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 has been detected in the gas phase using neutralization-reionization mass spectrometry. Both cyclic and chain structures were found. A number of monoxides SO are known where n= 5-10, where the oxygen is bonded to one sulfur. They can be prepared by oxidising the homocycles with trifluoroperoxoacetic acid: The compounds are yellow or orange-coloured and thermally unstable near room temperature. One dioxide is well characterized: the deep orange SO (m.p. 60–62 °�C with decomposition), which arises using trifluoroperoxoacetic acid. Lower sulfur oxides The lower sulfur oxides are a group of inorganic compounds with the formula SO, where m < 2n. These