Pesticides in rainwater: A two-year occurrence study in an unexplored environmental compartment in regions with different land use in the State of São Paulo - Brazil.

Brazil's extensive agricultural area makes it the world's leading soybeans and sugarcane producer. Therefore, the use of large amounts of pesticides directly impacts all environmental compartments, including rainwater. We analyzed 14 pesticides and 5 degradation products in rainwater from three cities in the State of São Paulo, southeastern Brazil, with distinct land uses. We also correlated pesticide concentrations with climate parameters and remote sensing images and estimated the wet deposition fluxes in all cities. A risk assessment was conducted to evaluate potential risks to aquatic life, as rainwater may contributes to pesticide contamination of freshwater. Pesticide concentrations ranged from 0.1 to 596 ng L-1, including herbicides, fungicides, insecticides, and degradation products, with 100% detection frequency for atrazine and tebuconazole. The sum of wet deposition fluxes of pesticides in São Paulo (223 μg m-2) was about 3-fold lower than in the other cities with low population density and more agricultural activity (Brotas - 680 μg m-2 and Campinas - 701 μg m-2). Statistical analysis showed that the data from all cities differed from each other, with atrazine being the pesticide that contributed most to this difference, followed by carbendazim. Only two herbicides and one fungicide posed a risk to aquatic life. However, three insecticides and two insecticide degradation products had a risk quotient higher than 1, indicating that rainwater alone is a source of pesticide contamination. Thus, the use of rainwater for potable purposes must consider potential contamination, not only with pesticides.