What chemical reactions in the soil cause that smell when it rains? In particular, what reactions in the soil causes the petrichor smell?


1 Answer 1


Interesting question. I actually had to look up the definition of petrichor. After getting a little nostalgic about rainfall, I decided to go ahead and forage around for an answer for you. I found a nice summary article here for those that are interested, and then a really nice bit of history here with a link to a great video about how rainfall helps to produce aerosols, which can contain the petrichor compounds.

Your question regards the reactions in the soil that give the petrichor smell, so let me get to that:

The main constituents of petrichor are volatile plant oils and geosmin. Oxidation of the fatty acids produced by plants can lead to some of the volatile compounds that constitute petrichor. Geosmin is a metabolite of actinobacteria and is produced through a biological pathway.

  1. https://en.wikipedia.org/wiki/Geosmin - a brief intro to Geosmin
  2. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3013058/ - A free paper highlighting the biosynthesis of geosmin
  • 3
    $\begingroup$ To all, be sure to see the high speed video of aerosols released from rain drops associated with the 2nd link. Pretty cool. $\endgroup$ Commented Jul 18, 2016 at 17:35
  • $\begingroup$ This answer should be accepted :) $\endgroup$ Commented May 10 at 3:51
  • $\begingroup$ Waking this up with a near query: I presume this is also generally the similar smell from a newly watered houseplant? $\endgroup$
    – civitas
    Commented Jun 3 at 0:07
  • $\begingroup$ unlikely I'd say. you'll smell petrichor strongest on warm concrete and rocks near trees and plants when it rains. give it a whiff and compare! $\endgroup$
    – Aaron
    Commented Jun 4 at 17:59

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