12 Apr 2023
 | 12 Apr 2023
Status: this preprint is open for discussion and under review for Atmospheric Measurement Techniques (AMT).

Acoustic levitation of pollen and visualisation of hygroscopic behaviour

Sophie A. Mills, Adam Milsom, Christian Pfrang, A. Rob MacKenzie, and Francis D. Pope

Abstract. Pollen are hygroscopic and so have the potential to act as cloud condensation nuclei (CCN) in the atmosphere. This could have yet uncertain implications for cloud processes and climate. Previous studies have investigated the hygroscopic swelling of pollen, linked to CCN activity by the κ-Köhler theory, using methods that follow observed mass increase by electrodynamic balance (EDB) or vapour sorption analyser. This study uses an acoustic levitator to levitate pollen grains in the true aerosol phase and uses a macroscope to image the pollen to investigate hygroscopic behaviour when relative humidity (RH) is changed. Two pollen species were studied in this work: Lilium orientalis (oriental lily) and Populus deltoides (eastern cottonwood). Both species were successfully levitated, however, the smaller Populus deltoides showed greater instability throughout experiments. The quality of images taken by the macroscope, and thus calculations of pollen area and diameter ratio, varied significantly and were sensitive to lighting conditions, as well as levitated pollen grain movement and orientation. Experiments with surface-fixed pollen grains were also conducted. They showed evidence that pollen hygroscopic swelling could be observed by the macroscope. The produced results were comparable with previously reported mass increase values. Although less accurate than methods that measure mass changes, the acoustic levitator and macroscope setup offer an attractive alternative by virtue of being commercial-off-the-shelf, low-cost, and versatile. A key advantage of this method is that it is possible to visually observe particle shape dynamics under varying environmental conditions.

Sophie A. Mills et al.

Status: open (until 27 Jun 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-670', Anonymous Referee #1, 23 Apr 2023 reply
  • RC2: 'Comment on egusphere-2023-670', Anonymous Referee #2, 02 Jun 2023 reply

Sophie A. Mills et al.

Sophie A. Mills et al.


Total article views: 323 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
246 67 10 323 20 2 3
  • HTML: 246
  • PDF: 67
  • XML: 10
  • Total: 323
  • Supplement: 20
  • BibTeX: 2
  • EndNote: 3
Views and downloads (calculated since 12 Apr 2023)
Cumulative views and downloads (calculated since 12 Apr 2023)

Viewed (geographical distribution)

Total article views: 328 (including HTML, PDF, and XML) Thereof 328 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 07 Jun 2023
Short summary
Pollen are important components of the atmosphere, which have the potential to impact upon cloud processes, through their ability to help in the formation of rain droplets. This study investigates the hygroscopicity of two different pollen species using an acoustic levitator. Pollen grains are levitated and their response to changes in relative humidity are investigated. A key advantage of this method is that it is possible study pollen shape under the varying environmental conditions.