Surfactant-mediated changes in leaching profiles of mesosulfuron-methyl, iodosulfuron-methyl and transformation products across different soil textures

Considering the environmental pollution risks associated with the use of herbicides, the impact of surfactant and physicochemical properties of soil on leaching potential of mesosulfuron, iodosulfuron methyl and their transformation products (TPs) was evaluated. Leaching of the studied herbicides was influenced by pH of the soil and herbicides leached more readily in alkaline soils than in acidic soil. Among alkaline soils, leaching was positively correlated with OM content of the soil. Addition of surfactant increased the leaching of herbicides and their TPs, resulting in lower residues in the upper layers and higher residues in the lower layers and leachates indicating greater potential for deeper soil contamination. Additionally, breakthrough curves for iodosulfuron methyl appeared earlier when the soil columns were treated with commercial formulation in the presence of surfactant. Among the different TPs, mesosulfuron (M1) and 2-[3-(4-hydroxy-6-methoxypyrimidin-2-yl) ureidosulfonyl]-4-methane sulfonamidomethyl benzoate (M2) TPs of mesosulfuron methyl and metsulfuron methyl (I1) and (methyl-2-(amino-sulfonyl) benzoate (I2) TPs of iodosulfuron methyl were detected. M2 has the highest mobility followed by M1 and I1 suggesting higher risk of M2 to contaminate lower soil profiles and groundwater thereby posing long-term ecological and human health risks. These findings emphasise the need for regulatory bodies to account for the combined effects of surfactants, soil properties and herbicide TPs while assessing the environmental impact of herbicide formulations.