Stream-Subsurface Exchange of Zinc in the Presence of Silica and Kaolinite Colloids

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• 作者：Jianhong Ren and Aaron I. Packman
• 刊名：Environmental Science & Technology
• 出版年：2004
• 出版时间：December 15, 2004
• 年：2004
• 卷：38
• 期：24
• 页码：6571 - 6581
• 全文大小：362K
• 年卷期：v.38,no.24(December 15, 2004)
• ISSN：1520-5851

文摘

The mobility of sorbing contaminants in surface watersoften depends strongly on associations with sediments,including both fine suspended particles and stationary bedsediments. Hydrodynamic flow coupling causes anexchange of dissolved and suspended substances betweenstreams and underlying pore waters (hyporheic exchange).As a result, the fate of many pollutants is expected tobe greatly influenced by the flux of colloids and contaminantsacross the stream-subsurface interface and the interactionsof both types of substances with the bed sediments.Herein, we present experimental results on the stream-subsurface exchange of zinc in the presence of colloidalsilica and kaolinite in a laboratory flume. We also apply aprocess-based theoretical model to predict the coupledtransport of colloids and reactive solutes. Model inputparameters were obtained using independent batch andcolumn experiments. Zinc immobilization in the bed wasfound to be significantly greater in the presence ofkaolinite than in the presence of colloidal silica. Modelpredictions indicated that there were two distinct reasonsfor the greater zinc immobilization in the presence ofkaolinite: zinc sorbed more strongly to kaolinite than tosilica, and kaolinite particles also deposited more readilyin the streambed than did silica colloids. Model simulationswere found to be highly dependent on the colloid sizedistribution. When the colloids had a bimodal distribution,colloidal-phase contaminant transport occurred primarilyon the finer fraction, but bulk colloid deposition was dominatedby removal of the coarser fraction.