Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2006
Publication Date: 5/11/2006
Citation: Koskinen, W.C., Calderon, M.J., Rice, P.J., Cornejo, J. 2006. Sorption-desorption of flucarbazone and propoxycarbazone and their benzenesulfonamide and triazolinone metabolites in two soils. Pest Management Science. 62:598-602.
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 is arguably the most important process, as it directly or indirectly controls all other processes. While there is limited information on binding of the newer herbicides, there is very little information on binding of herbicide breakdown products or metabolites. The present study was conducted to determine the binding of two newer use herbicides, sulfonylaminocarbonyltriazolinones, and their principle metabolites. We found that binding of for all four chemicals was greater in soils, which had greater organic carbon and clay contents as compared to sandy soils. Binding of the metabolite could not be predicted from information about binding of the corresponding herbicide. These data show the importance of characterization of binding of herbicide residues (including breakdown products) 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 parent chemical soil sorption values were used to predict transport. These results will aid scientists who are developing mathematical models of pesticide degradation and transport in soil. They show that scientists need to make their models more flexible for binding characterization, which in turn would make the models more accurate in predicting potential movement of herbicides to surface and ground waters.
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. While sorption-desorption of many herbicides has been characterized, very little work in this area has been done on herbicide metabolites in soil. The objective of this study was to characterize sorption-desorption of two sulfonylaminocarbonyltriazolinone herbicides, flucarbazone and propoxycarbazone, and their benzenesulfonamide and triazolinone metabolites in two soils with different physical and chemical properties. Kf values for all four chemicals were greater in the clay loam soil, which had greater organic carbon and clay contents as compared to the loamy sand. Kf-oc ranged from 29 to 119 for herbicides and from 42 to 84 for the metabolites. Desorption was hysteretic in every case. Lower desorption in the more sorptive system might indicate that hysteresis can be attributed to irreversible binding of the molecules to soil surfaces. These data show the importance of characterization of both sorption and desorption of herbicide residues 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 parent chemical soil sorption values were used to predict transport.