Dissolved Gases as Partitioning Tracers for Determination of Hydrogeological Parameters

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• 作者：Vijay M. Vulava ; Evan B. Perry ; Christopher S. Romanek ; and John C. Seaman
• 刊名：Environmental Science & Technology
• 出版年：2002
• 出版时间：January 15, 2002
• 年：2002
• 卷：36
• 期：2
• 页码：254 - 262
• 全文大小：121K
• 年卷期：v.36,no.2(January 15, 2002)
• ISSN：1520-5851

文摘

In this study, dissolved Kr and SF₆ gases were used todetermine various hydrogeological parameters of laboratorycolumns under water-saturated and partially saturatedconditions as a function of the flow velocity. The dissolvedgases behaved conservatively in saturated columns butwere significantly retarded in unsaturated conditions as adirect function of the Henry's law constant (K_H) and theratio of column pore spaces filled with air and water(V_g/V_w). Lower aqueous diffusion coefficients for SF₆ comparedto that for Kr also resulted in significant rate-limitedmass transport across gas-water interface. This effectwas exacerbated at higher flow velocities as was indicatedby the asymmetric shape of breakthrough curves, moreso in the case of SF₆. A nonequilibrium advective-dispersivetransport model accurately described tracer breakthroughand was used to estimate parameters such as finalV_g/V_w under partially saturated conditions and partitioningrates. Internally consistent model results were obtainedfor both dissolved gases despite the wide range in physicalproperties (e.g., K_H and aqueous diffusion coefficients),suggesting that dissolved Kr and SF₆ may be used inconjunction to delineate and validate aquifer characteristicssimultaneously from a single pulse injection of thetracer.