Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 3/25/2003
Publication Date: 3/25/2003
Citation: BRESNAHAN, G.A., KOSKINEN, W.C., DEXTER, A.G., COX, L. SORPTION-DESORPTION OF "AGED" ISOXAFLUTOLE AND DIKETONITRILE DEGRADATE IN SOIL. AMERICAN CHEMICAL SOCIETY. 2003. ABSTRACT SPRING. #45. Interpretive Summary:
Technical Abstract: Isoxaflutole is a relatively new herbicide used for the control of weeds in field corn. The objective of this research was to increase the understanding of the behavior and environmental fate of isoxaflutole and a diketonitrile degradate in soil, particularly to determine the strength of sorption to the soil and the importance effects of aging on sorption. Sorption processes directly or indirectly control the amount of herbicide in solution, thereby directly impacting herbicide bioavailability and the persistence and carryover of herbicides. Total 14C-isoxaflutole residue recovery was affected by both soil type and soil pH. Total 14C recovery from sandy loam soil (SL), pH 7.1 and 8.0, was ~85% at wk 0 and at wk 12; in SL soil, pH 5.7, extraction decreased from ~85% at wk 0 to ~65% at wk 12. The largest decrease in total 14C recovery was in silty clay soil (SiCl), pH 7.4, with recovery of 85% at wk 0 and 52% at wk 12. In SL and SiCl soils, 14C isoxaflutole was found to dissipate rapidly after application to soil, at wk 0 recovery ranged from ~42% to 68%, and at wk 12, recovery had decreased to <10%. Decreases in 14C isoxaflutole residues over time in SL and SiCl soils would be consistent with hydrolysis of isoxaflutole and formation of bound DKN residues in the soil. DKN recovery in SiC and SL soil was 41% to 52% at wk 0. At wk 12 in SL soil, pH 7.1 and 8.0, recoveries were similar, ~40%. However, at wk 12 in SL soil, pH 5.7, DKN recovery decreased to ~28%. DKN recovery in SiCl soil at wk 12 was <10%. Total 14C and 14C DKN extractability decreased over time. Increases in sorption of DKN by the SL pH 5.7 soil and the SiCl soil over time, indicate the DKN degradate is tightly bound to the soil and sorption is affected by soil pH and soil type.