Editing Acid rain (section)

===Natural phenomena===
{{Bar chart|title=Mean acidifying emissions (air pollution) of different foods per 100g of protein<ref name="Nemecek 987–992">{{cite journal |last1=Poore |first1=J. |last2=Nemecek |first2=T. |title=Reducing food's environmental impacts through producers and consumers |journal=Science |date=June 2018 |volume=360 |issue=6392 |pages=987–992 |doi=10.1126/science.aaq0216 |pmid=29853680 |bibcode=2018Sci...360..987P |doi-access=free }}</ref>|float=right|label_type=Food Types|data_type=Acidifying Emissions (g SO<sub>2</sub>eq per 100g protein)|bar_width=20|width_units=em|data_max=344|label1=[[Beef]]|data1=343.6|label2=[[Cheese]]|data2=165.5|label3=[[Pork]]|data3=142.7|label4=[[Lamb and mutton|Lamb and Mutton]]|data4=139.0|label5=[[Aquaculture|Farmed Crustaceans]]|data5=133.1|label6=[[Poultry]]|data6=102.4|label7=[[Aquaculture|Farmed Fish]]|data7=65.9|label8=[[Egg as food|Eggs]]|data8=53.7|label9=[[Faboideae|Groundnuts]]|data9=22.6|label10=[[Peas]]|data10=8.5|label11=[[Tofu]]|data11=6.7|label12=|data12=|label13=|data13=}}The principal natural [[phenomena]] that contribute acid-producing gases to the [[Earth's atmosphere|atmosphere]] are emissions from volcanoes.<ref>{{cite journal |last1=Floor |first1=G.H. |last2=Calabrese |first2=S. |last3=Román-Ross |first3=G. |last4=D´Alessandro |first4=W. |last5=Aiuppa |first5=A. |title=Selenium mobilization in soils due to volcanic derived acid rain: An example from Mt Etna volcano, Sicily |journal=Chemical Geology |date=October 2011 |volume=289 |issue=3–4 |pages=235–244 |doi=10.1016/j.chemgeo.2011.08.004 |bibcode=2011ChGeo.289..235F |hdl=10447/66526 |s2cid=140741081 |hdl-access=free }}</ref> Thus, for example, [[fumarole]]s from the Laguna Caliente crater of [[Poás Volcano]] create extremely high amounts of acid rain and fog, with acidity as high as a pH of 2, clearing an area of any vegetation and frequently causing irritation to the eyes and lungs of inhabitants in nearby settlements. Acid-producing gasses are also created by [[biology|biological]] processes that occur on the land, in [[wetland]]s, and in the [[ocean]]s. The major biological source of sulfur compounds is [[dimethyl sulfide]].

Nitric acid in [[rain]]water is an important source of fixed [[nitrogen]] for plant life, and is also produced by electrical activity in the atmosphere such as [[lightning]].<ref>{{cite web|url=https://www.livescience.com/63065-acid-rain.html|title=Acid Rain: Causes, Effects and Solutions|website=[[Live Science]]|date=July 14, 2018|access-date=August 23, 2019|archive-date=August 23, 2019|archive-url=https://web.archive.org/web/20190823203539/https://www.livescience.com/63065-acid-rain.html|url-status=live}}</ref>

Acidic deposits have been detected in [[glacier|glacial ice]] thousands of years old in remote parts of the globe.<ref name="Likens, G. E. 1979"/>