Zhang Hua, Selim H M
Sturgis Hall, School of Plant, Environmental and Soil Sciences, LSU, Baton Rouge, LA 70803, USA.
J Environ Qual. 2007 Jul 17;36(5):1273-80. doi: 10.2134/jeq2006.0373. Print 2007 Sep-Oct.
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.
由于怀疑胶体促进污染物向地下水的迁移，土壤中胶体的产生和运移具有重要意义。在本研究中，在奥利维尔（细粉质、混合、活性、热性潮湿老成土）和温莎（混合、中温典型潮湿新成土）土柱中研究了胶体的迁移及其对亚砷酸盐[As(III)]运移的影响。将10 mg L(-1) As(III)的0.01 M NaCl输入溶液施加到水饱和的土柱上，然后用去离子水（DIW）淋洗。在As(III)输入和DIW淋洗阶段进行流量中断。随时间监测土柱流出液的浊度、电导率（EC）和pH值。分析了As、Fe和Al的总浓度和溶解浓度。流出液结果表明，当溶液离子强度保持恒定时，胶体促进的迁移对砷的迁移贡献很小。由于输入溶液离子强度的变化，观察到胶体无定形物质的迁移和As(III)迁移的增强。胶体产生的峰值与Fe的峰值浓度一致，表明铁氧化物的迁移和吸附在氧化物表面的As(III)的促进迁移。由于奥利维尔土柱中的流量中断，胶体迁移增强，这表明聚集的胶体颗粒解离缓慢。此外，流出液结果表明有机物对稳定胶体颗粒聚集体有显著影响。
