Occurrence of neonicotinoid insecticides in Hiuchi-Nada and Osaka Bay, Japan

Abstract

This study was performed to investigate the occurrence of selected insecticides (seven neonicotinoid insecticides and their four metabolites and the phenylpyrazole insecticide fipronil) in Hiuchi-Nada (48 samples) and Osaka Bay (4 samples), Seto Inland Sea, Japan, in 2016 and 2017. Among the insecticides examined, dinotefuran was exclusively detected in both the bays. Its concentration (9.45 and 32.4 ng/L in Hiuchi-Nada and Osaka Bay, respectively) and detection frequency (68.8% and 75.0% in Hiuchi-Nada and Osaka Bay, respectively) were the highest in September, which were closely related to its agricultural application. Furthermore, we observed a higher concentration of the insecticide in the surface layer of the water column than in the bottom layer. Considering that the water temperature was constant through the water column in September, insecticides were transported to estuarine areas and were eventually distributed around the surface waters of the bays. Finally, we inferred that the ecological risks posed by dinotefuran in the bay areas were expected to be too low to cause adverse effects on the resident estuarine and marine crustaceans examined.