Humanity and the Weather

Water Pollution

What is the difference between normal rain pH and acid rain pH?

The normal pH of rain water is 5.0 to 5.6, while acid rain has a pH of about 4.3 (compared to distilled water, with a neutral pH of 7.0). Natural rain water is slightly acidic because of dissolved carbon dioxide, which actually makes it similar to club soda without the bubbles. Under some conditions, such as after dust storms, rain can become more alkaline, and volcanoes can add sulfur to clouds and contribute to acid rain. One extreme example of the latter happened in 1783, when Iceland’s Laki volcano erupted and spewed so much sulfur into the air that acid rain killed the island’s crops and polluted the air over Europe.


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