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Acifluorfen sorption and sorption kinetics in soil

Locke, M.A., Gaston, L.A., Zablotowicz, R.M.
Journal of agricultural and food chemistry 1997 v.45 no.1 pp. 286-293
acifluorfen, sorption, kinetics, microbial activity, biodegradation, calcium chloride, textural soil types
Factors which influence kinetics of sorption for acifluorfen, a postemergence herbicide, in soil were evaluated. Twelve soils of varying characteristics were used in this study. Sorption kinetics experiments with 5.86 micromolar 14C-labeled (19.6 Bq mL-1) acifluorfen were conducted for equilibration times up to 96 h. Sorption was rapid for all soils, and most soils reached a pseudo-equilibrium after 24-48 h of equilibration. Apparent sorption increased at later times, possibly reflecting sorption of acifluorfen or metabolites, since acifluorfen is subject to biotransformation. Further investigation comparing sorption at 4 and 25 degrees C indicated that microbial metabolism was occurring for some soils at equilibration times longer than 24-48 h. Aminoacifluorfen was observed in methanol extracts of soils equilibrated 96 h. Soils were equilibrated for 24 h with 14C-labeled acifluorfen (2.6-65.8 micromolar, 19.5 Bq mL-1) to obtain sorption isotherms. Capacity for acifluorfen sorption in these soils generally increased with increasing soil organic carbon content, cation exchange capacity, and soil acidity.