Leaching of Herbicides in Soil under the Influence of Different Rainfall Intensities

Herbicides play an important role in controlling weeds in agricultural crop areas. However, the lack of knowledge of their mobility in the soil may cause environmental damage, such as the contamination of soil and water bodies. Thus, this study was conducted to identify the effect of different rainfall intensities on the leaching potential of the herbicides diuron, hexazinone, and sulfometuron-methyl in red latosol. The trials were conducted in polyvinyl chloride columns. Rainfall simulations were performed for the following intensities: 10 mm h−1, 15 mm h−1, 20 mm h−1, and 25 mm h−1 of rainfall during 4 h. The columns were sectioned into seven layers (0–0.05; 0.05–0.10; 0.10–0.15; 0.15–0.20; 0.20–0.25; 0.25–0.30; 0.30–0.35 m), and the quantification of the herbicides in the layers was performed by Ultra-High Performance Liquid Chromatography coupled to the Mass Spectrometer. The diuron showed lower leaching potential in the soil, detected almost entirely in the upper layer of the column (0.0–0.05 m) for all precipitation applied. Hexazinone showed high leaching, being detected until the last layer of the soil (0.30–0.35 m) and in the water leached in the column when applied 20 and 25 mm h−1 of rainfall. Sulfometuron-methyl reached the last layer (0.30–0.35 m) when applied at an intensity of 25 mm h−1. Hexazinone showed higher leaching potential and consequent environmental risk. Diuron and sulfometuron-methyl were fewer mobiles in the soil profile; however, the environmental risk should be considered because higher rainfall intensities may alter their behavior in the soil.