Risk of environmental contamination due to the hexazinone application in agricultural soils in northeastern Brazil

The behavior of herbicides as organic and inorganic colloids in soils depends on the pHysicochemical characteristics of the compounds, soil properties, and climatic conditions. Studies involving sorption, desorption, leaching, and dissipation of herbicides are essential to evaluate weed control efficiency and knowledge of the potential for environmental contamination. Thus, this study evaluated the behavior of hexazinone in Brazilian soils with different physical and chemical properties. Three agricultural soils with contrasting textures were used: Cambisol (sandy clay), Ferrasol (sandy loam), and Arenosol (loamy sand) from areas exempt from herbicide application. The quantification of hexazinone was performed using ultra-high-performance liquid chromatography coupled to a mass spectrometer (LC-MS/MS). The sorption (Kfs) and desorption (Kfd) constants of hexazinone showed differing soils with contrasting textures. The Ferrasol had the highest Kfs (0.46 mg kg(-1)), followed by the Arenosol (0.39 mg kg(-1)) and Cambisol (0.16 mg kg(-1)), whose desorption followed in the same order. The half-life (t(1/2)) of hexazinone in the studied soils showed similar values, with t(1/2) = 24 days for the Arenosol, t(1/2) = 23 days for the Cambisol, and t(1/2) = 22 days for the Ferrasol. The Cambisol showed greater leaching capacity, with a GUS index = 3.9, compared to the Arenosol and Ferrasol, which had a GUS index of 3.6 and 3.2, respectively. Soil pH and CEC were the main properties that influenced the sorption and desorption of hexazinone in the environment.