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Title: On the mobilization of metals by CO 2 leakage into shallow aquifers: exploring release mechanisms by modeling field and laboratory experiments

Abstract

The dissolution of CO 2 in water leads to a pH decrease and a carbonate content increase in affected groundwater, which in turn can drive the mobilization of metals from sediments. The mechanisms of metal release postulated in various field and laboratory studies often differ. Drawing primarily on previously published results, we examine contrasting metal mobilization behaviors at two field tests and in one laboratory study, to investigate whether the same mechanisms could explain metal releases in these different experiments. Numerical modeling of the two field tests reveals that fast Ca-driven cation exchange (from calcite dissolution) can explain the release of most major and trace metal cations at both sites, and their parallel concentration trends. The dissolution of other minerals reacting more slowly (superimposed on cation exchange) also contributes to metal release over longer time frames, but can be masked by fast ambient groundwater velocities. Therefore, the magnitude and extent of mobilization depends not only on metal-mineral associations and sediment pH buffering characteristics, but also on groundwater flow rates, thus on the residence time of CO 2-impacted groundwater relative to the rates of metal-release reactions. Sequential leaching laboratory tests modeled using the same metal-release concept as postulated from field experimentsmore » show that both field and laboratory data can be explained by the same processes. Finally, the reversibility of metal release upon CO 2 degassing by de-pressurization is also explored using simple geochemical models, and shows that the sequestration of metals by resorption and re-precipitation upon CO 2 exsolution is quite plausible and may warrant further attention.« less

Authors:
 [1];  [1];  [1];  [1];  [2];  [3];  [1];  [1];  [4]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Southern Company Services, Birmingham AL (United States)
  3. British Geological Survey, Keyworth, Nottingham (United Kingdom)
  4. Electric Power Research Inst., Palo Alto CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Fossil Energy (FE)
OSTI Identifier:
1512097
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Greenhouse Gases: Science and Technology
Additional Journal Information:
Journal Volume: 5; Journal Issue: 4; Journal ID: ISSN 2152-3878
Publisher:
Society of Chemical Industry, Wiley
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; groundwater; carbonic acid; leak; CO 2 sequestration; CCS; CCUS

Citation Formats

Zheng, Liange, Spycher, Nicolas, Varadharajan, Charuleka, Tinnacher, Ruth M., Pugh, John D., Bianchi, Marco, Birkholzer, Jens, Nico, Peter S., and Trautz, Robert C. On the mobilization of metals by CO 2 leakage into shallow aquifers: exploring release mechanisms by modeling field and laboratory experiments. United States: N. p., 2015. Web. doi:10.1002/ghg.1493.
Zheng, Liange, Spycher, Nicolas, Varadharajan, Charuleka, Tinnacher, Ruth M., Pugh, John D., Bianchi, Marco, Birkholzer, Jens, Nico, Peter S., & Trautz, Robert C. On the mobilization of metals by CO 2 leakage into shallow aquifers: exploring release mechanisms by modeling field and laboratory experiments. United States. doi:10.1002/ghg.1493.
Zheng, Liange, Spycher, Nicolas, Varadharajan, Charuleka, Tinnacher, Ruth M., Pugh, John D., Bianchi, Marco, Birkholzer, Jens, Nico, Peter S., and Trautz, Robert C. Thu . "On the mobilization of metals by CO 2 leakage into shallow aquifers: exploring release mechanisms by modeling field and laboratory experiments". United States. doi:10.1002/ghg.1493. https://www.osti.gov/servlets/purl/1512097.
@article{osti_1512097,
title = {On the mobilization of metals by CO 2 leakage into shallow aquifers: exploring release mechanisms by modeling field and laboratory experiments},
author = {Zheng, Liange and Spycher, Nicolas and Varadharajan, Charuleka and Tinnacher, Ruth M. and Pugh, John D. and Bianchi, Marco and Birkholzer, Jens and Nico, Peter S. and Trautz, Robert C.},
abstractNote = {The dissolution of CO2 in water leads to a pH decrease and a carbonate content increase in affected groundwater, which in turn can drive the mobilization of metals from sediments. The mechanisms of metal release postulated in various field and laboratory studies often differ. Drawing primarily on previously published results, we examine contrasting metal mobilization behaviors at two field tests and in one laboratory study, to investigate whether the same mechanisms could explain metal releases in these different experiments. Numerical modeling of the two field tests reveals that fast Ca-driven cation exchange (from calcite dissolution) can explain the release of most major and trace metal cations at both sites, and their parallel concentration trends. The dissolution of other minerals reacting more slowly (superimposed on cation exchange) also contributes to metal release over longer time frames, but can be masked by fast ambient groundwater velocities. Therefore, the magnitude and extent of mobilization depends not only on metal-mineral associations and sediment pH buffering characteristics, but also on groundwater flow rates, thus on the residence time of CO2-impacted groundwater relative to the rates of metal-release reactions. Sequential leaching laboratory tests modeled using the same metal-release concept as postulated from field experiments show that both field and laboratory data can be explained by the same processes. Finally, the reversibility of metal release upon CO2 degassing by de-pressurization is also explored using simple geochemical models, and shows that the sequestration of metals by resorption and re-precipitation upon CO2 exsolution is quite plausible and may warrant further attention.},
doi = {10.1002/ghg.1493},
journal = {Greenhouse Gases: Science and Technology},
number = 4,
volume = 5,
place = {United States},
year = {2015},
month = {4}
}

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Works referenced in this record:

Changes in the chemistry of shallow groundwater related to the 2008 injection of CO2 at the ZERT field site, Bozeman, Montana
journal, December 2009

  • Kharaka, Yousif K.; Thordsen, James J.; Kakouros, Evangelos
  • Environmental Earth Sciences, Vol. 60, Issue 2, p. 273-284
  • DOI: 10.1007/s12665-009-0401-1

A shallow subsurface controlled release facility in Bozeman, Montana, USA, for testing near surface CO2 detection techniques and transport models
journal, December 2009

  • Spangler, Lee H.; Dobeck, Laura M.; Repasky, Kevin S.
  • Environmental Earth Sciences, Vol. 60, Issue 2, p. 227-239
  • DOI: 10.1007/s12665-009-0400-2