Ever notice an earthy smell in the air after a light rain? Now scientists at MIT believe they may have identified the mechanism that releases this aroma, as well as other aerosols, into the environment.
Using high-speed cameras, the researchers observed that when a raindrop hits a porous surface, it traps tiny air bubbles at the point of contact. As in a glass of champagne, the bubbles then shoot upward, ultimately bursting from the drop in a fizz of aerosols.
The team was also able to predict the amount of aerosols released, based on the velocity of the raindrop and the permeability of the contact surface.
Ever notice an earthy smell in the air after a light rain? Now scientists at MIT believe they may have identified the mechanism that releases this aroma, as well as other aerosols, into the environment.
Using high-speed cameras, the researchers observed that when a raindrop hits a porous surface, it traps tiny air bubbles at the point of contact. As in a glass of champagne, the bubbles then shoot upward, ultimately bursting from the drop in a fizz of aerosols.
The team was also able to predict the amount of aerosols released, based on the velocity of the raindrop and the permeability of the contact surface.
The researchers suspect that in natural environments, aerosols may carry aromatic elements, along with bacteria and viruses stored in soil. These aerosols may be released during light or moderate rainfall, and then spread via gusts of wind.
“Rain happens every day — it’s raining now, somewhere in the world,” says Cullen R. Buie, an assistant professor of mechanical engineering at MIT. “It’s a very common phenomenon, and it was intriguing to us that no one had observed this mechanism before.”
Youngsoo Joung, a postdoc in Buie’s lab, adds that now that the group has identified a mechanism for raindrop-induced aerosol generation, the results may help to explain how certain soil-based diseases spread.
“Until now, people didn’t know that aerosols could be generated from raindrops on soil,” Joung says. “This finding should be a good reference for future work, illuminating microbes and chemicals existing inside soil and other natural materials, and how they can be delivered in the environment, and possibly to humans.”
Image shows that aerosol generation after drop impingement on porous media is a three-step process, consisting of bubble formation, bubble growth, and bubble bursting. Image courtesy of Youngsoo Joung via MIT News,
Read more at MIT News.
