Acid rain

External audio
External audio
	"Whatever Happened to Acid Rain?", Science History Institute

Acid rain is rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but acid rain has a pH level lower than this and ranges from 4–5 on average.^[1]^[2] The more acidic the acid rain is, the lower its pH is.^[2] Acid rain can have harmful effects on plants, aquatic animals, and infrastructure. Acid rain is caused by emissions of sulfur dioxide and nitrogen oxide, which react with the water molecules in the atmosphere to produce acids.

Acid rain has been shown to have adverse impacts on forests, freshwaters, soils, microbes, insects and aquatic life-forms.^[3] In ecosystems, persistent acid rain reduces tree bark durability, leaving flora more susceptible to environmental stressors such as drought, heat/cold and pest infestation. Acid rain is also capable of detrimenting soil composition by stripping it of nutrients such as calcium and magnesium which play a role in plant growth and maintaining healthy soil. In terms of human infrastructure, acid rain also causes paint to peel, corrosion of steel structures such as bridges, and weathering of stone buildings and statues as well as having impacts on human health.^[4]^[5]^[6]^[7]

Some governments, including those in Europe and North America, have made efforts since the 1970s to reduce the release of sulfur dioxide and nitrogen oxide into the atmosphere through air pollution regulations. These efforts have had positive results due to the widespread research on acid rain starting in the 1960s and the publicized information on its harmful effects.^[8]^[9] The main source of sulfur and nitrogen compounds that result in acid rain are anthropogenic, but nitrogen oxides can also be produced naturally by lightning strikes and sulfur dioxide is produced by volcanic eruptions.^[10]

^ "Drinking Water Regulations and Contaminants". US EPA. September 3, 2015. Retrieved October 19, 2021.
^ ^a ^b Cite error: The named reference :1 was invoked but never defined (see the help page).
^ US EPA, OAR (March 16, 2016). "Effects of Acid Rain". epa.gov. Retrieved March 29, 2022.
^ Magaino, S. (January 1997). "Corrosion rate of copper rotating-disk-electrode in simulated acid rain". Electrochimica Acta. 42 (3): 377–382. doi:10.1016/S0013-4686(96)00225-3.
^ Cite error: The named reference EPA: Forests was invoked but never defined (see the help page).
^ Cite error: The named reference :8 was invoked but never defined (see the help page).
^ Effects of Acid Rain – Human Health Archived January 18, 2008, at the Wayback Machine. Epa.gov (June 2, 2006). Retrieved on 2013-02-09.
^ P. Rafferty, John. "What Happened to Acid Rain?". Encyclopædia Britannica. Retrieved July 21, 2022.
^ Kjellstrom, Tord; Lodh, Madhumita; McMichael, Tony; Ranmuthugala, Geetha; Shrestha, Rupendra; Kingsland, Sally (2006), Jamison, Dean T.; Breman, Joel G.; Measham, Anthony R.; Alleyne, George (eds.), "Air and Water Pollution: Burden and Strategies for Control", Disease Control Priorities in Developing Countries (2nd ed.), World Bank, ISBN 978-0-8213-6179-5, PMID 21250344, archived from the original on August 7, 2020, retrieved April 22, 2020
^ Sisterson, D. L.; Liaw, Y. P. (1990). "An evaluation of lightning and corona discharge on thunderstorm air and precipitation chemistry". Journal of Atmospheric Chemistry. 10 (1): 83–96. Bibcode:1990JAtC...10...83S. doi:10.1007/BF01980039. S2CID 97714446.

[:5-1] "Drinking Water Regulations and Contaminants". US EPA. September 3, 2015. Retrieved October 19, 2021.

[:1-2] Cite error: The named reference :1 was invoked but never defined (see the help page).

[:10-3] US EPA, OAR (March 16, 2016). "Effects of Acid Rain". epa.gov. Retrieved March 29, 2022.

[:11-4] Magaino, S. (January 1997). "Corrosion rate of copper rotating-disk-electrode in simulated acid rain". Electrochimica Acta. 42 (3): 377–382. doi:10.1016/S0013-4686(96)00225-3.

[EPA:_Forests-5] Cite error: The named reference EPA: Forests was invoked but never defined (see the help page).

[:8-6] Cite error: The named reference :8 was invoked but never defined (see the help page).

[:9-7] Effects of Acid Rain – Human Health Archived January 18, 2008, at the Wayback Machine. Epa.gov (June 2, 2006). Retrieved on 2013-02-09.

[:13-8] P. Rafferty, John. "What Happened to Acid Rain?". Encyclopædia Britannica. Retrieved July 21, 2022.

[:6-9] Kjellstrom, Tord; Lodh, Madhumita; McMichael, Tony; Ranmuthugala, Geetha; Shrestha, Rupendra; Kingsland, Sally (2006), Jamison, Dean T.; Breman, Joel G.; Measham, Anthony R.; Alleyne, George (eds.), "Air and Water Pollution: Burden and Strategies for Control", Disease Control Priorities in Developing Countries (2nd ed.), World Bank, ISBN 978-0-8213-6179-5, PMID 21250344, archived from the original on August 7, 2020, retrieved April 22, 2020

[:14-10] Sisterson, D. L.; Liaw, Y. P. (1990). "An evaluation of lightning and corona discharge on thunderstorm air and precipitation chemistry". Journal of Atmospheric Chemistry. 10 (1): 83–96. Bibcode:1990JAtC...10...83S. doi:10.1007/BF01980039. S2CID 97714446.

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