Residues of organophosphorus insecticides in sediment around a highly eutrophic lake, Eastern China

摘要

Purpose Organophosphorus pesticides (OPs) are significant stressors in the aquatic ecosystem of lakes due to their extensive use in agriculture. To understand the potential ecotoxico-logical risk of OPs, we examined the occurrence, distribution, and sources of 12 selected OPs in surface and core sediment samples collected around Chaohu Lake, one of the most eutrophic lakes in Eastern China. Materials and methods Eighteen surface sediments and four sediment cores were sampled from an important inflowing river and four main river estuaries around Chaohu Lake, respectively. All samples were analyzed for 12 selected OPs using a gas chromatograph equipped with a mass spectrometer. Results and discussion The results show that two thirds of the selected OPs were frequently detected around the lake, with detection frequencies of more than 60 %. Dichlorvos was the predominant OP, comprising 89.6 % of the total concentration of the 12 OPs (defined as ∑_(12)OP) in all samples. ∑_(12)OP in surface sediment and in core sediments ranged from 0.50 to 6.45 and 0.27 to 23.33 ng g~(-1) dry weight, respectively. High concentrations of ∑_(12)OP were found in estuaries of rivers flowing from agricultural lands, indicating that the selected OPs were mostly due to cultivation, and the vertical distribution of OPs in core sediments clearly showed the application history of OPs over the past few decades. The intercorrelation between OPs was likely affected by their sources, degradation rates, and deposition pathways. The poor correlation between OPs and total organic carbon (TOC) in the core sediments of Chaohu Lake might be ascribed to multiple sources of the TOC in Chaohu Lake. Conclusions Despite previous studies demonstrated that most OPs were not detectable in bottom sediments due to their high water solubilities and reduced persistence, in the present study, we found that most of the selected OPs were frequently detected in bottom sediment samples collected around Chaohu Lake, which have been identified with long-term eutrophication, suggesting that the OPs likely migrated from the water to the bottom sediment due to the occurrence of massive amounts of phytoplankton. Therefore, the environmental behavior and fate of OPs in a eutrophic lake require more attention given their ecotoxicity.