Exploring the relationship between land-use and pesticides in freshwater ecosystem: A case study of the Araguaia River Basin, Brazil

Freshwater aquatic ecosystems are vulnerable to human activities within their surroundings, presenting a concerning scenario for aquatic organisms and human subsistence. Therefore, understanding the occurrence of pesticide contamination is a necessary condition to safeguard aquatic biodiversity and human health. We analysed the pesticide residues in water samples, using the solid-phase extraction (SPE) technique and determination by ultra performance liquid chromatography coupled with tandem mass spectrometry (UPLC‒MS/MS). We also we investigated whether land use influences water contamination by pesticides in the middle and upper Araguaia River basin, situated in the central region of Brazil in the Cerrado biome. We evaluated the effect of land use and land cover type on pesticide occurrence in nine subbasins using mixed linear models. We registered the occurrence of pesticides in all subbasins. After water analysis a total of eight pesticides were found: atrazine, carbendazim, cyanazine, imidacloprid, 2,4-D, clomazone, chlorpyrifos-ethyl, and imazalil. Atrazine and carbendazim were detected during both sampling years. The active ingredient atrazine and clomazone were registered in all studied subbasins, with concentrations ranged from 0.006-0.207 µg L−1. and 0.183-0.373 µg L−1, respectively. There were no significant relationships observed between the number of pesticides and the type of land use and land cover, a result possibly related to the short sampling period, as these pesticides are largely used for fungi and insect control in agricultural areas. The presence of pesticides in the water may have potentially detrimental effects on aquatic biodiversity because sampled pesticides have been associated with anomalies in ontogenetic development, diseases, and mortality in organisms. Based on European legislation, it was evident that most of the subbasins had pesticide concentrations in the water exceeding the safety levels for human consumption. Thus, it is crucial for Brazilian legislation to establish maximum limits for pesticide concentrations in water to ensure safe drinking water for the Brazilian population. Additionally, a permanent monitoring system should be established to understand contamination trends in this basin and to take appropriate actions to mitigate adverse impacts.