Atrazine Transportation in a Sandy Soil in the Brazilian Cerrado

Savanna regions in Brazil are largely explored for agriculture production. This biome is also important for surface and groundwater availability, once it houses the springs of large river basins and parts of the Guarani Aquifer System outcrop zone. In the last 20 years, Brazil has experienced an exceptional increasing in agricultural production and this increase can be directly related to the use of mechanization, fertilizers and pesticides. The herbicides are the most sold among the agrochemicals. Atrazine is an herbicide used to grow sugarcane, sorghum, and corn plantation; and the states placed in Cerrado biome are the greatest consumers. Although this chemical was banned in many countries due to its toxic effects, in Brazil it is still in use. Despite of being a compound used since 1960, information of atrazine behavior in tropical soils is still missing. A wide variety of soil types in Brazil and the lack of information on tropical soils made the risk of contamination by atrazine even greater. In order to understand the behavior of this compound in Cerrado soils, experimental plots studies in a Cerrado region of São Carlos-SP have been carried out since 2017. The region presents an Entisol (82% sand). The current experiment has 6 experimental plots, 3 of them containing sugarcane and 3 without plant cover (bare soil). After rainfall events that generate runoff in the plots (rainfall events greater than 8 mm), samples of runoff, eroded soil, and leached solution are collected to perform atrazine balance in the unsaturated soil. The quantification of atrazine has been carried out using HPLC. The results indicated that the transport by runoff in the exposed soil plots reaches 10 times greater than in the sugarcane plots. Regarding the leaching process, they implied the high mobility of atrazine in sandy soil. Even in plots with sugarcane, where the organic matter content is higher, it was possible to identify the herbicide at 60 cm depth right in the first monitored rainfall. The experiment confirms the high mobility of the herbicide atrazine in a sandy soil, with potential for soil-water contamination. The results will also help to predict the potential for contamination of groundwater by atrazine.