Neonicotinoids Persisting in the Sea Pose a Potential Chronic Risk to Marine Organisms: A Case from Xiangshan Bay, China (2015–2019)

Neonicotinoid insecticides (neonics) are extensively employed in agriculture and pervade various environmental matrices. However, few studies have documented the occurrence and potential chronic ecological risks of these chemicals in the marine environment. We collected 720 seawater samples from Xiangshan Bay during 2015–2019 and the integrated concentrations of seven neonics were determined using the relative potency factor method. Trend analyses using the Mann–Kendall test in time series, along with the estimation of the flux of neonics into the sea, were conducted. At last, the ecological risk of neonics was evaluated by water quality criteria derivation based on species sensitivity distribution. Our findings revealed that 47.6% of samples contained at least one neonic, with the integrated concentration of neonics ranging from 63.30 to 1684.14 ng/L. Imidacloprid and dinotefuran exhibited the highest frequency of detection in the analysis. The significance level of the Mann–Kendall test ranged from 2.16 × 10–10 to 1.21 × 10–5 (S > 0), indicating all neonics behaved with sharply increasing trends. Approximately 8.47 × 10–2 tons of neonics were discharged into Xiangshan Bay. Notably, the integrated concentrations of neonics represented a potential chronic ecological risk to marine organisms. This study provided novel insights into the spatial distribution, source, and migration of neonic species and their impacts on marine ecosystems.