Resolution of the ongoing challenge of estimating nonpoint source neonicotinoid pollution in the Yangtze River Basin using a modified mass balance approach

Neonicotinoid insecticides have been widely consumed worldwide, particularly in China. There is a growing interest in the environmental research community about the occurrence, fates, sources, and risks of neonicotinoids. Nine neonicotinoids in river/lake water were measured at 12 sites along the Yangtze River Basin during the dry and wet seasons in 2016, and nonpoint sources were also identified based on a modified mass balance method. Significantly higher concentration of neonicotinoids was found during the dry season probably due to dilution effect and insecticide consumption. The high pollution levels are supposed to posing high ecological risks compared with the recommended thresholds. In 2016, 1,190 (95% confidence interval (CI): 822-1,690) tons of neonicotinoids were transferred into the adjacent sea. Nonpoint source pollution (1,700 (CI: 1,200-2,370) tons) was the major contributor (91.3%) to the total input of neonicotinoids into the system. Composition profiles identifying specific neonicotinoid...