Sorption kinetics of sulfometuron-methyl in different Brazilian soils.

The speed of the sorption reaction alters the bioavailability of herbicides in the soil and, consequently, the transport and transformation processes of the molecule in the environment. In this research, the sorption kinetics of sulfometuron-methyl was evaluated in different Brazilian soils in which sugarcane is grown. The sorption speed was carried out by the batch equilibrium method. The amount of sulfometuron-methyl adsorbed and remaining in the soil solution was used to build kinetic models in fifteen soils. Pearson's correlation coefficients were determined between maximum sorption capacity and soil properties. The pseudo-second-order model presented the best fit to report the sorption kinetics of sulfometuron-methyl in soils. The sorption equilibrium time varied between 69.1 and 524.7 min. The properties of cation exchange capacity (CEC), soil hydrogenionic potential (pH), and total organic carbon (TOC) affected the sorption kinetics of sulfometuron-methyl. The pH showed a negative correlation with the maximum adsorption capacity at equilibrium, while TOC and CEC positively correlated with the maximum adsorption. The results demonstrate that the sorption speed of sulfometuron-methyl varies between soils; this must be considered when defining the rate of use of the herbicide for weed control, minimizing the risk of environmental contamination.