<P> Acidic deposits have been detected in glacial ice thousands of years old in remote parts of the globe . </P> <P> Soils of coniferous forests are naturally very acidic due to the shedding of needles, and the results of this phenomenon should not be confused with acid rain . </P> <P> The principal cause of acid rain is sulphur and nitrogen compounds from human sources, such as electricity generation, factories, and motor vehicles . Electrical power generation using coal is among the greatest contributors to gaseous pollutions that are responsible for acidic rain . The gases can be carried hundreds of kilometers in the atmosphere before they are converted to acids and deposited . In the past, factories had short funnels to let out smoke but this caused many problems locally; thus, factories now have taller smoke funnels . However, dispersal from these taller stacks causes pollutants to be carried farther, causing widespread ecological damage . </P> <P> Combustion of fuels produces sulphur dioxide and nitric oxides . They are converted into sulphuric acid and nitric acid . </P>

The primary cause of acid rain around the world is
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