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Journal of Environmental Quality Abstract -

Adsorption of Diuron and 2,4,5-T on Soil Particle-Size Separates1


This article in JEQ

  1. Vol. 12 No. 2, p. 195-197
    Received: Mar 22, 1982

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  1. P. Nkedi-Kizza,
  2. P. S. C. Rao and
  3. Jennifer W. Johnson2



Equilibrium isotherms for the adsorption of herbicides, diuron, and 2,4,5-T on whole soil and various-size separates of Webster soil (Typic Haplaquolls) were measured. The Freundlich adsorption coefficient, K, for diuron varied by a factor of about 7 among the different particle-size fractions. However, the sorption coefficient, K, normalized with respect to soil organic carbon (OC) content, denoted as Koc = (K/OC), varied only within a factor of 1.5. For 2,4,5-T herbicide, the Koc values for the silt and clay-size fractions, as well as the whole soil, were essentially identical and about 3 times larger than that for the sand-size fraction. The results suggested that the soil particle-size separates may be grouped into two size classes: “fine” (≤ 50 µm) and “coarse” (2,000-50 µm). For a given pesticide, a specific Koc value may be assigned to each class.

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