Editing Smog (section)

===Natural causes===
====Volcanoes====
An erupting volcano can emit high levels of [[sulfur dioxide]] along with a large quantity of particulate matter; two key components to the creation of smog. However, the smog created as a result of a volcanic eruption is often known as [[vog]] to distinguish it as a natural occurrence. The chemical reactions that form smog following a volcanic eruption are different than the reactions that form photochemical smog. The term smog encompasses the effect when a large number of gas-phase molecules and particulate matter are emitted to the atmosphere, creating a visible [[haze]]. The event causing a large number of emissions can vary but still result in the formation of smog.

====Plants====
Plants are a natural source of hydrocarbons that can undergo reactions in the atmosphere and produce smog. Globally both plants and soil contribute a substantial amount to the production of hydrocarbons, mainly by producing [[isoprene]] and [[terpene]]s.<ref>{{Cite book|url=https://www.elsevier.com/books/chemistry-of-the-natural-atmosphere/warneck/978-0-12-735632-7|title=Chemistry of the Natural Atmosphere, Volume 71 - 2nd Edition|last=Elsevier|website=www.elsevier.com|date=29 October 1999 |isbn=978-0-12-735632-7 |language=en|access-date=15 November 2018}}</ref> Hydrocarbons released by plants can often be more reactive than man-made hydrocarbons. For example when plants release isoprene, the isoprene reacts very quickly in the atmosphere with hydroxyl radicals. These reactions produce hydroperoxides which increase ozone formation.<ref>{{Cite journal|last1=Sharkey|first1=T. D.|last2=Wiberley|first2=A. E.|last3=Donohue|first3=A. R.|date=17 October 2007|title=Isoprene Emission from Plants: Why and How|journal=Annals of Botany|language=en|volume=101|issue=1|pages=5–18|doi=10.1093/aob/mcm240|pmid=17921528|pmc=2701830|issn=0305-7364}}</ref>