Sorption of atrazine and trifluralin in relation to the physio-chemical characteristics of selected soils

The sorption of two types of herbicide, atrazine (6-chloro-N2-ethyl-N4 - isopropyl-1,3,5-triazine-2,4-diamine) and trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl- p-toluidine), was studied in four different soils representative of the intensively cultivated soils of the Po Valley (northern Italy). To study the effect of the organic matter content, experiments were carried out with one of the soils after the organic matter had been removed by a sodium hypochlorite treatment. The sorption ability for atrazine and trifluralin was decreased considerably when the soil with high organic matter content was treated with sodium hypochlorite; moreover, the sorption of trifluralin also seems to be influenced by the inorganic components of the soil. In comparison to atrazine, the sorption of trifluralin by the different soils was in all cases very high. Using increasing concentrations of herbicide the sorption coefficient (Kd) for each of the four soils was calculated together with the relative sorption constant (Koc) based on the organic carbon content of the soil. The values of Kf and 1/n in the Freundlich equation for atrazine and trifluralin adsorbed by the four soils were related to the characteristics of the soils. © 1992.