太湖流域西北部地表水中农药的污染特征及生态风险评价

Distribution and Ecotoxicological Risk Assessment of Pesticides in Surface Water of the Northwest of Taihu Lake Basin

为研究太湖流域西北部地表水中农药的污染特征、时空分布及生态风险,分别于2019年3月(枯水期)和8月(丰水期)对目标区域的湖泊和重要河流中的农药进行监测分析。采用固相萃取结合高效液相色谱串联质谱法对120个地表水样品中的农药进行分析测定,共检测到7种杀虫剂和5种杀菌剂。整体上,枯水期农药污染较丰水期严重,农药总浓度的平均值分别为191.87 ng·L^-1和171.07 ng·L^-1。残留最高、分布最广的农药是吡虫啉(浓度范围ND^197.97 ng·L^-1,检出率98%)和多菌灵(浓度范围ND^114.44 ng·L^-1,检出率97%)。靠近农业区的漕桥河(S5和S6)和锡溧漕河(S36)是重污染区,漕桥河的S6点位是污染最严重的点位。采用风险商指数对农药进行生态风险评估,丰水期地表水中的农药对水生生物的威胁大于枯水期。有机磷类杀虫剂和苯并咪唑类杀菌剂对水生生物具有高风险,需要引起重视。

In order to investigate pollution characteristics,spatiotemporal distribution and ecological risk of pesticides in surface water in the northwest of Taihu Lake basin,pesticide residues in lakes and important rivers area were monitored in March(dry season)and August(rainy season)in 2019,respectively.One hundred and twenty collected surface water samples were analyzed by solid phase extraction(SPE)combined with liquid chromatography-tandem mass spectrometry(LC-MS/MS).Seven insecticides and five fungicides were determined in the samples.Concentrations of pesticides in surface water in the dry season were higher than in the rainy season,with average values of 191.87 ng·L^-1 and 171.07 ng·L^-1,respectively.Imidacloprid(concentration range ND^197.97 ng·L-1,detection rate 98%)and carbendazim(concentration range ND^114.44 ng·L^-1,detection rate 97%)were the two most contaminated and widespread pesticides.The seriously polluted areas were Caoqiao River(S5 and S6)and Xilicao River(S36)which are close to the agricultural area,and the most seriously polluted point was S6 of Caoqiao River.Ecotoxicological risk assessment of pesticides by calculating risk quotient(RQ)index in surface water during the rainy season was higher than that during the dry season.In addition,more attention should be paid to the organophosphorus pesticides and benzimidazole fungicides due their high risks to aquatic organisms.