acid rain

Definition

Rain which is unusually acidic (pH of less than the natural range of 5 to 6); caused mainly by atmospheric pollution with sulphur dioxide, carbon dioxide and nitrogen compounds.

Etymology

Coined in 1872 by Scottish chemist Robert Angus Smith.

Example Sentences

• "Acid rain forms when water in the atmosphere condenses on particles containing acid-forming pollutants, such as sulfate produced by the burning of fossil fuels and nitrogen oxides from automobile exhausts."