Experimental Visualization of Solute Transport and Mass Transfer Processes in Two-Dimensional Conductivity Fields with Connected Regions of High Conductivity
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- 作者：Brendan Zinn ; Lucy C. Meigs ; Charles F. Harvey ; Roy Haggerty ; William J. Peplinski ; and Claudius Freiherr von Schwerin
- 刊名：Environmental Science & Technology
- 出版年：2004
- 出版时间：July 15, 2004
- 年：2004
- 卷：38
- 期：14
- 页码：3916 - 3926
- 全文大小：839K
- 年卷期：v.38,no.14(July 15, 2004)
- ISSN：1520-5851
文摘
Solute transport displaying mass transfer behavior (i.e.,tailing) occurs in many aquifers and soils. Spatial patternsof hydraulic conductivity may play a role because ofboth advection and diffusion through isolated low conductivityareas. We demonstrated such processes in laboratoryexperiments designed to visualize solute transport througha thin chamber (40 cm × 20 cm × 0.64 cm thick) packedwith glass beads and containing circular emplacementsof smaller glass beads with lower conductivity. Theexperiments used three different contrasts of conductivitybetween the large-bead matrix and the emplacements,targeting three different regimes of solute transport: lowcontrast, targeting macrodispersion; intermediate contrast,targeting advection-dominated mass transfer betweenthe high-conductivity regions and the emplacements; andhigh contrast, targeting diffusion-dominated masstransfer. Use of a strong light source, a high-resolutionCCD camera, and a colorimetric dye produced images witha spatial resolution of about 400 
m and a concentrationrange of approximately 2 orders of magnitude. These imagesconfirm the existence of the three different regimes, andwe observed tailing driven by both advection and diffusion.Outflow concentration measured by spectrophotometerachieved 3 orders of magnitude in concentration range andshowed good agreement with known models in the caseof dispersion and diffusive mass transfer, with estimatedparameters close to a priori predictions. Existing modelsfor diffusive mass transfer did not fit the breakthrough curvesfrom the intermediate-contrast chamber, but a model ofslow advection through cylinders did. Thus, both breakthroughcurves and chamber images confirm that differentcontrasts in small-scale K lead to different regimes ofsolute transport and thus require different models ofupscaled solute transport.
m and a concentrationrange of approximately 2 orders of magnitude. These imagesconfirm the existence of the three different regimes, andwe observed tailing driven by both advection and diffusion.Outflow concentration measured by spectrophotometerachieved 3 orders of magnitude in concentration range andshowed good agreement with known models in the caseof dispersion and diffusive mass transfer, with estimatedparameters close to a priori predictions. Existing modelsfor diffusive mass transfer did not fit the breakthrough curvesfrom the intermediate-contrast chamber, but a model ofslow advection through cylinders did. Thus, both breakthroughcurves and chamber images confirm that differentcontrasts in small-scale K lead to different regimes ofsolute transport and thus require different models ofupscaled solute transport.