Occurrence of neonicotinoids, sulfoxaflor, and two metabolites in precipitation in Japan

Abstract

Neonicotinoids and sulfoxaflor, widely used in Japanese rice cultivation, frequently contaminate aquatic environments due to their high-water solubility and persistence. Precipitation may facilitate their transport and deposition across environmental compartments. This study investigated the occurrence of these insecticides and two metabolites in precipitation, which may be overlooked because of their low volatility. About 28 precipitation samples collected over ten months from Ogata Village, an intensive rice cultivation area, were analyzed using the liquid chromatography-tandem mass spectrometry (LC-MS/MS). All samples contained at least one target compound (max total: 13.9 ng/L in August), with dinotefuran (7.24 ng/L) and sulfoxaflor (4.58 ng/L) peaking. Acetamiprid occurred in 100% of samples (including non-use periods), thiacloprid in 82% (with sporadic presence of its metabolite, thiacloprid-amide), and N-(6-chloro-3-pyridilmethyl)-N-ethyl-N′-methylformamidine (CPMF) (a metabolite of the rarely used nitenpyram) in 50% (mainly in winter). Despite low volatility, the presence of these insecticides and metabolites in precipitation may indicate a potential pathway for broader environmental dispersal.