scholarly journals Carbon dioxide, bicarbonate and carbonate ions in aqueous solutions under deep Earth conditions

2020 ◽  
Vol 22 (19) ◽  
pp. 10717-10725
Author(s):  
Riccardo Dettori ◽  
Davide Donadio
Keyword(s):  
Carbon Dioxide ◽  
Aqueous Solutions ◽  
Upper Mantle ◽  
Crust And Upper Mantle ◽  
Effect Of Pressure ◽  
Deep Crust ◽  
Carbonate Ions ◽  
Deep Earth ◽  
Thermodynamic Conditions

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.

scholarly journals The fate of carbon dioxide in water-rich fluids under extreme conditions

2016 ◽  
Vol 2 (10) ◽  
pp. e1601278 ◽  
Author(s):  
Ding Pan ◽  
Giulia Galli
Keyword(s):  
Carbon Dioxide ◽  
Upper Mantle ◽  
Carbonic Acid ◽  
Global Climate ◽  
Extreme Conditions ◽  
Dissolved Carbon ◽  
Dissolved Carbon Dioxide ◽  
Deep Earth ◽  
Geochemical Models ◽  
Dynamics Simulations

Investigating the fate of dissolved carbon dioxide under extreme conditions is critical to understanding the deep carbon cycle in Earth, a process that ultimately influences global climate change. We used first-principles molecular dynamics simulations to study carbonates and carbon dioxide dissolved in water at pressures (P) and temperatures (T) approximating the conditions of Earth’s upper mantle. Contrary to popular geochemical models assuming that molecular CO2(aq) is the major carbon species present in water under deep Earth conditions, we found that at 11 GPa and 1000 K, carbon exists almost entirely in the forms of solvated carbonate (CO32−) and bicarbonate (HCO3−) ions and that even carbonic acid [H2CO3(aq)] is more abundant than CO2(aq). Furthermore, our simulations revealed that ion pairing between Na+ and CO32−/HCO3− is greatly affected by P-T conditions, decreasing with increasing pressure at 800 to 1000 K. Our results suggest that in Earth’s upper mantle, water-rich geofluids transport a majority of carbon in the form of rapidly interconverting CO32− and HCO3− ions, not solvated CO2(aq) molecules.

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