Pesticide Pollution of Surface Waters: Investigating Agricultural Transformations and Community Exposure in Chile’s Central Valley

This study investigates the presence of pesticides in rivers in Chile’s Central Valley, taking a socioecological approach that seeks to create a dialogue between scientific analysis and community perceptions of those who live in rural territories. Exploratory sampling was carried out in three river basins in the Maule and Ñuble Regions (Putagán-Loncomilla, Ñiquén and Changaral rivers) during the southern summer of 2024. Samples were tested for 535 pesticides using gas and liquid chromatography techniques coupled with mass spectrometry. Diuron was quantified in the Putagán-Loncomilla and Ñiquén basins (≥LOQ = 0.01 mg/L), with concentrations in some cases exceeding international drinking water standards. Fosetyl-Al and its degradation byproduct, phosphonic acid, were also quantified in all samples analyzed. These findings confirm the persistence of certain agrochemicals in aquatic ecosystems and reveal the need for stricter regulations in Chile. This study also highlights the importance of integrating community knowledge in the identification of possible sources of pollution. Continuous monitoring of pesticides in the Central Valley’s rivers is recommended, in addition to a standard regulating their presence in surface waters and the adoption of mitigation strategies to reduce the impacts of pesticides on human health and the environment and further development of sustainable agriculture.