Modeling of Simultaneous Exchange of Colloids and Sorbing Contaminants between Streams and Streambeds

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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：May 15, 2004
• 年：2004
• 卷：38
• 期：10
• 页码：2901 - 2911
• 全文大小：281K
• 年卷期：v.38,no.10(May 15, 2004)
• ISSN：1520-5851

文摘

Contaminant transport in streams can be significantlymodified by both stream-subsurface exchange and thepresence of colloidal particles, but the interaction of theseeffects is not well understood. Exchange with the hyporheiczone exposes contaminants to surface-chemicalreactions with streambed sediments, while colloidalparticles have a large reactive surface area that allowsthem to carry pollutants that would otherwise be transportedprimarily as dissolved species. A new theoretical modelis developed to predict the role of colloids in mediatingadvective contaminant exchange between streams andstreambeds. Bedform-induced pumping theory is appliedto model physical transport, and colloid filtration and reversiblecontaminant sorption are used to calculate the localdistributions of colloids and contaminants within thestreambed. Residence time functions of both colloids andcontaminants in the bed are then used to link contaminantconcentrations in the pore water and streamwater. Modelsimulations indicate that, under conditions of low colloidfiltration and strong contaminant sorption to colloids,contaminants are mobilized by colloids and there is lessretention of contaminants in the streambed. This is the caseof "colloid-facilitated contaminant transport" commonlyconsidered in groundwater transport. On the other hand,when colloid filtration is high and contaminants still sorbstrongly to colloids, contaminant mobility decreases and thereis greater contaminant retention in the streambed. Weterm this case "colloid-impeded contaminant transport".Thus, we find that a variety of contaminant transport behaviorcan occur depending on the concentration and mobilityof suspended particles in the system and the relative affinityof contaminants for colloids and other solid phases.