Aminocyclopyrachlor sorption-desorption and leaching from three Brazilian soils.

This study aimed to evaluate the sorption-desorption and leaching of aminocyclopyrachlor from three Brazilian soils. The sorption-desorption of ¹⁴ C-aminocyclopyrachlor was evaluated using the batch method and leaching was assessed in glass columns. The Freundlich model showed an adequate fit for the sorption-desorption of aminocyclopyrachlor. The Freundlich sorption coefficient [K _{f (sorption)} ] ranged from 0.37 to 1.34 µmol ^(1-1/n) L ^1/n kg ^-1 and showed a significant positive correlation with the clay content of the soil, while the K _{f (desorption)} ranged from 3.62 to 5.36 µmol ^(1-1/n) L ^1/n kg ^-1 . The K _{f (desorption)} values were higher than their respective K _{f (sorption)} , indicating that aminocyclopyrachlor sorption is reversible, and the fate of this herbicide in the environment can be affected by leaching. Aminocyclopyrachlor was detected at all depths (0-30 cm) in all the studied soils, where leaching was influenced by soil texture. The total herbicide leaching from the sandy clay and clay soils was <0.06%, whereas, ∼3% leached from the loamy sand soil. The results suggest that aminocyclopyrachlor has a high potential of leaching, based on its low sorption and high desorption capacities. Therefore, this herbicide can easily contaminate underground water resources.