Potential buffering capacity of naturally distributed carbonate minerals against future rises in atmospheric CO2 and coastal acidification: the Yellow Sea and three major estuaries in China.

The dissolution of marine carbonate minerals represents a scalable carbon dioxide (CO2) removal approach toward global climate goals. In this study, potential buffering capacity of naturally distributed carbonate minerals against future rises in atmospheric CO2 and thereby coastal acidification were assessed using field data obtained in the Bohai Sea, Yellow Sea and Chinese major estuaries. Results showed that highly soluble carbonate minerals such as calcite and aragonite dominated surface sediments, constituting 8-12 % of dry weight of sediments in Chinese major estuaries, while lowly soluble carbonate minerals (mostly dolomite) accounted for <1.5 %. At a conservative estimate, the South Yellow Sea particulate inorganic carbon (PIC) pool west of 124 °E in the region can potentially convert 21 × 109 mol CO2 (equivalent to 0.9 Mt CO2 or 0.25 Tg C) into bicarbonate. If the atmospheric CO2 further rises in the future, the Yellow Sea represents one of the most vulnerable systems within the Chinese seas to adverse impacts from ocean acidification. Based on the projection of CaCO3 saturation states under the future atmospheric CO2 rise, Yellow Sea aragonite pools will dissolve sooner than calcite pools. However, the future projection suggests that the air-equilibrated Ωcal will not decline to 2.0-2.1 in the Yellow Sea by the 2050s, implying that the South Yellow Sea's calcite pool may not play an important role in buffering the atmospheric CO2 rise.