Studying airborne atmospheric aerosol in an ultrasonic trap.


The aim of the presented research is to improve the understanding of the impact of chemical ageing of atmospheric aerosol on cloud formation, radiative forcing and, ultimately, climate change.  To achieve this goal, an acoustic levitator is being developed and applied to three classes of aerosol which are important to atmospheric sciences:  aqueous droplets, ice and mineral dust particles.  Model systems representative of atmospheric processes are being investigated, their physical and chemical modifications in varying conditions are being monitored specifically to obtain insight into the behaviour of atmospheric particles.  The potential of acoustic levitation as a tool for atmospheric sciences will be explored.


Acoustic levitation is a cost-effective, compact and mobile technique that allows container-less reaction monitoring.  This technique is currently under-exploited for atmospheric sciences.  Robust, reliable and simultaneous levitation of several liquid and solid particles has been achieved for a wide range of diameters, shapes and materials.  Key features for application of the acoustic levitation approach to atmospheric sciences include:

  1. Ultrasonic streaming for creation of condensed organic monolayers on aqueous droplets;
  2. Drop distortion for direct and contact-less measurement of the surface tension of droplets; and
  3. An acoustic ‘cold trap’ for investigation of individual ice particles at low temperatures.

These proof-of-principle experiments will improve our understanding of several important aerosol processes occurring in the atmosphere and provide valuable new input for aerosol and cloud models.

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