Acid Rain - Definition, Causes, Effects of Acid Rain What is Acid Rain? Acid rain, as the name suggests, can be said as the precipitation of acid in the form of rain in the simplest way. When atmospheric pollutants like nitrogen and sulphur oxides react with rainwater and fall with the rain, this results in acid rain. (Credits: Google Images) Definition of Acid Rain Acid rain is made up of highly acidic water droplets due to emissions into the air, more specifically disproportionate levels of sulphur and nitrogen emitted by vehicles and manufacturing processes. It is often called acid rain as this concept contains many types of acid precipitation. Acid deposition takes place in two ways: wet and dry. Wet deposition is any form of precipitation that removes acids from the atmosphere and places them on the earth's surface. In the absence of precipitation, the dry deposition of polluting particles and gases adheres to the ground through dust and smoke. Causes of Acid Ra...