Analysis of the concentration of pesticides in a watershed for public water supply in Brazil

The extensive use of pesticides leads to the contamination of water resources and consequent decrease in their quality. This study aims to assess the concentration of pesticides and the potential impacts on water quality in a reservoir for public supply. To assess the presence of pesticides in the reservoir, water samples were taken between the months of July 2017–March 2018, at the sections characterized by the catchment, inlet, and storage of the reservoir. For the identified pesticides, the Goss method was applied and analysis of the pesticides was performed using liquid chromatography coupled with high resolution mass spectrometry. Of a total of 54 pesticides analyzed, 30 were identified and detected at, at least, one point and over a sampled period, the most prevalent being carbendazim, which was identified in all sampled periods and sites. All the identified pesticides are characterized by a medium or high rating in the transport potential associated with sediment or dissolved in water. This work was the first of its kind in the study area and provides indicators of the negative impacts related to land use and pesticide use, on the quality of water for public supply. Considering that the identified compounds are not removed by conventional treatment methods, there is a need and urgency for government decision-making to regulate land use in the assessed watershed.