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This article in JEQ

  1. Vol. 28 No. 4, p. 1154-1161
     
    Received: June 28, 1998
    Published: July, 1999


    * Corresponding author(s): s.altfelder@tu-bs.de
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doi:10.2134/jeq1999.00472425002800040014x

Effect of Air-Drying on Sorption Kinetics of the Herbicide Chlortoluron in Soil

  1. Sven Altfelder *,
  2. Thilo Streck and
  3. Jörg Richter
  1. Department of Geoecology, Technical University Carolo-Wilhelmina, Langer Kamp 19 c, 38106 Braunschweig, Germany.

Abstract

Abstract

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.

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