Article

Aerosol generation by raindrop impact on soil

  • Nature Communications 6, Article number: 6083 (2015)
  • doi:10.1038/ncomms7083
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Abstract

Aerosols are investigated because of their significant impact on the environment and human health. To date, windblown dust and sea salt from sea spray through bursting bubbles have been considered the chief mechanisms of environmental aerosol dispersion. Here we investigate aerosol generation from droplets hitting wettable porous surfaces including various classifications of soil. We demonstrate that droplets can release aerosols when they influence porous surfaces, and these aerosols can deliver elements of the porous medium to the environment. Experiments on various porous media including soil and engineering materials reveal that knowledge of the surface properties and impact conditions can be used to predict when frenzied aerosol generation will occur. This study highlights new phenomena associated with droplets on porous media that could have implications for the investigation of aerosol generation in the environment.

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Acknowledgements

We are grateful to Dr Jim Bales and Ms Sandra J. Lipnoski of the MIT Edgerton Center for sharing their high-speed camera. We thank Zhifei Roy Ge for help with the aerosol experiments and David Hu for introducing us to the concept of ‘petrichor’. We also appreciate the reviewer comments, which bolstered the impact of this work. We thank Prof Gareth McKinley for discussions regarding the Washburn-Reynolds number.

Author information

Affiliations

  1. Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA

    • Young Soo Joung
    •  & Cullen R. Buie

Authors

  1. Search for Young Soo Joung in:

  2. Search for Cullen R. Buie in:

Contributions

Y.S.J. and C.R.B. designed the research; Y.S.J. performed the research; Y.S.J. and C.R.B. analysed the data and wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Young Soo Joung or Cullen R. Buie.

Supplementary information

PDF files

  1. 1.

    Supplementary Figures

    Supplementary Figures 1-2

Videos

  1. 1.

    Supplementary Movie 1

    Frenetic aerosol generation on porous media: the aluminium oxide thin layer chromatography plate (left) and the sandy clay soil (right). The Weber number (We ≡DoUo2γ-1) and the modified Peclet number (Pe ≡ (UoDo)/Dcap) are used to characterize the impact conditions of the droplets and the wetting properties of the surfaces, respectively. We ≡ 75 and Pe ≡ 174 for the porous aluminum surface. We ≡ 75 and Pe ≡ 320 for the sandy clay soil.

  2. 2.

    Supplementary Movie 2

    Aerosol generation on the clay loam soil with We ≡ 150 and Pe ≡ 1140.

  3. 3.

    Supplementary Movie 3

    The aerosol generation process when a single bubble breaks inside the droplet with We ≡ 8 and Pe ≡ 130. Aerosol dispersion when a single bubble, trapped in a droplet, bursts.

  4. 4.

    Supplementary Movie 4

    Frenetic water-jets and associated aerosols are generated on a thin layer chromatography plate after impact. We ≡ 75 and Pe ≡ 174.

  5. 5.

    Supplementary Movie 5

    Bubble formation inside water-droplets on a thin layer chromatography plate. We ≡ 11 and Pe ≡ 67.

  6. 6.

    Supplementary Movie 6

    Bubble formation inside water-droplets on a thin layer chromatography plate. The drop impact speed is 0.66 ms-1. We ≡ 19 and Pe ≡ 87.

  7. 7.

    Supplementary Movie 7

    Bubble formation inside water-droplets on a thin layer chromatography plate. The drop impact speed is 1.4 ms-1. We ≡ 75 and Pe ≡ 174.

  8. 8.

    Supplementary Movie 8

    Aerosol dispersion at the edge of droplets on a smooth porous surface. We ≡ 113 and Pe ≡ 501.

  9. 9.

    Supplementary Movie 9

    Convective migration of aerosol droplets generated on a porous media with air flows. We ≡ 75 and Pe ≡ 174.

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