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Coalescence Sampling and Analysis of Aerosols using Aerosol Optical Tweezers

We present a first exploratory study to assess the use of aerosol optical tweezers as an instrument for sampling and detecting accumulation and coarse mode aerosol. A sub-picolitre aqueous aerosol droplet is captured in the optical trap and used as a sampling volume, accreting mass from a free flowing aerosol generated by a medical nebuliser or atomiser. Real-time measurements of the initial stability in size, refractive index and composition of the sampling droplet inferred from Raman spectroscopy confirm that these quantities can be measured with high accuracy and low noise. Typical standard deviations in size and refractive index of the sampling droplet over a period of 200 s are <±2 nm and <±0.0005, respectively, equivalent to <±0.04 % in both measured quantities. A standard deviation of <±1 % over a 200 s period is achieved in the spontaneous Raman intensity measurement. When sampling coarse mode aerosol, mass changes of <10 pg can be detected by the sampling droplet as discrete coalescence events. With accumulation mode aerosol, we show that fluxes as low as 0.068 pg s-1 can be detected over a 50 s period, equivalent to ~3 pg of sampled material.

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Creator(s) Rose Willoughby, Andrew Orr-Ewing, Jonathan Reid, Bryan Bzdek
Publication date 25 Jan 2017
Language eng
Publisher University of Bristol
Licence Non-Commercial Government Licence for public sector information
DOI 10.5523/bris.1ttc1y9kic0311l7c5n2oq45oe
Citation Rose Willoughby, Andrew Orr-Ewing, Jonathan Reid, Bryan Bzdek (2017): Coalescence Sampling and Analysis of Aerosols using Aerosol Optical Tweezers. https://doi.org/10.5523/bris.1ttc1y9kic0311l7c5n2oq45oe
Total size 2.5 MiB

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