About Us | Help Videos | Contact Us | Subscriptions

Soil Science Society of America Journal Abstract -

Sorption of Bromacil, Chlortoluron, and Diuron by Soils1


This article in SSSAJ

  1. Vol. 50 No. 6, p. 1467-1471
    Received: Nov 1, 1985

Request Permissions

  1. Yousef A. Madhun,
  2. V. H. Freed,
  3. J. L. Young and
  4. S. C. Fang2



Sorption of bromacil (5-bromo-3-sec-butyl-6-methyluracil), chlortoluron [3-(3-chloro-4-methylphenyl),1,1-dimethylurea], and diuron [3-(3,4-dichlorophenyl)1,1-dimethylurea] by soils containing contrasting organic carbon (OC) content was studied. The sorptive capacity of the soils was assessed at 4 and 25°C by the batch equilibrium procedure over a broad range of aqueous phase herbicide concentrations. The herbicides showed the following order of increasing tendency to be sorbed: diuron > chlortoluron > bromacil. Sorption constants (Kf) were from 50- to 120-fold higher for the organic soil than for the loamy sand soil, reflecting sorption dependence on soil OC. This variation in Kf was reduced to less than twofold variation in Koc by normalizing sorption to OC. Although sorption was higher at 4 than at 25°C, the difference was only minor at this temperature range. The isosteric heats of sorption (δHs) were relatively small and exothermic, suggesting the involvement of entropy driven mechanism. Water solubility (S) and octanol-water partition coefficient (Kow) of the herbicides were determined and used to derive equations for estimating Koc with r2 ≥0.989. The practical utility of these correlations is that they allow reasonable estimates of Koc from more easily determined molecular parameters.

  Please view the pdf by using the Full Text (PDF) link under 'View' to the left.

Copyright © . Soil Science Society of America