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In situ estimation of the effective chemical diffusion coefficient of a rock matrix in a fractured aquifer

Hydrogeology Journal

By:
, , and
DOI: 10.1007/s10040-007-0255-0

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Abstract

An in situ method of estimating the effective diffusion coefficient for a chemical constituent that diffuses into the primary porosity of a rock is developed by abruptly changing the concentration of the dissolved constituent in a borehole in contact with the rock matrix and monitoring the time-varying concentration. The experiment was conducted in a borehole completed in mudstone on the campus of the University of the Free State in Bloemfontein, South Africa. Numerous tracer tests were conducted at this site, which left a residual concentration of sodium chloride in boreholes that diffused into the rock matrix over a period of years. Fresh water was introduced into a borehole in contact with the mudstone, and the time-varying increase of chloride was observed by monitoring the electrical conductivity (EC) at various depths in the borehole. Estimates of the effective diffusion coefficient were obtained by interpreting measurements of EC over 34 d. The effective diffusion coefficient at a depth of 36 m was approximately 7.8??10-6 m2/d, but was sensitive to the assumed matrix porosity. The formation factor and mass flux for the mudstone were also estimated from the experiment. ?? Springer-Verlag 2007.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
In situ estimation of the effective chemical diffusion coefficient of a rock matrix in a fractured aquifer
Series title:
Hydrogeology Journal
DOI:
10.1007/s10040-007-0255-0
Volume
16
Issue:
4
Year Published:
2008
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Hydrogeology Journal
First page:
629
Last page:
639