Rainy season is one of the most beautiful gifts given by the god. Everyone likes this season including plants and animals. This season mostly helps farmers. In the rainy season, when the rain hits the grounds, we get a peculiar smell and everyone likes that smell. I too like this smell. But I don’t know why this smell comes. Therefore I started researching what about by asking my elder brother and my teachers. I finally got the answer. It is because of bacteria and plants.
The smell we get rain touches the ground is called Petrichor.
The smell is similar to the smell of the Earth. Before the rain reaches the ground there is no smell in the air. When raindrops land on porous surfaces, the air from the pores form air bubbles which float on the surface of the rainwater and release aerosols. These aerosols produce the smell.
The smell we get from rain is more, when the rainfall is not heavy. Heavy rain falls cannot produce this distinct smell as the rainwater mixes with dirt and other foreign particles. Therefore petrichor occurs only when the rainfall is light.
The distinct smell of the petrichor is formed by two agents who are
1. Bacteria
2. Plants
Bacteria
Soil-dwelling bacteria known as actinomycetes produce spores in dry soil. When the rain falls on these spores, they get displaced and carried away by the moist air. Therefore we can smell them when it rains.
Plants
Certain plants and trees release oils that get collected on soil and rocks are exposed to rainfall. This causes these oils from plants and trees to mix with the air causing the petrichor.
The ozone layer is also another reason for this distinct smell.
Conclusion
The plants secrete certain oils during dry periods and when it rains, those oils are mixed with air. Bacteria release certain spores which are forced to release during rainfall. Therefore the distinct smell of the air just after the rainfall is because of these reasons. Finally, we can understand the phenomenon.