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This article in JEQ

  1. Vol. 2 No. 4, p. 428-433
    Received: Oct 3, 1972

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Experimental and Predicted Movement of Three Herbicides in a Water-Saturated Soil1

  1. J. M. Davidson and
  2. J. R. McDougal2



The equilibrium adsorption characteristics of 1,1-dimethyl-3-(a,a,a-trifluoro-m-tolyl) urea (fluometuron), 4-amino-3,5,6-trichloropicolinic acid (picloram), and 2,4-bis(isopropylamino)-6-(methylthio)-s-triazine (prometryne) on Ca-saturated Norge loam soil were measured and were found to fit the Freundlich equation. A solution of each herbicide was displaced through a water-saturated colume of Norge loam soil at various average pore-water velocities (5.6 to 0.57 cm/hour) and effluent samples evaluated to determine the importance of adsorption kinetics to the mobility of the herbicide. The displacement of each herbicide through the soil was significantly influenced by the average pore-water velocity. The use of a kinetic adsorption model in a convective transport equation did not adequately predict the shape of the effluent concentration distribution at the high pore-water velocities, but did give the left-hand shift exhibited by the data. The tailing noted in all the herbicide effluent concentration distributions resulted primarily from the nonsingularity between the adsorption-desorption process. Equilibrium adsorption and desorption isotherms were measured for picloram on Ca-saturated Norge loam soil.

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