Acid rain

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Acid rain can make the leaves fall off trees. It damages statues.
Gargoyle that has been damaged by acid rain

Acid rain is rain that is unusually acidic. It is rain with high levels of hydrogen ions (low pH). It may be defined as "rain water having pH less than 5.6".

Acid rain can have harmful effects on plants, animals and humans. It is caused when gaseous compounds of ammonium, carbon, nitrogen, and sulphur are released into the atmosphere. The wind carries the gases high into the sky. There the compounds react with the water in the atmosphere and acids are made. In 1852, Robert Angus Smith showed the relationship between acid rain and atmospheric pollution in Manchester.[1] He coined the term "acid rain" in 1872.[2]

Causes[change | change source]

Acid rain is caused by acids mixing with air. The largest source of acid is sulfur dioxide. Carbon dioxide and various oxides of nitrogen also make acid in the atmosphere. These chemicals are both natural and artificial.

There are various natural causes, such as gases from volcanoes. However, it is thought that air pollution by people now causes most acid rain. People started producing more acidic gases when they started building factories and power stations. These buildings as well as houses and vehicles burn coal or oil that have sulfur in them. This releases gases into the air that produce acid rain.[3] Governments have tried since the 1970s to reduce the amount of sulfur being released into the Earth's atmosphere, and have had good results so far. However, it is expensive to clean the smoke from factories and power stations. In 2001 Great Britain still produced about five million tonnes of these gases every year; and China produced 18 million tonnes. The United States produced more than 20 million tonnes then,[3] which declined to 8.1 million in 2010.

Trees are destroyed by acid rain. Fish are also killed by acid rain.

Acid rain can also be caused naturally. For example, acids can be made by nitrogen compounds made by lightning, and volcanic eruptions can release sulfur dioxide into the atmosphere.

Effects[change | change source]

Acid rain has been shown to have a bad impact on forests, freshwater and soil. It kills insect and aquatic life-forms as well as causes damage to buildings and having impacts on human health.

Acid rain poisons rivers and lakes. Fish and other animals cannot live in acid water.[3] It is also bad for buildings as the acid damages calcium carbonate stone. The acid dissolves it. Many buildings and monuments have been damaged by acid rain.[3]

References[change | change source]

  1. Seinfeld, John H.; Pandis & Spyros N 1998. Atmospheric chemistry and physics — from air pollution to climate change. John Wiley. ISBN 978-0-471-17816-3
  2. Acid rain in New England: a brief history. Retrieved on 2013-02-09.
  3. 3.0 3.1 3.2 3.3 Border, Rosemary (2001). Pollution. Oxford University Press. ISBN 0 19 422868 1.