Petrichor , the scent that occurs after light rainfall , is make by bacteria in the dirt that becomes airborne during the rainfall . While this has been know for decennary , there has n’t been an exact chemical mechanism bang . A unexampled study used a gamey - speed tv camera and found that spray can are generated when raindrop land on porous surface , and could excuse how petrichor occurs . realise this phenomenon could also help explain how E. coli and other pathogens are lifted from the soil where they can be ravish in the aura . The enquiry was conducted by Young Soo Joung and Cullen Buie from MIT , and their newspaper was published inNature Communications .
“ Until now , people did n’t know that aerosols could be generated from raindrops on soil , ” Joung said in apress release . “ This finding should be a good reference book for future work , sort out bug and chemicals existing inside soil and other natural material , and how they can be delivered in the environment , and maybe to humans . ”
Joung and Buie used the high - amphetamine camera to analyze one C of raindrop as they flow onto 16 kinds of dirt found in Massachusetts and 12 manufactured surface . They found that upon impact , the raindrop spreads out and traps bubbles of air . As the raindrop begins to retract from the fall , the bubble climb up up off the surface and get out as aerosol .
Sequence of raindrop hitting a holey surface and trapping the air bubbles , which then escape as aerosol droplets . Image good manners of Youngsoo Joung
Under idealistic conditions , hundreds of aerosol bomb droplets can shape in simple microsecond . The rate at which they are generate is subordinate upon the speed of the raindrop at impact , as well as the penning of the surface they impinge on . Heavy rain , which travel relatively promptly , impinge on many surfaces too quickly to yield the bubble .
When a light line current was applied during the study , the researchers noticed the droplets taking flight of steps . They suspect that this could be a contributing mechanism to the oil and bacteria that become airborne . Once those particles get in our nozzle and interact with our olfactory medulla oblongata , we are able to have the sweet-smelling smell of petrichor . While it has been known that bacterium is kick up by the rain , an exact chemical mechanism of how this happens has never before been investigated . This paper does not definitively land that aerosol shape in this fashion is that mechanism , but it does offer a plausible account .
“ Aerosols in the air for certain could be resulting from this phenomenon , ” Buie explained . “ perhaps it ’s not rain , but just a sprinkler system that could top to dispersal of contamination in the grunge , for perhaps a wider expanse than you ’d unremarkably await . ”
By extension , this could also be howsoil pathogens , such as E. coli and certain kingdom Fungi , are able-bodied to be inhaled and lead to infections . The researcher explored possible pathogen transmittance by adding fluorescent dye to the raindrops . They were able to confirm that the dyestuff was present in the droplets of aerosol , which point it may be possible for pathogen to be gestate in this way as well .
“ To prevent transmission of microorganisms from nature to humans , we need to know the precise chemical mechanism . In this work , we provide one possible way of infection , ” Joung conclude .
