Multi-Residue Occurrence and Environmental Risk Assessment in Surface Waters Under Intensive Agricultural Influence

Intensive agricultural activities have increased organic pollutant contamination of water bodies, posing significant risks to water quality, aquatic ecosystems, biodiversity, and human health. This study investigated the occurrence of 40 pesticides in surface waters of the Pirapó River Basin and assessed their potential risks to aquatic ecosystems and human health over two years. Water samples were collected seasonally at four sites between October 2021 and August 2023 and analyzed using solid-phase extraction coupled with LC-MS/MS and GC-MS multi-residue methods. Of the 40 compounds investigated, 25 (62.5%) were detected, whereas 15 (37.5%) were not found. Atrazine, carbaryl, chlorpyrifos, dichlorvos, glyphosate-AMPA, pendimethalin, permethrin, and toxaphene were detected in all samples. Concentrations of 2,4-D, carbaryl, chlorpyrifos, diuron, malathion, and toxaphene exceeded regulatory limits, indicating potential risks to aquatic biodiversity and human health. Human health risk assessment identified toxaphene as presenting a high non-carcinogenic risk (HQ > 1) at all sampling sites, while environmental risk assessment revealed high ecological risk (RQ > 1) for chlorpyrifos, diuron, and permethrin, and moderate risk for atrazine and glyphosate-AMPA. These findings demonstrate the persistent impact of pesticides on surface waters despite current regulations and highlight the importance of continuous biomonitoring to support environmental protection, safeguard public health, and guide sustainable water resource management.