High spatial resolved cropland coverage and cultivation category determine neonicotinoid distribution in agricultural soil at the provincial scale

Croplands are experiencing increasing neonicotinoid pollution and ecological health problems, which are especially widely applied in China. However, the large regional scale distribution of neonicotinoids and the key factors have seldom been determined. We show that the total residual concentration of neonicotinoids ranged from 13.4 to 157 ng/g with an average level of 75.8 ng/g and imidacloprid which was the dominant compound ranged from 10.4 to 81.3 ng/g during 2017-2021 in the Yangtze River Delta, China. In comparison, the neonicotinoid residues detected here were mostly higher than those in other regions. We further show that the 1-km spatial resolution cropland coverage (78.0%) and crop type (18.1%) predominantly contributed to the large spatial variation of neonicotinoids after adjusting for the factors including temperature, soil pH, soil moisture, and precipitation via automatic linear regression modeling at the provincial scale. Additional analyses revealed that tea croplands had significantly lowest concentration and fruit fields had the highest level due to the different application methods. Our findings provide new insight into key factors quantifying the high spatial resolved distribution of neonicotinoids and urgently call for reasonable application methods against rapidly growing ecology threats from neonicotinoid pollution in China.