How+acid+rain+is+formed

= Normally   , the pH level of rain is about 5.6, which means it is a weak acid. Other chemicals can make this a stronger acid if they react with the rain. Acid rain is caused by the release of the gases sulfur dioxide and nitrous oxides into the atmosphere. The main sources of sulfur dioxide in South Africa are coal-fired power stations and metal working industries. The main sources of nitrous oxide emissions are vehicles and fuel combustion.  Sulfur dioxide reacts with water vapor and sunlight to form sulphuric acid. Likewise nitrous oxide forms nitric acid in the air. These reactions take hours, or even days, during which polluted air may move hundreds of kilometers. This means acid rain can fall far from the source of the pollution that caused it. When mist or fog droplets condense they will remove pollutants from the air and can become more stronger acid than acid rain. Even snow can be acidic. Gases and particles, not dissolved in water, with a low pH can also be deposited directly onto soil, grass and leaves. It is possible that even more acidity is deposited in this way than by rain. I  t can form from volcanoes, decaying vegetation and man made sources including sulfur dioxide and nitrogen oxides resulting from fossil fuel combustion. =
 * __How it is formed...__ ** 

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