Sulphur dioxide (SO2) is a colourless gas with a pungent odour, released into the atmosphere from both natural sources, such as volcanic eruptions, and anthropogenic (human-caused) sources emitted by the combustion of fuels containing sulphur.
Sulphur dioxide is a pollutant that contributes to acid deposition, which, in turn, can lead to potential changes in soil and water quality (eutrophication due to excessive nutrient input, as discussed above). Its effects can be counterbalanced by implementing flue gas desulfurization systems in power plants, and regulations on emissions from transportation sources. Winter smog and acidification are among the results of its presence in our atmosphere.