High-Resolution Imaging Reveals How Raindrops Spread Bacteria Into The Air

Posted: Mar 7 2017, 10:30pm CST | by , Updated: Mar 7 2017, 10:31pm CST, in News | Latest Science News

 

High-Resolution Imaging Reveals How Raindrops Spread Bacteria into the Air
Credit: MIT
 

MIT researches observe the effect of rainfall on dry soil loaded with bacteria

Rain can contribute to spread bacteria far and wide.

When raindrops hit the ground, microbes living in the soil could be splashed into the air and carried through the wind. High resolution images show that raindrops can act as a dispersing agent, causing to send bacteria long distances. 

Researchers have long noted a link between the rainfall and the outbreaks of disease, but the underlying mechanism has remained unknown. To observe the effect of raindrops on soil filled with bacteria, researchers from the Massachusetts Institute of Technology used high-resolution cameras and provided a new insight into the process.

As the raindrops land on the dry soil, bubbles appear on the surface and release a spray of mist or aerosols. Each aerosol can carry up to several thousand bacteria from the soil and that bacteria can remain alive for more than an hour afterward. So, it turns out if the soil is contaminated with bacteria and it rains, aerosols could launch bacteria off the ground. And if there’s wind, bacteria could travel a good distance before settling back on the ground to colonize a new location.

“We’ve now found that rain could further disperse it. Manmade droplets from sprinkler systems could also lead to this type of dispersal. So this (study) has implications for how you might contain a pathogen.” Cullen Buie from MIT’s Department of Mechanical Engineering said in a statement.

In the lab, researchers looked at the rainfall effect on six types of dry soil, containing three species of bacteria. They simulated rainfall by releasing single drop of water from various heights and observed the aerosols bursting up from the surface. Researchers varied the surface temperature of the soil, as well as the height at which a droplet was released to see how different soils respond under different circumstances. 

The team found that droplets produced the highest number of aerosols in soils with temperatures of around 86 degrees Fahrenheit, which similar to soils found in tropical regions. Droplets also produced more aerosols when poured on sandy clay soil, falling at speeds between 1.4 and 1.7 meters per second - about the intensity of a light rain shower. Researchers were also able to predict the amount of aerosols released, depending on the type of soil, the density of bacteria within a given soil, the soil temperature and the speed of raindrop.

Now, that the researchers have identified the mechanism by which rains spew bacteria into the air, they can begin to develop ways to prevent the travelling of pathogens as well as predict the places and environmental conditions where rain is more likely to spread diseases. 

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Hira Bashir covers daily affairs around the world.

 

 

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