Effect of Air-Drying on Sorption Kinetics of the Herbicide Chlortoluron in Soil
- Sven Altfelder *,
- Thilo Streck and
- Jörg Richter
Batch techniques were utilized to investigate sorption kinetics of chlortoluron (3-(3-chlor-p-tolyl)-1,1-dimethylurea) in two field-moist soils, a silt loam (Typic Hapludalf) and a loamy sand (Aquic Haplumbrept), containing 1.1 and 0.7% organic C. To investigate effects of soil pretreatment, a part of both soil samples was initially air-dried. Initially sorption-desorption isotherms were measured using field-moist soils. Both isotherms exhibited pronounced hysteresis. The fit of a nonlinear kinetic two-stage sorption model to the data suggests that hysteresis was caused by nonattainment of equilibrium within the 24-h agitation periods. This hypothesis is supported by the fact that the estimated kinetic parameters were well suited to predict concentration vs. time experiments in both soils. The prediction of sorption-desorption isotherms measured using air-dried soils failed. Compared with the predicted data, adsorption in air-dried soil was increased while desorption hysteresis was less pronounced. Further experiments indicated that changes of soil organic matter (SOM) caused by air-drying were responsible for this effect. Measuring 24-h partitioning coefficients using the air-dried soils, rewetted to field-moisture for varying periods of time, revealed that in the course of 80 h (silt loam) and 500 h (loamy sand) after rewetting, the sorption properties of the air-dried soils were again equal to those of the respective field-moist soils.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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