Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2002
Publication Date: 8/8/2002
Citation: KOSKINEN, W.C., RICE, P.J., ANHALT, J.C., SAKALIENE, O., MOORMAN, T.B., ARTHUR, E.L. SORPTION-DESORPTION OF "AGED" SULFONYLAMINOCARBONYLTRIAZOLINONE RBICIDES IN SOIL. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY. 2002. V. 50. p. 5368-5372.
Interpretive Summary: The amount of pesticide 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 pesticides are usually characterized for pesticides freshly added to soil, however we have shown in previous studies that the length of time the pesticide is in contact with soil, aging, can affect these processes. There is limited information on binding and degradation of aged pesticide residues and there is no information on bioavailability and degradation of the sulfonylaminocarbonyltriazolinone class of herbicides. The present study was conducted to determine the changes in distribution between soil bound and solution phases of two sulfonylaminocarbonyltriazolinone class of herbicides with incubation time. We found that while the herbicides 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 interactions of pesticides with soil determine the availability of pesticides in soil for transport, plant uptake, and microbial degradation. These interactions are affected by the physical and chemical properties of the pesticide and soil, and for some pesticides, their residence time in the soil. The objective of this study was to characterize sorption-desorption of two sulfonylaminocarbonyltriazolinone herbicides incubated in soils at different soil moisture potentials. The chemicals 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. Soil moisture had little or no effect on degradation of both compounds. Aging significantly increased sorption as indicated by increased sorption coefficients. For instance, for sulfonylaminocarbonyltriazolinone remaining after a 12-wk incubation at -33 kPa, Kd increased by a factor of 4.5 in the clay loam soils and by 6.6 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 in soil, particularly in the case of prediction of herbicide transport in soil. In this case, potential transport of sulfonylaminocarbonyltriazolinone herbicides would be over predicted if freshly treated soil Kd values were used to predict transport.