Dettori R, Donadio D. Carbon dioxide, bicarbonate and carbonate ions in aqueous solutions under deep Earth conditions.
Phys Chem Chem Phys 2020;
22:10717-10725. [PMID:
32103223 DOI:
10.1039/c9cp06904f]
[Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We investigate the effect of pressure, temperature and acidity on the composition of water-rich carbon-bearing fluids under thermodynamic conditions that correspond to the Earth's deep crust and upper mantle. Our first-principles molecular dynamics simulations provide mechanistic insight into the hydration shell of carbon dioxide, bicarbonate and carbonate ions, and into the pathways of the acid/base reactions that convert these carbon species into one another in aqueous solutions. At temperatures of 1000 K and higher, our simulations can sample the chemical equilibrium of these acid/base reactions, thus allowing us to estimate the chemical composition of diluted carbon dioxide and (bi)carbonate ions as a function of acidity and thermodynamic conditions. We find that, especially at the highest temperature, the acidity of the solution is essential to determine the stability domain of CO2vs. HCO3-vs. CO32-.
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