Environmental mobility and potential contamination of water resources with pesticides in the Ribeirão Santa Maria sub-basin, Brazil

Pesticides are applied in agriculture to increase productivity. However, the continuous use of these compounds has caused the contamination of all environmental compartments. Pesticides can move through the air and soil, reaching surface or groundwaters. These dynamics are governed by their physicochemical properties, which predict the pesticide mobilities in the environment. In this work, we performed a prognosis of the mobility and environmental contamination of five pesticides (carbendazim, thiodicarb, diuron, fipronil, and chlorpyrifos) in the Ribeirão Santa Maria sub-basin in Brazil. The pesticides studied were the most used in the region, as defined after farmer interviews. The GOSS and the GUS indices were used to predict the pesticide mobilities in the environment. All the compounds analyzed were dangerous to the environment. Four of them were very dangerous. The studied pesticides have low solubility in water, lipophilicity, and strong affinity with soil components and aquatic biota, generating risks of bioconcentration and biomagnification. The GOSS and the GUS indices indicated that the five pesticides have a medium or low potential for contaminating groundwater. However, they have a medium to high potential for contaminating surface water. Thus, the pesticides applied to monocultures developed in the Ribeirão Santa Maria sub-basin show potential environment and aquatic fauna contaminations.