Pyrethroids constitute a group of widely used insecticides, which are toxic to aquatic organisms. This report presents the results from a 2-year study of the fate of pyrethroids in ponds, i.e. their distribution in the water column, the sediment and the surface microlayer respectively. The measurements are used to validate a distribution model and the model analysis is used for interpretation of the results. The model analysis demonstrates that pyrethroids are adsorbed in the upper few mm of the sediment
