Schematic of <a href="https://en.wikipedia.org/wiki/volcano" class="extiw" title="en:volcano">en:volcano</a> injection of <a href="https://en.wikipedia.org/wiki/Particulate" class="extiw" title="en:Particulate">aerosols</a> and gases.  Source: <a rel="nofollow" class="external free" href="https://pubs.usgs.gov/of/of97-262/of97-262.html">http://pubs.usgs.gov/of/of97-262/of97-262.html</a> (figure modified from Richard Turco in American Geophysical Union Special Report: Volcanism and Climate Change, May 1992)
Acid rain also occurs from air pollution.