Impact of elevated dissolved CO_2 on aquifer water quality

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dc.contributor Zheng, Chunmiao
dc.contributor Tick, Geoffrey R.
dc.contributor Andrus, C. Fred T.
dc.contributor Redwine, James
dc.contributor.advisor Donahoe, Rona Jean
dc.contributor.author Pugh, John David
dc.date.accessioned 2017-03-01T17:23:21Z
dc.date.available 2017-03-01T17:23:21Z
dc.date.issued 2015
dc.identifier.other u0015_0000001_0001904
dc.identifier.other Pugh_alatus_0004D_12290
dc.identifier.uri https://ir.ua.edu/handle/123456789/2330
dc.description Electronic Thesis or Dissertation
dc.description.abstract Carbon capture and storage (CCS), specifically by means of geologic sequestration (GS), is a developing technology to reduce CO2 emissions to the atmosphere. This technology involves separating CO2 from flue gas and transporting the CO2 to underground storage locations that are isolated from the atmosphere. These storage locations are typically permeable and porous geologic formations that are not useful for any other purpose, such as drinking water. Geologic carbon sequestration operated at full-scale will require extensive performance monitoring, including potable groundwater monitoring. However, researchers and regulators do not fully understand what impact elevated CO2 levels would have on groundwater quality in the event that CO2 should leak into an overlying aquifer. The focus of the current study was to thoroughly characterize the properties of a typical Gulf Coast potable aquifer for purposes of performing a controlled CO2 release experiment and to construct coupled geochemical and transport models capable of predicting impacts from CO2 migration into a drinking water aquifer. The aquifer is a methanogenic environment composed primarily of quartz and feldspars, with minor or trace amounts of pyrite, mica, illite, smectite, and kaolinite. The formation water is dominantly Na-HCO3, consistent with the theory and PHREEQC modeling results that suggest aquifer freshening and ion exchange have played dominant roles in determining the present-day dissolved major ion composition. This study also presents the design and implementation of a closed loop pumping and injection system designed to simulate CO2 leakage into a test site aquifer. Process monitoring results indicated that the test was performed with minimal variation in key process parameters, including temperature, pressure and injectate pH. In situ instrumentation deployed in monitoring wells allowed continuous readings of groundwater pH and conductivity, which were critical parameters for evaluating the aquifer response to carbonation and acidification. Successful modeling simulation of the pH response using results from the aquifer testing program suggested that the test was implemented and monitored appropriately and that that future data interpretations and modeling of the field experiment were not compromised by test design. Test results showed that no constituent was mobilized in excess of US EPA maximum contaminant levels, but that many constituents (primarily major and minor cations) were released in a pulse-like response at levels above their baseline concentrations. Dissolution of trace carbonate and pyrite in the aquifer are hypothesized to have triggered cation exchange reactions, a dominant geochemical process affecting major and minor cation behavior in the aquifer. Overall, the test has shown that the migration of carbon dioxide into a drinking water aquifer can mobilize ions into solution, but at levels that may not exceed EPA MCLs under the field conditions tested for this specific system. Data presented here are potentially applicable to assessments across the Gulf Coast, where the potential for deep geologic carbon sequestration and continued reliance upon groundwater resources are high.
dc.format.extent 185 p.
dc.format.medium electronic
dc.format.mimetype application/pdf
dc.language English
dc.language.iso en_US
dc.publisher University of Alabama Libraries
dc.relation.ispartof The University of Alabama Electronic Theses and Dissertations
dc.relation.ispartof The University of Alabama Libraries Digital Collections
dc.relation.hasversion born digital
dc.rights All rights reserved by the author unless otherwise indicated.
dc.subject.other Geochemistry
dc.subject.other Geology
dc.title Impact of elevated dissolved CO_2 on aquifer water quality
dc.type thesis
dc.type text
etdms.degree.department University of Alabama. Dept. of Geological Sciences
etdms.degree.discipline Geology
etdms.degree.grantor The University of Alabama
etdms.degree.level doctoral
etdms.degree.name Ph.D.


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