Distribution characteristics and ecological risks of pesticide residues in agricultural soils in Houzhai River Basin, southwest Karst, China

<p indent="0mm"> This study investigated the distribution and ecological risks of pesticide residues in agricultural soils within karst earth critical zone of Southwest China, focusing on the Houzhai River Basin and its sub-basin, the Chenqi Basin. Forty-five typical pesticides were identified and quantified in soil samples using ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS). The results showed that the concentrations of pesticide residue in soils in the Chenqi Basin ranged from not detected (ND) to <sc>102.7 μg/kg,</sc> which were significantly higher than those in other areas of the Houzhai River Basin, especially in the topsoil. Rainfall significantly impacted the distribution of pesticide residues, leading to a general decrease in concentrations after rainfall. Ecological risk assessment indicated that carbendazim, chlorantraniliprole, and methamidophos posed a high environmental risk, imidacloprid, atrazine, and metribuzin posed a moderate risk, and the remaining pesticides posed low or negligible risks. These findings contribute to a better understanding of pesticide behavior in karst environments and provide a scientific basis for targeted management interventions to protect both human health and ecological environment safety.