Question

How do the pollutants that cause acid rain get into the air?

Answer 1

Pollutants that cause acid rain are typically released into the air as gases from industrial processes (factories usually).

Explanation:

The pollutants most commonly attributed to acid rain are sulfur dioxide (`SO_2`) and nitrogen dioxide (`NO_2`).

`SO_2` and `NO_2` are released from factories in gaseous form into the atmosphere, where they mix with water (`H_2O`) and hydroxides (`OH*`) which are normally present. When these chemicals mix they cause the neutral pH of atmospheric gases to become slightly acidic (the pH drops). The pH remains acidic as it falls as rain. Learn more about how acid rain forms here.

Infrastructure that is habitually exposed to acid rain will eventually deteriorate or discolor, plants aquatic life can be killed after just one storm. I'll write out the chemical equations below:

Sulfur Dioxide

`SO_2 + OH* -> HOSO_2*`

`HOSO_2` is an intermediary so it's immediate broken down through exposure to oxygen forming a hydroperoxyl (`HO_2*`) and sulfur trioxide (`SO_3`):

`HOSO_2* + O_2 -> HO_2* + SO_3`

`SO_3` is another intermediary and is immediately broken down into sulfuric acid (`H_2SO_4`) when `H_2O` is present:

`SO_3 (g) + H_2O (l) -> H_2SO_4 (aq)`

Nitrogen Dioxide

Nitrogen dioxide (`NO_2`) and a hydroxide ion (`OH*`) combine to form nitric acid (`HNO_3`):

`NO_2 + HO* -> HNO_3`

Read more about the formula of acid rain here.
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This is the Taj Mahal prior to an acid rain storm:

**Courtesy of: Rajesnewdelhi - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=29053600**

This is the Taj Mahal after an acid rain storm:

**Courtesy of: http://www.skymetweather.com/content/weather-faqs/what-is-acid-rain-and-its-adverse-effects/**

The Taj Mahal loacted in Agra, India is made of marble. That yellowing in the after picture is the result of the acid rain.