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This article in JEQ

  1. Vol. 36 No. 5, p. 1273-1280
     
    Received: Sept 16, 2006


    * Corresponding author(s): mselim@agctr.lsu.edu
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doi:10.2134/jeq2006.0373

Colloid Mobilization and Arsenite Transport in Soil Columns: Effect of Ionic Strength

  1. Hua Zhang and
  2. H.M. Selim *
  1. Sturgis Hall, School of Plant, Environmental and Soil Sciences, LSU, Baton Rouge, LA 70803. Contribution from Louisiana State Univ. Agric Center as manuscript no. 07-14-0027

Abstract

Colloid generation and transport in soils is of significance because of suspected colloid-facilitated transport of contaminants to the groundwater. In this study, colloid mobilization and its effect on the transport of arsenite [As(III)] were investigated in Olivier (fine-silty, mixed, active, thermic Aquic Fraglossudalfs) and Windsor (mixed, mesic typic Udipsamments) soil columns. Input solution of 10 mg L−1 As(III) in 0.01 M NaCl was applied to water-saturated columns, and followed by leaching with deionized water (DIW). Flow interruptions were performed during the As(III) input and DIW leaching phases. Turbidity, electrical conductivity (EC), and pH of column effluents were monitored with time. Total and dissolved concentrations of As, Fe, and Al were analyzed. Effluent results demonstrated that colloid-facilitated transport contributed little to arsenic movement when the solution ionic strength was maintained constant. Mobilization of colloidal amorphous material and enhanced transport of As(III) were observed as a result of changes in ionic strength of the input solution. The peak of colloid generation coincided with peak concentrations of Fe, suggesting mobilization of Fe oxides and facilitated transport of As(III) adsorbed on oxide surfaces. Colloid mobilization was enhanced due to flow interruption in the Olivier column, which suggests slow dissociation of aggregated colloidal particles. Moreover, effluent results indicate significant effect of organic matter in stabilizing aggregates of colloidal particles.

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Copyright © 2007. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyAmerican Society of Agronomy, Crop Science Society of America, and Soil Science Society of America