Occurrence and Ecological Risks of Neonicotinoids in Wheat, Corn and Rice Field Soils in China

The global application of neonicotinoids (NEOs) has precipitated pervasive contamination of agricultural matrices, with China's staple crop lands representing critical exposure hotspots. The occurrence and ecological risks of ten NEOs in the field soils of three major crops (i.e., rice, wheat and corn) in China were investigated in the present study. Employing an optimized UPLC-MS/MS method (LOQ = 0.01-1.7 ng/g, RSD < 12.21%), ten NEOs across 69 representative field soils (rice: 23, corn: 18, wheat: 28) were quantified. It was found that the detection frequency (DF) of the NEOs was 100% in the soil. The DFs of NEOs in the soil followed the rule: imidacloprid (IMI, 100%) > thiamethoxam (TMX, 88.4%) > clothianidin (CLO, 87.0%) > acetamiprid (ACE, 46.4%) > dinotefuran (DIN, 7.2%) > nitenpyram (NIT, 1.4%). Mean total detected NEOs concentrations exhibited crop-dependent type: wheat (1.77-214.55 ng/g) > corn (0.79-97.53 ng/g) > rice (0.75-72.97 ng/g). The IMI, CLO and TMX triad constituted over 90% of the total contribution of detected NEOs. In addition, CLO and TMX in the rice soils, IMI, CLO and TMX in the corn soils and IMI, CLO and TMX in the wheat soils had medium ecological risks. Therefore, it is particularly important for agricultural ecological protection to strengthen monitoring and take effective measures to protect agricultural ecology.