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Evaluation of sulfate reduction at experimentally induced mixing interfaces using small-scale push-pull tests in an aquifer-wetland system

Applied Geochemistry

By:
, , , and
DOI: 10.1016/j.apgeochem.2007.06.006

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Abstract

This paper presents small-scale push-pull tests designed to evaluate the kinetic controls on SO42 - reduction in situ at mixing interfaces between a wetland and aquifer impacted by landfill leachate at the Norman Landfill research site, Norman, OK. Quantifying the rates of redox reactions initiated at interfaces is of great interest because interfaces have been shown to be zones of increased biogeochemical transformations and thus may play an important role in natural attenuation. To mimic the aquifer-wetland interface and evaluate reaction rates, SO42 --rich anaerobic aquifer water (??? 100 mg / L SO42 -) was introduced into SO42 --depleted wetland porewater via push-pull tests. Results showed SO42 - reduction was stimulated by the mixing of these waters and first-order rate coefficients were comparable to those measured in other push-pull studies. However, rate data were complex involving either multiple first-order rate coefficients or a more complex rate order. In addition, a lag phase was observed prior to SO42 - reduction that persisted until the mixing interface between test solution and native water was recovered, irrespective of temporal and spatial constraints. The lag phase was not eliminated by the addition of electron donor (acetate) to the injected test solution. Subsequent push-pull tests designed to elucidate the nature of the lag phase support the importance of the mixing interface in controlling terminal electron accepting processes. These data suggest redox reactions may occur rapidly at the mixing interface between injected and native waters but not in the injected bulk water mass. Under these circumstances, push-pull test data should be evaluated to ensure the apparent rate is actually a function of time and that complexities in rate data be considered. ?? 2007 Elsevier Ltd. All rights reserved.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Evaluation of sulfate reduction at experimentally induced mixing interfaces using small-scale push-pull tests in an aquifer-wetland system
Series title:
Applied Geochemistry
DOI:
10.1016/j.apgeochem.2007.06.006
Volume
22
Issue:
12
Year Published:
2007
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Applied Geochemistry
First page:
2618
Last page:
2629