Metal release from limestones at high partial-pressures of CO2

Interactions of arsenic with calcite surfaces revealed by in situ nanoscale imaging

“…Depending on the pH of the leaching fluid, up to 0.35 ppm of arsenic, mostly As (V) , was concentrated in the leachate. In other limestones extracted from several well cores in Oklahoma, USA, up to 3.6 ppm of arsenic is present in calcite (Wunsch et al, 2014), raising the possibility of contamination of groundwater by CO 2 injection into geological repositories and subsequent calcite dissolution. Batch experiments of leaching of such rocks by CO 2 -rich fluids showed that a concentration of arsenic of 30 ppb can be reached in 40 days, a high concentration controlled both by the dissolution of calcite and by desorption from other minerals (Wunsch et al, 2014).…”

Effect of a controlled sub-seabed release of CO 2 on the biogeochemistry of shallow marine sediments, their pore waters, and the overlying water column

“…Processes controlling metal release into pore waters at elevated CO 2 concentrations include mineral dissolution and desorption of cations from mineral surfaces (Ardelan and Steinnes, 2010;Kirsch et al, 2014;Wunsch et al, 2014Wunsch et al, , 2013. During the QICS experiment, concentrations of a number of metals, including Ca, Fe and Mn, and the metalloid Si, increased in the Table 6 Concentrations of metals in sediments collected from Zone 1 on D13/D14, D42/D43 and D53/D54.…”

“…Bednarsek et al, 2012;Fabricius et al, 2011;Krause et al, 2012;Murray et al, 2013;Riebesell et al, 2007). In addition, rates of some natural mineral weathering reactions increase at low pH (Ganor et al, 1995), and dissolution and/or desorption of metals from minerals may be enhanced (Payán et al, 2012;Wunsch et al, 2014Wunsch et al, , 2013. These mobilised metals may accumulate in marine organisms (López et al, 2010), can inhibit growth or even have lethal effects (Riba et al, 2003;Basallote et al, 2014).…”

On the mobilization of metals by CO2 leakage into shallow aquifers: exploring release mechanisms by modeling field and laboratory experiments

“…conducted a series of sequential leaching tests with sediments from a shallow groundwater formation in Mississippi, USA. Constituents that were mobilized were As, Ba, Ca, Fe, Ge, Mg, Mn, Na, Ni, Si, Sr, Zn, which are largely consistent with the Type I cations reported by Lu et al Wunsch et al . reacted rock samples from three limestone aquifers with 0.01–1 bar CO 2 for up to 40 days, and found increasing concentrations of Ca, Mg, Sr, Ba, Tl, U, Co, As and Ni from the dissolution of mostly calcite and to a lesser extent pyrite.…”

“…Together, these experiments analyzed various types of sediments (e.g. essentially carbonate‐free in Varadharajan et al vs. carbonate‐dominated in Wunsch et al …”