Regional Neonicotinoid Pollution in Wastewater Treatment\nPlants and Point Source Emissions

Neonicotinoids, currently the most\nwidely used insecticides, pose\necological risks to aquatic systems through runoff into waterways.\nWhile nonpoint source emissions have been studied, the spatial patterns\nof their point source emissions within watersheds remain poorly understood.\nHere, we quantified neonicotinoid residues in the influents, effluents,\nand various treatment stages of wastewater treatment plants (WWTPs)\nin the Yangtze River Delta, China. Results showed that influent concentrations\nwere significantly higher than those typically found in surface waters,\nwith municipal WWTPs exhibiting lower removal rates (53.1 ± 20.8%)\ncompared to industrial ones (83.3 ± 4.36%). WWTP influent neonicotinoid\nconcentrations were positively associated with precipitation and population.\nThe study identified the hydrolysis acidification process in industrial\nWWTPs and the aerobic sludge stage as key to higher neonicotinoid\ndegradation, with <i>Nitrospirota</i> and <i>Chloroflexi</i> as the dominant microbial degraders. Using these quantitative relationships\nand empirical degradation rates, we constructed a point source emission\nmodel. This model estimates the annual emission of neonicotinoids\nvia WWTPs at 5.27 tons/year (95% CI: 5.24–5.30 tons/year) in\nthe studied region, with municipal WWTPs accounting for approximately\n90%, especially during June and July. This study accurately assesses\nsecondary point source emissions, offering critical data for basin-wide\nneonicotinoid pollution control.