View source for Acid rain

    [[Category:Jason Edit]]
[[Category:Translated to French]]
[[fr:Pluie acide]]
[[Category:Translated to Spanish]]
[[es:Lluvia ácida]]
[[File:acid rain.png|450px|thumb|Figure 1. Acid rain formation.<Ref>Wikimedia Commons [Online], AVailable: https://upload.wikimedia.org/wikipedia/commons/b/b1/Origins_of_acid_rain.svg</ref>]]
<onlyinclude>'''Acid deposition''' is any type of [[precipitation]] - rain, snow, sleet, hail, or fog - that has a lower [[pH]] (and is therefore more [[acid]]ic) than normal. However, the term almost always used for all of these is '''acid rain'''. This higher acidity can cause problems in ecosystems and the [[environment]], and remains one of the major environmental concerns from [[fuel]] use despite attempts to address the issue since the 1970s.<Ref name=pp/> </onlyinclude>

Acid rain is produced when [[water]] in the air combines with [[NOx|nitrogen oxides]] and [[SOx|sulfur dioxide]], two types of [[pollutant]]s, and then falls down the surface of the Earth. These pollutants may also collect on the Earth's surface and the rain may combine with it upon arrival to the Earth, so the term "'''acid deposition'''" is often preferred over acid rain.<Ref name=pp>Pollution Probe. ''The Acid Rain Primer''. Visit www.pollutionprobe.org</ref>

===Acidity===
Normal rain has a pH of around 5.6 so it is slightly acidic. this is due to the combination of [[carbon dioxide]] with the water in the air to form carbonic acid <ref name="EPAS">USEPA (May 30, 2020). ''Acid Rain Students Site'' [Online]. Accessible: https://www3.epa.gov/acidrain/education/site_students/phscale.html</ref>. This acidity is naturally neutralized when precipitation comes in contact with [[base (chemistry)|alkaline]] minerals such as calcium, magnesium, and potassium in rocks on Earth's surface. This acid neutralization process is behind the [[chemical weathering]] of rocks and is responsible for releasing bicarbonates into the soil and water systems, which then act as buffers against stronger acidic inputs.<Ref name=pp/> Acid rain, however, has a pH of around 4.2. This means that acid rain is approximately '''25 times more acidic''' than normal rain due to the logarithmic nature of the pH scale.

[[File:pHacid.png|800px|thumb|center|Figure 2. Acid rain relative to other acidic and basic substances on the pH scale.<ref>Adapted from Energy: Its use and the Environment. See Reference 8</ref>]]

==Impacts==

Acid rain has many detrimental effects on vegetation, freshwater ecosystems, and natural and man-made structures. It can also cause respiratory diseases in humans, especially those that have preexisting conditions.<Ref>B. Everett, G. Boyle, S. Peake and J. Ramage, "Penalties: Assessing the Environmental and Health Impacts of Energy Use," in ''Energy Systems and Sustainability'', 2nd ed., Oxford, UK: Oxford, 2013, ch.13, pp.543</ref> When lakes and other bodies of water become too acidic, typically less than a pH of 6.0, plants and aquatic life begin to suffer.<Ref name=pp/> Fish reproduction ability falters, with death or deformity being widespread among younger fish. Amphibians and invertebrates suffer similarly, which means that acidic lakes have very little to no animal life.<ref name=wolf>R. Wolfson, "Air Pollution" in ''Energy, Environment, and Climate'', 2nd ed., New York, NY: W.W. Norton & Company, 2012, ch. 6, sec. 2, pp. 129-142</ref>

The most notable impacts have been measured in northeastern sections of North America and Western Europe, with the sources of acidification being traced primarily to [[coal-fired power plant]]s which emit large amounts of NOx and SO<sub>2</sub>.<ref name=big>J. Kraushaar and R. Ristinen, "Acid Rain," in ''Energy and Problems of a Technical Society'', 2nd ed., Hoboken, NJ: Wiley, 1993, ch.14, sec.6, pp.404-407</ref> The acidity of precipitation can be seen in Figure 3 in the United States, and due to a combination of [[wind]] flows from the US and the production of pollutants within Canada, Eastern Canada also suffers from acid rain<ref name="Can">Environment and Climate Change Canada (May 31, 2020). "Acid Rain FAQ" [Online]. Accessible: https://www.ec.gc.ca/air/default.asp?lang=En&n=7E5E9F00-1</ref>. Various regulations and restrictions of pollutants have been implemented as a means of addressing the issue, and these power plants must use [[air pollution control devices]] to meet them. 

[[File:acidphus.png|700px|center|thumb|Figure 3. The acidity of rain by region in the U.S., with the northeastern regions having highest acidity concentrations.<Ref>EPA. ''Acid Rain in New England'' [Online], Available: http://www.epa.gov/region1/eco/acidrain/intro.html</ref>]]

After acid rain falls to the Earth, the effects depend on the type of rock and soil it encounters. Limestone is able to neutralize the acid content of the rain, while granitic bedrocks consisting of granite, quartz, and gneiss are not able to do so as easily<ref name=Can/>. The bedrock in the northeastern regions of Figure 2 is dominated by these granitic rock-types and is overlain only by thin soil layers which means neutralization of acidic precipitation is slow or nonexistent.<Ref name=big/> Lakes at higher elevations in these regions tend to be more acidic, and are considered "dead" if they are not able to support life. 

The build up of acid snow on mountains is also a negative consequence, especially since a large amount of the acidic content may be released all at once during the spring in mountain runoff. This chemical shock is devastating to plant life downstream.<Ref name=big/> Many high mountain lakes have been known to lose their fish populations due to increased acidity from snowmelt runoff<ref name=Can/>. 

[[File:AcidMineDrainage.jpg|thumb|right|Figure 4. Yellow boy observed in a small creek in Centralia, PA. (Michael C. Rygel via Wikimedia Commons)<ref>Wikimedia Commons (June 1, 2020). [Online]. Accessible: https://commons.wikimedia.org/wiki/File:PA_AcidMineDrainage.jpg</ref>.]]
===Acid Rock Drainage===
If preipitation falls onto rocks that contain sulfur bearing minerals such as Pyrite or Galena, the combination of microorganism metabolism and oxidizing atmosphere can lead to [[runoff]] with pH levels below three which is over '''100 times more acidic''' than traditional precipitation<ref name="arock">Warren, L.A. (2011). "Acid Rock Drainage". In: Reitner J., Thiel V. (eds) Encyclopedia of Geobiology. Encyclopedia of Earth Sciences Series. Springer, Dordrecht. [Online]. Accessible: https://link.springer.com/referenceworkentry/10.1007%2F978-1-4020-9212-1_3</ref>. This type of acid runoff is commonly found at old abandoned mine sites where sulfur-bearing minerals were previously mined for industrial and economic use. As a result this type of acid deposition is sometimes called '''Acid Mine Drainage'''. When the pH of these runoff waters rises above three as runoff is slowly neutralized by carbonates in the environment, the previously dissolved Iron precipitates out as Iron-Oxide compounds. This gives the waters a characteristic yellow-orange colouration known as ''Yellow boy''.

==Prevention==
Following the realization of the impacts of acid rain, many programs to limit pollution have been put in place around the world since the 1980s<ref name="Ngeo">Nunez, Christina (June 1st, 2020). "Acid Rain, Explained" [Onine]. Accessible: https://www.nationalgeographic.com/environment/global-warming/acid-rain/</ref>. The emissions of [[SOx|SO<sub>2</sub>]] have decreased by 40% in the United States, with acid rain levels down about 65% in 2005. The same is true for [[NOx]].<Ref name=hin>R. A. Hinrichs and M. Kleinbach, "Acid Rain," in ''Energy: Its Use and the Environment'', 5th ed. Toronto, Ont. Canada: Brooks/Cole, 2006, ch.8, sec.C, pp.252-256</ref> This is made possible by the use of air pollution control devices, such as [[scrubber]]s and [[electrostatic precipitator]]s. Coal power plants and other industrial facilities require these devices in order to meet restrictions on emissions, and can reduce the emissions of some harmful pollutants by 99%<ref name=hin/>.

==For Further Reading==
*[[Acid]]
*[[Base]]
*[[The pH scale]]
*[[Chemical]]
*[[Water]]
*[[Water cycle]]
*Or explore a [[Special:Random|random page]]
==References==
{{Reflist}}
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