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Tracer transport in fractured crystalline rock: Evidence of nondiffusive breakthrough tailing

Water Resources Research

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and ORCID iD
https://doi.org/10.1029/2000WR900080

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Abstract

Extended tailing of tracer breakthrough is often observed in pulse injection tracer tests conducted in fractured geologic media. This behavior has been attributed to diffusive exchange of tracer between mobile fluids traveling through channels in fractures and relatively stagnant fluid between fluid channels, along fracture walls, or within the bulk matrix. We present a field example where tracer breakthrough tailing apparently results from nondiffusive transport. Tracer tests were conducted in a fractured crystalline rock using both a convergent and weak dipole injection and pumping scheme. Deuterated water, bromide, and pentafluorobenzoic acid were selected as tracers for their wide range in molecular diffusivity. The late time behavior of the normalized breakthrough curves were consistent for all tracers, even when the pumping rate was changed. The lack of separation between tracers of varying diffusivity indicates that strong breakthrough tailing in fractured geologic media may be caused by advective transport processes. This finding has implications for the interpretation of tracer tests designed to measure matrix diffusion in situ and the prediction of contaminant transport in fractured rock.

Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Tracer transport in fractured crystalline rock: Evidence of nondiffusive breakthrough tailing
Series title:
Water Resources Research
DOI:
10.1029/2000WR900080
Volume:
36
Issue:
7
Year Published:
2000
Language:
English
Publisher:
American Geophysical Union
Description:
10 p.
First page:
1677
Last page:
1686