Distribution and toxicity of current-use insecticides in sediment of a lake receiving waters from areas in transition to urbanization

Current-use insecticides including organophosphate (OPs) and synthetic pyrethroid (SPs) insecticides were analyzed in 35 sediment samples collected from Chaohu Lake in China, where a transition from a traditional agricultural to a modern urbanized society is ongoing. Total concentrations of five OPs and eight SPs ranged from 0.029 to 0.681 ng/g dry weight and 0.016–301 ng/g dry weight, respectively. Toxic unit analysis showed that 13% of the sediment samples likely produced over 50% of the mortality for benthic invertebrates. Analysis also showed that cypermethrin was the principal contributor to the toxicity. Spatial distribution evaluation implied that OPs were mainly from non-point sources associated with agricultural activities. Conversely, SPs may have been derived from runoff of inflowing rivers through urban regions, as their concentrations were well-correlated with concentrations of other urban-oriented contaminants.

► Though lower than urban sites, pyrethroid insecticides in Chaohu Lake, China may cause toxicity to benthic invertebrates.
► Concentrations of pyrethroids were well correlated with those of other urban-oriented contaminants, e.g. PAHs and LABs.
► Spatial distribution showed urban runoff was the major source of pyrethroids deposited in the lake sediment.
► Conversely, organophosphate insecticides were mainly associated with agricultural non-point sources.