Environmental Controls of Cadmium Desorption during CO₂ Leakage

Abstract

Geologic carbon sequestration represents a promising option for carbon mitigation. Injected CO(2), however, can potentially leak into water systems, increase water acidity, and mobilize metals. This study used column experiments to quantify the effects of environmental controls on cadmium desorption during CO(2) leakage in subsurface systems without ambient flow. Results show that fast leakage rates are responsible for earlier and larger amounts of Cd desorption. Long weathering time of Cd laden clay leads to low Cd desorption. Calcite content as low as 10% can mitigate the effect of pH reduction and result in zero Cd desorption. Increasing the salinity of the leaking fluid has a relatively minor effect, primarily due to the offsetting impacts of an increased extent of ion exchange and the decrease in CO(2) solubility (and therefore acidity). This work systematically quantifies, for the first time, the effects of environmental controls on Cd desorption and points to key parameters for risk assessment associated with metal mobilization during CO(2) leakage.

Developments since 2005 in understanding potential environmental impacts of CO2 leakage from geological storage

“…This means that dissolution of calcite induced by CO 2 is dissociated from potential remobilization of sorbed Cd and Cu. The role of calcite in Cd immobilization onto sediment (illite and calcite) was also confirmed by Frye et al (2012), who concluded that calcite contents as low as 10% can mitigate the effect of pH reduction and that Cd release and sorption is strongly pH-dependent.…”

“…This can be explained by a significant change in the surface charge of the goethite after CO 2 intrusion, assuming that surface charge is strongly dependent on pH as it is widely described in the literature. Frye et al (2012) investigated the effect of salinity on desorption behaviour in a column experiment. Besides a higher solubility of CO 2 in low ionic strength solutions with a lower pH, they showed that desorption is enhanced by high ionic strength.…”

Self‐healing of cement fractures under dynamic flow of CO2‐rich brine

“…Possible leakage pathways include annular spaces or degraded zones between cement and rock, between the cement and the casing, or the cement plug itself [Celia and Bachu, 2003]. Leakage of CO 2 through these pathways into shallower formations and to the surface can potentially impose significant risks to water quality and ecosystems [Frye et al, 2012;Hofmann et al, 2010].…”

Shallow groundwater system monitoring on controlled CO2 release sites: a review on field experimental methods and efforts for CO2 leakage detection

“…The behaviors of the injected CO 2 and its effects on the chemical changes of groundwater quality have been extensively proposed and discussed through laboratory (Little and Jackson, 2010;Lu et al, 2010;Frye et al, 2012;Terzi et al, 2014) and field tests (Kharaka et al, 2010;Cahill et al, 2014). It has been understood that gaseous CO 2 or CO 2 -infused groundwater has potential to degrade the shallowdepth groundwater quality (Bachu, 2008;Newmark et al, 2010;Harvey et al, 2012;Siirila et al, 2012).…”