Kinetic control of oxidation state at thermodynamically buffered potentials in subsurface waters

Washington, John W.; Endale, Dinku M.; Samarkina, Lidia P.; Chappell, Kari E.

doi:10.1016/j.gca.2004.06.001

Cited by 26 publications

(45 citation statements)

References 42 publications

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“…This belief is not, however, supported by Washington et al (2004), who characterized the redox chemistry of three shallow aquifers in Georgia in exquisite detail. Their study showed that redox pairs aggregated into two clusters in local partial equilibrium, an upper pe cluster containing N, Fe, and O 2 /H 2 O 2 couples, and a lower pe cluster consisting of C, S, and H couples.…”

Section: Appendix B: Evaluation Of Groundwater Redox Statementioning

confidence: 92%

“…Caution must be exercised in adopting this assumption, as it is well-known that detrital minerals, e.g., feldspars, and organic matter present in aquifer rocks may be subject to diagenesis over periods up to millions of years, and rarely achieve thermodynamic equilibrium. Furthermore, many shallow groundwaters are out of equilibrium with respect to redox reactions (Lindberg and Runnels 1984;Stefansson et al 2005;Washington et al 2004). The role that a potential disequilibrium state plays with respect to redox potential is discussed further in Appendix B.…”

Section: Environmental Protection Agency 2004)mentioning

confidence: 99%

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Evaluation of Potential Changes in Groundwater Quality in Response to CO2 Leakage from Deep Geologic Storage

et al. 2010

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Concern has been expressed that carbon dioxide (CO 2 ) leaking from deep geological storage could adversely impact water quality in overlying potable aquifers by mobilizing hazardous trace elements. In this article, we present a systematic evaluation of the possible water quality changes in response to CO 2 intrusion into aquifers currently used as sources of potable water in the United States. The evaluation was done in three parts. First, we developed a comprehensive geochemical model of aquifers throughout the United States, evaluating the initial aqueous abundances, distributions, and modes of occurrence of selected hazardous trace elements in a large number of potable groundwater quality analyses from the National Water Information System (NWIS) database. For each analysis, we calculated the saturation indices (SIs) of several minerals containing these trace elements. The minerals were initially selected through literature surveys to establish whether field evidence supported their postulated presence in potable water aquifers. Mineral assemblages meeting the criterion of thermodynamic saturation were assumed to control the aqueous concentrations of the hazardous elements at initial system state as well as at elevated CO 2 concentrations caused by the ingress of leaking CO 2 . In the second step, to determine those hazardous trace elements of greatest concern in the case of CO 2 leakage, we conducted thermodynamic calculations to predict the impact of increasing CO 2 partial pressures on the solubilities of the identified trace element mineral hosts. Under reducing conditions characteristic of many groundwaters, the trace elements of greatest concern are arsenic (As) and lead (Pb). In the final step, a series of reactive-transport simulations was performed to investigate the chemical evolution of aqueous As and Pb after the intrusion of CO 2 from a storage reservoir into a shallow confined groundwater resource. Results from the reactive-transport model suggest that a significant increase of aqueous As and Pb concentrations may occur in response to CO 2 intrusion, but that the maximum concentration values remain below or close to specified maximum contaminant levels (MCLs). Adsorption/desorption from mineral surfaces may strongly impact the mobilization of As and Pb.

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Section: Appendix B: Evaluation Of Groundwater Redox Statementioning

confidence: 92%

Section: Environmental Protection Agency 2004)mentioning

confidence: 99%

Evaluation of Potential Changes in Groundwater Quality in Response to CO2 Leakage from Deep Geologic Storage

et al. 2010

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“…All aquifers are in a stable state of redox disequilibria [33,34]. However, the redox environment can be used to predict [35,36] the equilibrium ion concentration ranges as the redox environment is changed.…”

Section: Zvm Treatmentmentioning

confidence: 99%

Sustainable Zero-Valent Metal (ZVM) Water Treatment Associated with Diffusion, Infiltration, Abstraction, and Recirculation

Antia¹

2010

Sustainability

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Socio-economic, climate and agricultural stress on water resources have resulted in increased global demand for water while at the same time the proportion of potential water resources which are adversely affected by sodification/salinisation, metals, nitrates, and organic chemicals has increased. Nano-zero-valent metal (n-ZVM) injection or placement in aquifers offers a potential partial solution. However, n-ZVM application results in a substantial reduction in aquifer permeability, which in turn can reduce the amount of water that can be abstracted from the aquifer. This study using static diffusion and continuous flow reactors containing n-ZVM and m-ZVM (ZVM filaments, filings and punchings) has established that the use of m-ZVM does not result in a reduction in aquifer permeability. The experimental results are used to design and model m-ZVM treatment programs for an aquifer (using recirculation or static diffusion). They also provide a predictive model for water quality associated with specific abstraction rates and infiltration/injection into an aquifer. The study demonstrates that m-ZVM treatment requires 1% of the weight required for n-ZVM treatment for a specific flow rate. It is observed that 1 t Fe 0 will process 23,500 m 3 of abstracted or infiltrating water. m-ZVM is able to remove >80% of nitrates from flowing water and adjust the water composition (by reduction) in an aquifer to optimize removal of nitrates, metals and organic compounds. The experiments demonstrate that ZVM treatment of an aquifer can be used to reduce groundwater salinity by 20 -> 45% and that an aquifer remediation program can be designed to desalinate an aquifer. Modeling indicates that widespread application of m-ZVM water treatment may reduce global socio-economic, climate and agricultural stress on water resources. The rate of oxygen formation during water reduction OPEN ACCESSSustainability 2010, 2 2989[by ZVM (Fe 0 , Al 0 and Cu 0 )] controls aquifer permeability, the associated aquifer pH, aquifer Eh and the degree of water treatment that occurs.

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“…In addition, as discussed further below, it has been clearly established that complete redox equilibrium in shallow groundwater systems is rarely, if ever, achieved (e.g., Lindberg and Runnels, 1984;Washington et al, 2004;Stefansson et al, 2005). Furthermore, many of the trace elements and some of the major constituents can undergo reduction or oxidation in response to periodic infiltration of rainfall, which transports not only dissolved constituents already present in the rain (Na , which have been subject to evapotranspiration, but also dissolved inorganic constituents and organic matter from the overlying soil zone.…”

Section: Thermodynamic Evaluation Of Baseline Groundwater Compositionmentioning

confidence: 99%

“…Following Lindberg and Runnels (1984), therefore, attempts have been made to chemically analyze dissolved redox pairs in groundwaters (e.g., Washington et al, 2004;Stefansson et al, 2005), and then calculate the apparent redox potential for each pair. As expected, the analyzed redox pairs yield disparate redox "potentials."…”

Section: Thermodynamic Evaluation Of Baseline Groundwater Compositionmentioning

confidence: 99%

Groundwater Chemistry Changes as a Result of CO2 Injection at the ZERT Field Site in Bozeman, Montana

Apps¹,

Birkhölzer²,

Spycher³

et al. 2009

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Kinetic control of oxidation state at thermodynamically buffered potentials in subsurface waters

Cited by 26 publications

References 42 publications

Evaluation of Potential Changes in Groundwater Quality in Response to CO2 Leakage from Deep Geologic Storage

Evaluation of Potential Changes in Groundwater Quality in Response to CO2 Leakage from Deep Geologic Storage

Sustainable Zero-Valent Metal (ZVM) Water Treatment Associated with Diffusion, Infiltration, Abstraction, and Recirculation

Groundwater Chemistry Changes as a Result of CO2 Injection at the ZERT Field Site in Bozeman, Montana

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