Investigating the three-stage vertical movement of chlorantraniliprole and metolachlor, and their metabolites in soil and rice plants: A long-term lysimeter and soil column study

This study investigated the vertical movement of chlorantraniliprole and metolachlor, along with their metabolites, in soil and plant systems through a 500-day lysimeter and soil column experiment. The movement of pesticides was categorized into three stages: (1) downward movement in soil influenced by gravity, (2) uptake by plant roots, and (3) translocation within plant tissues. Chlorantraniliprole exhibited rapid downward mobility in soil, with its metabolite IN-EQW78 detected in soil layers but not in soil water, likely due to strong adsorption to soil particles. Transfer factors (TF) of chlorantraniliprole were highest in stems and husks, with values of 2.69 and 1.71 observed in the first year, and 5.33 and 2.37 in the second year, respectively, indicating efficient in-plant translocation.Metolachlor moved more rapidly toward groundwater, with its metabolites, oxanilic acid (OA) and ethanesulfonic acid (ESA), detected in lysimeter leachate at concentrations up to 5.2 and 3.5 µg/L, respectively, which were higher than those of the parent compound due to their high water solubility. These metabolites exhibited efficient translocation within plants but did not reach brown rice, possibly due to low residue levels and structural barriers. This study provides a three-stage predictive framework for assessing pesticide fate, offering insights to mitigate groundwater contamination and crop residue risks. Synopsis: A long-term study using undisturbed soil columns (lysimeters) that provides a comprehensive understanding of how pesticides move through soil, reach groundwater, and enter plants, offering essential data to support environmental safety management.