When calcium carbonate (a solid typically found in rocks such as limestone) reacts with acidic free hydrogen (H⁺) ions in seawater, the solid calcium carbonate dissolves, forming free calcium (Ca²⁺) ions and free bicarbonate (HCO₃^–) ions . The free hydrogen ions are consumed resulting in decreased hydrogen ion activity. In other words calcium carbonate acts to neutralise or buffer the solution by consuming hydrogen ions [8].

Similarly calcium and magnesium bicarbonates, which are present in seawater at a concentration of approximately 140 mg/l [11] consume free hydrogen ions, decreasing hydrogen ion activity, i.e. the bicarbonates in the seawater used for scrubbing act to neutralise or buffer the solution by consuming hydrogen ions.