Háskóli ÍslandsUniversity of IcelandPogge von Strandmann, Philip A. E.Burton, Kevin W.Snæbjörnsdóttir, Sandra ÓskSigfússon, BergurAradóttir, Edda S.Gunnarsson, IngviAlfreðsson, Helgi A.Mesfin, Kiflom G.Oelkers, Eric H.Gíslason, Sigurður Reynir2020-03-032020-03-032019-04-30Pogge von Strandmann, P.A.E., Burton, K.W., Snæbjörnsdóttir, S.O. et al. Rapid CO2 mineralisation into calcite at the CarbFix storage site quantified using calcium isotopes. Nat Commun 10, 1983 (2019). https://doi.org/10.1038/s41467-019-10003-82041-1723https://hdl.handle.net/20.500.11815/1574Publisher's version (útgefin grein).The engineered removal of atmospheric CO 2 is now considered a key component of mitigating climate warming below 1.5 °C. Mineral carbonation is a potential negative emissions technique that, in the case of Iceland’s CarbFix experiment, precipitates dissolved CO 2 as carbonate minerals in basaltic groundwater settings. Here we use calcium (Ca) isotopes in both pre- and post-CO 2 injection waters to quantify the amount of carbonate precipitated, and hence CO 2 stored. Ca isotope ratios rapidly increase with the pH and calcite saturation state, indicating calcite precipitation. Calculations suggest that up to 93% of dissolved Ca is removed into calcite during certain phases of injection. In total, our results suggest that 165 ± 8.3 t CO 2 were precipitated into calcite, an overall carbon storage efficiency of 72 ± 5%. The success of this approach opens the potential for quantification of similar mineral carbonation efforts where drawdown rates cannot be estimated by other means.1983eninfo:eu-repo/semantics/openAccessCarbon cycleGeochemistryJarðefnafræðiKolefniinfo:eu-repo/semantics/articleNature Communications10.1038/s41467-019-10003-8