Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2003
Publication Date: 5/1/2003
Citation: KOSKINEN, W.C., ANHALT, J.C., SAKALIENE, O., RICE, P.J., MOORMAN, T.B., ARTHUR, E.L. SORPTION-DESORPTION OF "AGED" SULFONYLAMINOCARBONYLTRIAZOLINONE HERBICIDE METABOLITES IN SOIL. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY. 2003. V. 51. p. 3604-3608.
Interpretive Summary: The amount of herbicide in soil that is available for movement to the target pest or for movement into surface and ground waters is controlled by the degree of binding of the chemical to the soil and the rate at which it degrades. Binding and degradation of herbicides are usually characterized for herbicides freshly added to soil, however we have shown in previous studies that the length of time the herbicide is in contact with soil, aging, can affect these processes. While there is limited information on binding and degradation of aged herbicide residues, there is less information on bioavailability and degradation of herbicide breakdown products or metabolites. The present study was conducted to determine the changes in distribution between soil bound and solution phases of two sulfonylaminocarbonyltriazolinone herbicide metabolites, with incubation time. We found that while the herbicide metabolites slowly degraded in soil, the remaining chemical became more tightly bound to the soil. Therefore, the aged residues would be less available for movement to surface and ground waters. These results are further evidence that increases in binding of the pesticide to soil during pesticide aging should be taken into account during characterization of the environmental fate of pesticides and in the development of mathematical models of pesticide degradation and transport.
Technical Abstract: Sorption-desorption processes determine the availability of pesticides and their metabolites in soil for transport, plant uptake, and microbial degradation. These processes are affected by the physical and chemical properties of the soil and the chemical, and for some pesticides and their metabolites, their residence time in the soil. The objective of this study was to characterize sorption-desorption of sulfonylaminocarbonyltriazolinone herbicide metabolites incubated in soils at different soil moisture potentials. Benzenesulfonamide and triazolinone metabolites were incubated in clay loam and loamy sand soils for up to 12 wks at 33 kPa and at water contents equivalent to 50 and 75 % of that at - 33 kPa. Chemicals were extracted sequentially with 0.01 N CaCl2 and aqueous acetonitrile and sorption coefficients were calculated. Aging significantly increased sorption as indicated by increased sorption coefficients. For instance, for benzenesulfonamide and triazolinone remaining after a 12-wk incubation at -33 kPa, Kd values increased by a factor of 3.5 in the clay loam soil and by 5.9 in the loamy sand as compared to freshly treated soils. There was no effect of moisture potential on sorption Kd values. These data show the importance of characterization of sorption-desorption in aged herbicide residues, including metabolites, in soil, particularly in the case of prediction of herbicide residue transport in soil. In this case, potential transport of sulfonylaminocarbonyltriazolinone herbicide metabolites would be over predicted if freshly treated soil Kd values were used to predict transport.