How does marble’s calcitic composition react to acidic rainwater?
Marble, primarily composed of calcite (calcium carbonate, CaCO₃), reacts chemically with acidic rainwater, which contains dissolved carbon dioxide (CO₂) forming weak carbonic acid (H₂CO₃). This acid reacts with calcite, dissolving it and producing calcium ions (Ca²⁺), bicarbonate (HCO₃⁻), and water. Over time, this reaction leads to surface erosion, loss of detail, and structural weakening in marble structures. The process is accelerated in areas with high pollution, as sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) create stronger acids like sulfuric and nitric acid, further speeding up dissolution. This weathering phenomenon is a key concern in preserving historical marble monuments and buildings.
