Radiocarbon analysis as a method for verifying atmospheric CO2 uptake during carbon mineralization

Sequestration of atmospheric CO2 is required to constrain the warming of Earth’s climate. Carbon mineralization refers to the precipitation of carbonate minerals by reaction of CO2 and Mg- and Ca-rich rocks; if the source of the CO2 is atmospheric and the precipitated carbonate is protected from subsequent dissolution, this process at sufficient scale may be able to reliably draw down atmospheric greenhouse gas levels. Such reactions occur passively in ultramafic settings and previous work has demonstrated that they actively draw down local CO2(g) concentrations. However, a method for unambiguously attributing the sequestered carbon solid product to atmospheric sources is still lacking. Here, we test if radiocarbon can be used to verify that the carbon being incorporated into carbonate minerals during carbon mineralization is atmospheric in origin. Samples from recently exposed ultramafic sites are analyzed and the results demonstrate the utility of this technique for verifying true atmospheric carbon reduction.