Experimental and modeling study of the fate and behavior of thiobencarb in clay and sandy clay loam soils

Abstract

Pesticides cannot be stopped today, but at the same time, it is impossible to accept the use of them without understanding their fate and behavior in the environment to accomplish their purpose and avoid their risks. To determine the behavior of thiobencarb in two common Egyptian soil types, clay soil and sandy clay loam soil, the adsorption–desorption isotherms, leaching, and dissipation processes were tested. Also, the obtained experimental data were modeled to predict the different processes and to determine the characteristic parameters of each process. Thiobencarb residues were measured by GC–MS and UV–Vis Spectrophotometer. The results indicated that thiobencarb dissipation is consistent with the 1st-order kinetic model, and the half-life is 10.61 days in clay soil and 10.24 days in sandy clay loam soil. The pseudo-second-order kinetic model and Freundlich isotherm model fit the experimental adsorption and desorption data. Both thiobencarb adsorption and mobility were significantly correlated. Compared with sandy clay loam soil, thiobencarb adsorption was greater in clay soil, producing S-type isotherms, whereas desorption in clay soil was lower, producing C-type isotherms. The leaching of thiobencarb is moderate in clay soil and sandy clay loam soil. However, it was significantly more leachable in sandy clay loam soil than in clay soil. Hence, it is very important to manage and pay attention to the irrigation of rice crop in order to prevent the leaching potential of herbicide thiobencarb and the threat to groundwater resources, as well as to avoid reducing weed control efficiency.