Neonicotinoids in Qilu Lake Basin of China: Spatiotemporal Distribution and Ecological Risk Assessment

Neonicotinoids are extensively used to prevent and control crop diseases and insect pests. Qilu Lake Basin is an important agricultural area in Southwest China, with huge consumption of neonicotinoids. However, the lack of data on neonicotinoid residues in Qilu Lake Basin challenges us with assessing the environmental contamination levels and the potential risks for the local aquatic ecosystem. Therefore, in this study, the occurrence and spatiotemporal distribution of three neonicotinoids (imidacloprid, clothianidin, and thiamethoxam) in surface waters of Qilu Lake Basin were investigated. Their concentrations ranged from 0.65 ng/L (thiamethoxam in spring) to 1041.21 ng/L (imidacloprid in summer), which exhibited decreasing trends from the surrounding rivers to Qilu Lake. The highest concentrations were observed in summer, owing to the intensive application of pesticides and the heavy precipitation and surface runoff in this season. Imidacloprid and thiamethoxam presented relatively high ecological risks, and clothianidin was the most threatening compound, with high risk quotient values in every season owing to its low predicted no-effect concentration values and high toxicity.