Weathering release occurs of Ca and other ions into surface waters. Rainfall is acidic because atmospheric carbon dioxide dissolves in the rainwater producing weak carbonic acid. In unpolluted environments, the rainfall pH is around 5.6. Acid rain occurs when gases such as sulfur dioxide and nitrogen oxides are present in the atmosphere. These oxides react in the rain water to produce stronger acids and can lower the pH to 4.5 or even 3.0. Sulfur dioxide, SO, comes from volcanic eruptions or from fossil fuels, can become sulfuric acid within rainwater, which can cause solution weathering to the rocks on which it
Lower sulfur oxides Disulfur monoxide (SO) is an unstable analogue of sulfur dioxide. Like SO as well as ozone (O), and trisulfur (S), it adopts a bent structure. The S-S bond length is 188.4pm, the S-O bond is 146.5pm and the SSO angle is 117.88. The two dipole moment components are μa = 0.875D and μb = 1.18D This species decomposes to give a polymeric sulfur oxides ("PSO's") with the approximate formula [SO]. PSO's decompose at room temperature to elemental sulfur and SO. PSO's have been proposed to be responsible for the colour of Io. Trisulfur monoxide, SO is an unstable molecule. It