Springtime showers have brought more than just rain to our region. They have also brought with them the delightful scent of petrichor, a term coined by Australian scientists in 1964 to describe the smell produced by rain. Petrichor is not a substance in itself, but rather a combination of chemical compounds released by or contained within the rain that interact to create the recognizable scent we associate with rain.
The scent of petrichor is created by several different compounds, including ozone and geosmin. Ozone is typically found in the atmosphere and can be absorbed by rain as it falls through the air. Lightning during a rain event can also produce more ozone as it impacts oxygen molecules in the atmosphere. Geosmin, a chemical produced by bacteria in the soil called Actinomycetes, is also released into the air by falling raindrops and can be detected by the human nose at very low concentrations.
Plants also play a role in creating the complex chemical stew that is petrichor. During dry conditions, plants produce compounds that accumulate in the soil until rain falls. When the rain fills the voids in the soil, it pushes out these compounds, including stearic and palmitic acid. The scent of petrichor is further enhanced as the rain clears
