substance in essentially the same terms as the microcosms. Therefore, despite the limitations, small laboratory systems are useful instruments for examining the fate of pesticides in water and sediment. Microcosms are an impor tant supplement to existing small-scale systems.