Carbonate Dissolution

Definition

Calcium carbonate is a chemical compound with the formula CaCO₃. It is the main component of shells of marine organisms. Calcium carbonate can dissolve in seawater to form calcium and hydrogen carbonate ions.

$$ {\mathrm{Ca}\mathrm{CO}}_3+{\mathrm{CO}}_2+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{Ca}}^{2+}+2{\mathrm{H}\mathrm{CO}}_3^{-} $$

Several crystal structures of calcium carbonate are found in the marine environment. The most common crystal structures in the ocean are calcite and aragonite, but also ikaite occurs in cold-water environments.

The crystal structure determines how easy these crystals can dissolve, a property that is expressed as the solubility product, K_sp,

$$ {\mathrm{K}}_{\mathrm{sp}}=\left[{\mathrm{Ca}}^{2+}\right]\times \left[{\mathrm{HCO}}_3^{2-}\right] $$

where [Ca²⁺] and $\left[{\mathrm{HCO}}_3^{2-}\right]$ equal the concentration of these properties in the surrounding media. The value of K_spis dependent on temperature, salinity, and pressure. The...