Metal Release from Sandstones under Experimentally and Numerically Simulated CO2 Leakage Conditions

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• 作者：Katie Kirsch ; Alexis K. Navarre-Sitchler ; Assaf Wunsch ; John E. McCray
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：February 4, 2014
• 年：2014
• 卷：48
• 期：3
• 页码：1436-1442
• 全文大小：440K
• ISSN：1520-5851

文摘

Leakage of CO₂ from a deep storage formation into an overlying potable aquifer may adversely impact water quality and human health. Understanding CO₂-water-rock interactions is therefore an important step toward the safe implementation of geologic carbon sequestration. This study targeted the geochemical response of siliclastic rock, specifically three sandstones of the Mesaverde Group in northwestern Colorado. To test the hypothesis that carbonate minerals, even when present in very low levels, would be the primary source of metals released into a CO₂-impacted aquifer, two batch experiments were conducted. Samples were reacted for 27 days with water and CO₂ at partial pressures of 0.01 and 1 bar, representing natural background levels and levels expected in an aquifer impacted by a small leakage, respectively. Concentrations of major (e.g., Ca, Mg) and trace (e.g., As, Ba, Cd, Fe, Mn, Pb, Sr, U) elements increased rapidly after CO₂ was introduced into the system, but did not exceed primary Maximum Contaminant Levels set by the U.S. Environmental Protection Agency. Results of sequential extraction suggest that carbonate minerals, although volumetrically insignificant in the sandstone samples, are the dominant source of mobile metals. This interpretation is supported by a simple geochemical model, which could simulate observed changes in fluid composition through CO₂-induced calcite and dolomite dissolution.