Metolachlor fate and mobility in a tidal wetland soil

A study was conducted to determine the fate of the herbicide metolachlor in a tidal wetland soil located along the James River in Virginia, USA. Soil adsorption/desorption and mineralization characteristics and mobility of metolachlor were determined on the Levy tidal wetland soil. The metolachlor Kd value was 65.8 L kg−1 and Koc value was 810 L kg−1 C−1, which are much greater than would be found on typical agricultural soils. After four 24-h desorption periods, the total amount of metolachlor that desorbed ranged from 16 to 22% of the amount initially adsorbed. Metolachlor mineralization was about 0.46% of the amount applied after 84 days, which indicates that it does not mineralize very readily in the Levy soil. The amount of metolachlor that leached from the soil columns averaged 1.64% of the amount applied after 84 days, showing a low degree of mobility. These results suggest that the Levy tidal wetland soil can function as an effective filter of metolachlor and other similar herbicides that enter via agricultural runoff, protecting surface and ground waters.