Tracer diffusion coefficients in sedimentary rocks: correlation to porosity and hydraulic conductivity

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• 作者：Boving ; Thomas B. ; Grathwohl ; Peter
• 关键词：Diffusion coefficients ; Tortuosity ; Archie's law ; Sedimentary rocks ; Contaminant transport
• 刊名：Journal of Contaminant Hydrology
• 出版年：2001
• 出版时间：December 1, 2001
• 年：2001
• 卷：53
• 期：1-2
• 页码：85-100
• 全文大小：194 K

文摘

Matrix diffusion is an important transport process in geologic materials of low hydraulic conductivity. For predicting the fate and transport of contaminants, a detailed understanding of the diffusion processes in natural porous media is essential. In this study, diffusive tracer transport (iodide) was investigated in a variety of geologically different limestone and sandstone rocks. Porosity, structural and mineralogical composition, hydraulic conductivity, and other rock properties were determined. The effective diffusion coefficients were measured using the time-lag method. The results of the diffusion experiments indicate that there is a close relationship between total porosity and the effective diffusion coefficient of a rock (analogous to Archie's Law). Consequently, the tortousity factor can be expressed as a function of total porosity. The relationship fits best for thicker samples (>1.0 cm) with high porosities (>20 % ), because of the reduced influence of heterogeneity in larger samples. In general, these correlations appear to be a simple way to determine tortuosity and the effective diffusion coefficient from easy to determine rock porosity values.