1a), trapped gas bubbles appear inside the droplet ( Fig. When a droplet hits the clay loam soil surface at a velocity consistent with light rainfall 31 ( Fig. The shape of a raindrop is not always spherical 27, 28, 29 because of the deformation in flight, but an assumed spherical shape is not unreasonable 30. 20, the diameter of a typical raindrop is 1–3 mm. When small water droplets, similar in size to raindrops, impinge on clay, sandy clay and clay loam 26, aerosol generation is observed. Using different impact velocities, we observed drop impingement on soils using a high-speed camera ( Fig. This work demonstrates that aerosols can be generated on porous surfaces including soil when impinged by a liquid droplet.Īerosol generation from droplets hitting soils We can predict when the frenetic aerosol generation occurs from the surface properties and impact conditions.
#Raindrop shape definition movie#
Within a specified range of impact velocities, we observe frenetic bubble generation and ejection of tiny droplets, producing aerosol above the surface ( Supplementary Movie 1). High-speed imaging provides visual proof of aerosol generation when liquid water droplets hit soil at velocities consistent with rainfall. In this work we provide evidence that rainfall on soil can also generate aerosols. Furthermore, this work could have widespread implications ranging from remediating the spread of disease-causing microbes to the earthy smell known as ‘petrichor’ present after a rain shower on a hot day 25. Because drop impingement-based aerosol generation can be employed using gravitational potential, it is promising for low-cost biological and environmental applications. There are several methods to generate aerosols such as electrospray, ultrasound and sprays however, most methods use external energy sources to generate aerosol droplets. However, to the best of our knowledge, aerosol generation from raindrops hitting soil has not been reported and the origins of atmospheric bioaerosols containing elements of soil and environmental microorganisms remain illusive 1, 8, 21.Īerosols generated from droplets hitting porous media can have significant impact on industrial applications as well as the environment 22, 23, 24. In addition, environmental aerosols are generated from both natural sources and anthropogenic activities such as volcanoes and combustion of fuels, respectively 3. Aerosol particles, larger than 1 μm, are known to originate from windblown dust and sea salt from sea spray resulting from bursting bubbles 6, 15, 16, 17, 18, 19, 20. Aerosols, which are tiny liquid droplets or solid particles suspended in a gas 1, 2, 3, have been investigated because of their significant impact on the environment, human health and industrial applications 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14.
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