Legacy and Current-Use Insecticides in Agricultural Sediments from South China: Impact of Application Pattern on Occurrence and Risk

Legacy and current-use insecticides were, analyzed in sediments 'rcollected-from a typical rice-planting region in South China. Total concentrations of insecticides varied from to 775,ng g(-1) with mean and median values of 67.0 and 11.5 ng g-1, respectively. Pyrethroids' predominated peiStiade composition-(31.-.7%), followed by organophosphates (23.0%) and fiproles (20.8%). Sediment risk analysis showed that pyrethroids; fiproles, and abamectin posed significant risk to 'benthicinvertebrates in one-third of sediments. Different distrilyntiOnSof-pyrethroids and organophosphates in urban and agricultural areas were consistent with their application patterns,-vdiere-as legacy organoehiorine pesticides showed no region-specific distribution because of rapid transition of land use pattern-from iagriciiltural to urban areas. Likely illegal use of pyrethroids and fipronil caused serious ecological risks in agricultural waterways. Pyrietliroids and fipronil were.restricted to use in paddy fields, but their occurrence and risk in agricultural waterways were high, cafting for better measures to regulate the illegal use of insecticides.