Fate and effects of esfenvalerate in agricultural ponds.
The fate of esfenvalerate was investigated by sampling and chemical analysis after spraying of an artificial pond (25 g a.i./ha) and in the laboratory with [14C]esfenvalerate by trapping of 14CO2 and fractionation of the sediment. The effects were investigated on pelagic communities in enclosures in a natural lake and in the laboratory on surface (Cymatia coleoptrata) and sediment (Chironomus riparius) insects. The latter were used in sediment-plus-water and in water-only tests, measuring effects on emergence and mortality. The measurements in the artificial pond indicated exposure concentrations in the surface microlayer, water column, and sediment of 0.4 microgram/L, 0.05 microgram/L, and 9 micrograms/kg dry weight, respectively, two weeks after application. The degradation studies showed a limited mineralization (26.5%) of [chorophenyl-14C]esfenvalerate during 112 d. Part of the substance was transformed to water-soluble compounds (18.1%) or compounds attached to fulvic acids (26.2%), humic acids (14.2%), or nonextractable sediment constituents (8.8%). The formulated product Sumi-Alpha 5 FW caused 100% mortality to Cymatia coleoptrata after surface application of 0.13 g a.i/ha. Effects on zooplankton were recorded at 0.005 microgram/L of esfenvalerate. The 96-h median lethal concentration for first-instar larvae of Chironomus riparius was 0.13 microgram/L, whereas the delayed emergence lowest-observed-effect concentration was 0.8 microgram/L.