Why does exposure to atmospheric pollution change basic lead II carbonate into lead II sulphate?

Polluted air contains oxides of sulfur, which dissolve in water to form stronger (more ionized) acids than the carbonic acid from which carbonates are derived. Therefore, the sulfuric and/or sulfurous acids formed by water and polluted air displace the carbonates as carbon dioxide, according to the ionic equation (for sulfuric acid):

CO3-2 + H2SO4 -> SO4-2 + H2O + CO2.