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United States Department of Agriculture

Agricultural Research Service

Title: Influence of Soil Aging on Sorption-Desorption and Bioavailability of Simazine

Authors
item Regitano, Jussara - UNIV SAO PAULO BRAZIL
item Koskinen, William
item Sadowsky, Michael - UNIVERSITY OF MINNESOTA

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 21, 2005
Publication Date: January 20, 2006
Citation: Regitano, J.B., Koskinen, W.C., Sadowsky, M.J. 2006. Influence of soil aging on sorption-desorption and bioavailability of simazine. Journal of Agricultural and Food Chemistry. 54:1373-1379.

Interpretive Summary: Characterization of pesticide bioavailability, particularly in aged soils, is of continued interest because this information is necessary for environmental risk assessment of pesticides. The objective of this study was to correlate simazine (a triazine herbicide) residue bioavailability in aged soils, as determined by solvent extraction methods, to simazine mineralization by an simazine-degrading bacterium. We identified a 0.01 M CaCl2/methanol solvent extraction procedure that can characterize simazine bioavailability in dissimilar aged soils, which in turn may be useful to determine bioavailability of other compounds in soils, especially other triazine herbicides. Scientists now have a relatively easy and inexpensive technique to determine the amounts of one class of pesticides, triazines, available for transport, plant uptake, and microbial degradation, particularly in aged soils, information needed for predicting environmental fate and environmental risk assessment.

Technical Abstract: Characterization of pesticide bioavailability, particularly in aged soils, is of continued interest because this information is necessary for environmental risk assessment. Pesticide bioavailability in aged soils has been characterized by a variety of methods with limited success. The objective of this study was to correlate simazine residue bioavailability in aged soils, as determined by solvent extraction methods, to simazine mineralization by a simazine-degrading bacterium. Soils from Brazil, Hawaii, and the Midwest US were treated with UL-ring-labeled 14C-simazine and incubated for up to 8 weeks. At the end of each incubation period, soils were either incubated further, extracted with 0.01 M CaCl2, or extracted with 0.01 M CaCl2/aqueous methanol. Soils were then inoculated with the bacterium Pseudomonas sp. strain ADP, which is capable of rapidly mineralizing the simazine ring. This allowed for the evaluation of the bioavailability of aged simazine residues, without the contribution of simazine desorption from soil. Results of these studies indicated that simazine sorption to soil increased with aging and amounts of simazine in aged soils extracted by 0.01 M CaCl2 and aqueous methanol were correlated to amounts of atrazine mineralized by Pseudomonas sp. strain ADP. Consequently, 0.01 M CaCl2/methanol extractable atrazine in aged soils can be used to estimate bioavailable residues. This technique may be useful to determine bioavailability of other compounds in soils, especially other triazine herbicides.

Last Modified: 7/25/2014
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