Coupled Diffusion and Abiotic Reaction of Trichlorethene in Minimally Disturbed Rock Matrices

Laboratory experiments were performed using minimally disturbed sedimentary rocks to measure the coupled diffusion and abiotic reaction of trichloroethene (TCE) through rock core samples. Results showed that, for all rock types studied, TCE dechlorination occurred, as evidenced by generation of acet...

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Bibliographic Details
Published in:Environmental science & technology 2013-05, Vol.47 (9), p.4291-4298
Main Authors: Schaefer, Charles E, Towne, Rachael M, Lippincott, David R, Lazouskaya, Volha, Fischer, Timothy B, Bishop, Michael E, Dong, Hailiang
Format: Article
Language:English
Subjects:
Applied sciences
Biodegradation
Chemical reactions
Diffusion
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
Exact sciences and technology
Geochemistry
Geology
Groundwaters
Iron
Kinetics
Natural water pollution
Oxidation
Pollution
Pollution, environment geology
Rocks
Scanning electron microscopy
Sedimentary geology
Trichloroethylene - chemistry
Water treatment and pollution
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Summary:Laboratory experiments were performed using minimally disturbed sedimentary rocks to measure the coupled diffusion and abiotic reaction of trichloroethene (TCE) through rock core samples. Results showed that, for all rock types studied, TCE dechlorination occurred, as evidenced by generation of acetylene, ethene, and/or ethane daughter products. First-order bulk reaction rate constants for TCE degradation ranged from 8.3 × 10–10 to 4.2 × 10–8 s–1. Observed reaction rate constants showed a general correlation to the available ferrous iron content of the rock, which was determined by evaluating the spatial distribution of ferrous iron relative to that of the rock porosity. For some rock types, exposure to TCE resulted in a decrease in the effective diffusivity. Scanning electron microscopy (SEM) indicated that the decrease in the effective diffusivity was due to a decrease in the porosity that occurred after exposure to TCE. Overall, these coupled diffusion and reaction results suggest that diffusion of TCE into rock matrices as well as the rate and extent of back-diffusion may be substantially mitigated in rocks that contain ferrous iron or other naturally occurring reactive metals, thereby lessening the impacts of matrix diffusion on sustaining dissolved contaminant plumes in bedrock aquifers.
ISSN:0013-936X
1520-5851
DOI:10.1021/es400457s