Neonicotinoid Insecticides in the Qiantang River: Occurrence, Sources, and Ecological Risks for Sustainable Water Resources

Neonicotinoid insecticides (NNIs) can harm non-target species. This study examines NNIs’ distribution, sources, human exposure risks, and ecological risks in the Qiantang River’s water and sediment. NNIs concentrations ranged from 8.92 to 88.0 ng/L in water and 0.55 to 16.6 ng/g dw in sediment. The concentrations showed a trend of middle reaches > lower reaches > upper reaches. Agricultural activities were the main NNIs source, followed by wastewater treatment plants. Infants had the highest NNIs intake, with a daily intake of 15.4 ng/kg body weight, about 5.4-times higher than adolescents. Using the species sensitivity distribution and relative potency factor, the acute and chronic toxicity thresholds for aquatic organisms were estimated at HC5 values of 3636 ng/L and 40 ng/L, respectively. Species at lower trophic levels were more sensitive to NNIs. While acute risks to aquatic fauna are low, prolonged exposure poses potential risks to human and ecological health. These findings contribute to the enhancement of the regulatory framework for NNIs and serve as a reference for policymakers in formulating water pollution management strategies, thereby advancing the sustainable development of water resources in the region.