Potential Risks of Freshwater Aquifer Contamination with Geosequestration
- Duke Univ., Durham, NC (United States); Duke University
Substantial leakage of CO2 from deep geological strata to shallow potable aquifers is likely to be rare, but chemical detection of potential leakage nonetheless remains an integral component of any safe carbon capture and storage system. CO2 that infiltrates an unconfined freshwater aquifer will have an immediate impact on water chemistry by lowering pH in most cases and by altering the concentration of total dissolved solids. Chemical signatures in affected waters provide an important opportunity for early detection of leaks. In the presence of CO2, trace elements such as Mn, Fe, and Ca can increase by an order of magnitude or more above control concentrations within 100 days. Therefore, these and other elements should be monitored along with pH as geochemical markers of potential CO2 leaks. Dissolved inorganic carbon and alkalinity can also be rapidly responsive to CO2 and are stable indicators of a leak. Importantly, such changes may be detectable long before direct changes in CO2 are observed. The experimental results also suggest that the relative severity of the impact of leaks on overlying drinking-water aquifers should be considered in the selection of CO2 sequestration sites. One primary selection criteria should be metal and metalloid availability, such as uranium and arsenic abundance, to carefully monitor chemical species that could trigger changes above maximum contaminant levels (MCLs). Overall, the risks of leakage from underground CO2 storage are real but appear to be manageable if systems are closely monitored.
- Research Organization:
- Duke Univ., Durham, NC (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FE0002197
- OSTI ID:
- 1127073
- Country of Publication:
- United States
- Language:
- English
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