Sorption of Isoxaflutole Diketonitrile Degradate (DKN) and Dicamba in Unsaturated Soil.

Autor: KOSKINEN, WILLIAMC.1 (AUTHOR) koskinen@umn.edu, OCHSNER, TYSONE.1 (AUTHOR), STEPHENS, BRANDONM.2 (AUTHOR), KOOKANA, RAIS.3 (AUTHOR)
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Zdroj: Journal of Environmental Science & Health. Part B. Pesticides, Food Contaminants & Agricultural Wastes. Oct2006, Vol. 41 Issue 7, p1071-1083. 13p. 3 Charts, 4 Graphs.
Abstrakt: When analyzing the sorption characteristics of weakly sorbing or labile pesticides, batch methods tend to yield a high margin of error attributable to errors in concentration measurement and to degradation, respectively. This study employs a recently developed unsaturated transient flow method to determine the sorption of isoxaflutole's herbicidally active diketonitrile degradate (DKN) and dicamba. A 20-cm acrylic column was packed with soils with varied texture that had been uniformly treated with 14 C-labeled chemical. The antecedent solution herbicide in equilibrium with sorbed phase herbicide was displaced by herbicide-free water, which was infiltrated into the column. Sorption coefficients, K d , were obtained from a plot of total herbicide concentration in the soil versus water content in the region where the antecedent solution accumulated. DKN K d values were ∼⃒2–3 times (average K d = 0.71 L kg -1 ) greater using the unsaturated transient flow method as compared to the batch equilibration method in clay loam (K d = 0.33 L kg -1 ), but similar for the two methods in sand (0.12 vs 0.09 L kg -1 ) soils. Dicamba K d values were 3 times greater using the unsaturated transient flow method as compared to the batch equilibration method in the clay loam soil (0.38 vs 0.13 L kg -1 ), however, the K d values were the same for the two methods in the sand (∼⃒0.06 L kg -1 ). This demonstrates that to determine sorption coefficients for labile hydrophilic pesticides, an unsaturated transient flow method may be a suitable alternative to the batch method. In fact, it may be better in cases where transport models have overpredicted herbicide leaching when batch sorption coefficients have been used. [ABSTRACT FROM AUTHOR]
Databáze: GreenFILE
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