Adsorption and leaching of trifluralin, metolachlor, and metribuzin in a commerce soil.

Trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine], metolachlor [2-chloro-N-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) aceta mide], and metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4,-triazin-5(4H) -one] were selected to study adsorption and leaching potentials related to pollution on Commerce silty clay loam soil near Baton Rouge, Louisiana. At a I:10 soil/water ratio, the Koc values for trifluralin, metolachlor and metribuzin were 875, 135, and 96, respectively. Leaching of these herbicides was evaluated in soil columns (5.4 cm i.d. x 26 cm long). Total recoveries of the herbicides applied to the soil column were 73.1% +/- 4.1%. When the soil columns were leached with three pore volumes of water, the distributions of trifluralin in soil and leachate were 99.993% and 0.007% of the total recoveries, respectively. The distributions of metolachlor was 65.27% in soil and 34.7% in leachate. The distributions of metribuzin was 11.42% in soil and 88.58% in leachate. The results showed that metolachlor and metribuzin were readily leached, while trifluralin was strongly adsorbed to soil. Leaching of three herbicides in the soil column followed the leaching trends of their calculated leaching indices 1.41 x 10(4), 4.18 x 10(6), and 3.38 x 10(8) for trifluralin, metolachlor, and metribuzin, respectively. The results of the study demonstrated the potential of pollution for metolachlor and metribuzin to be leached into the ground water in soils with shallow aquifer.