Potential impacts of CO₂ leakage on groundwater quality of overlying aquifer at geological carbon sequestration sites: A review and a proposed assessment procedure

Abstract

One of the risks of geologic carbon sequestration (GCS) is the leakage of injected CO 2 into overlying groundwater resources, resulting in potential deterioration of the quality of the groundwater due to the increase in acidity, the release of trace metals and organic compounds, and potential changes in microbial activities. A large number of studies have been conducted to evaluate various aspects of the impact of CO 2 leakage on overlying aquifers using natural analog, laboratory experiments, field tests, and numerical models. In this paper, we conducted an exhaustive review of the published work, focusing on the statistical assessment of the risk posed by the trace elements including Pb, As, Cd, Ba, and U and identifying the knowledge gaps. Key observations from the review include the following: (1) Pb, As, and U are metals of primary concern because multiple cases showed their concentration higher than maximum contaminant level (MCL) or other regulatory standards, (2) carbonate aquifers seemed more vulnerable to Pb and As contamination but not to U, (3) Cd and Ba are less a concern, only one case showed Cd/Ba concentration higher than MCL, (4) none of the field studies showed the concentrations of Pb and As higher than MCL, although one push-pull field test showed the concentration of U higher than MCL, (5) the order of aggressiveness in terms of releasing trace metals was determined to be as follows: batch experiment > column experiment > field test, and (6) there is no clear correlation between metal release and type of sediments, type of aquifer, the content of carbonate and clay. Evaluation likely has to be done on a case-by-case basis. For further operations of CO 2 storage overview and screening of potential sites, we suggest the use of an eight-step environmental risk assessment procedure comprising laboratory experiment, screening modeling work, and field testing for assessing the vulnerability of the overlying aquifers to degradation from CO 2 leakage from the GCS site.

Trends in Research and Development for CO2 Capture and Sequestration

“…Fault planes or fracture networks near the injection zone increase the possibility of gaps, which would be potentially dangerous to life in the surrounding area. CO 2 can potentially migrate into shallow groundwater aquifers and compromise water quality by releasing trace metals such as Sr, Zn, Co, and Ba and organic compounds and/or change the water’s pH. , …”

“…CO 2 can potentially migrate into shallow groundwater aquifers and compromise water quality by releasing trace metals such as Sr, Zn, Co, and Ba and organic compounds and/or change the water's pH. 178,179 Deep coal seams that are not economically viable sources for coal mining are generally used for sequestration of CO 2 . Despite the many advantages of these sites, the injected CO 2 may chemically and physically alter the coal matrix and induce its swelling and mobilization of polycyclic aromatic hydrocarbons (PAHs) in the coal seam.…”

New Insights on Catalytic Valorization of Carbon Dioxide by Conventional and Intensified Processes

“…However, it is important to consider the limited storage capacity, as well as possible leakage of CO 2 , leading to groundwater contamination. 23 Alternative industrial methods to deal with the captured CO 2 will undoubtedly be required in the near future. Additionally, it is true that merely sequestrating CO 2 in the ground is a tremendous waste of a resource that could be better used for different applications.…”

“…Nevertheless, an important question remains: what should be done with the captured CO 2 ? Carbon sequestration, a technology that allows CO 2 to be trapped into the rock layers of the ground ,− is one possible approach. Shales, coals, or saline aquifers are examples of rock formations where CO 2 sequestration is possible.…”

Downwind dispersion of CO2 from a major subsea blowout in shallow offshore waters

“…Offshore geologic carbon sequestration (GCS) largely avoids a variety of concerns related to onshore GCS in the United States, for example, potential for impacting groundwater quality in the case of leakage of CO 2 into underground sources of drinking water, 1,2 inducing seismicity that is felt and/or damaging to houses and buildings, 3,4 and securing subsurface storage rights from a potential multitude of property owners 5,6 . In addition, a great deal of capacity for GCS has been identified in the offshore waters of the United States., for example, in the near offshore waters of the Texas Gulf Coast where there are numerous existing industrial CO 2 sources and networks of transportation infrastructure 7,8 …”