Comprehensive Analysis of Pesticide Pollution across the Yangtze River Basin: Spatiotemporal Distribution, Socio-Economic Correlations, and Ecological Risk Assessment

As an important grain-producing region in China, the Yangtze River Basin is potentially threatened by pesticide contamination. In this study, occurrence, spatiotemporal distribution, possible drivers, and ecological risks of 40 pesticides including 23 herbicides, 8 insecticides, and 9 bactericides were investigated from Panzhihua to Nanjing of the Yangtze River. Atrazine historical data in the past two decades were used to analyze the impact of socio-economic development on pesticide residues. Results showed higher pesticide concentrations during wet and normal seasons than dry season, with mean concentrations ordered as normal season (182.18 ng/L) > wet season (157.20 ng/L) > dry season (69.65 ng/L). Several pesticides, such as atrazine, gestomine, isoprocarb, dichlorvos, diethyltoluamide, triadimenol, and isoprothiolane were the dominant pesticides with high detection frequency and concentration proportion. In addition, a decline trend of pesticides abundance was found from the Three Gorges to the subsequent section, indicating that the reservoir is likely to act as a sink for pesticide residues. Atrazine historical trends indicated pesticide pollution correlated with urbanization, per capita gross domestic product, and pesticide usage rather than wastewater discharge. Ecological risk assessment using the species sensitivity distribution (SSD) method exhibited that pesticides have no significant risks on aquatic organisms.