Approach for Measuring the Chemistry of Individual Particles in the Size Range Critical for Cloud Formation

Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California 92093, United States.
Analytical Chemistry (Impact Factor: 5.64). 02/2011; 83(6):2271-8. DOI: 10.1021/ac103152g
Source: PubMed


Aerosol particles, especially those ranging from 50 to 200 nm, strongly impact climate by serving as nuclei upon which water condenses and cloud droplets form. However, the small number of analytical methods capable of measuring the composition of particles in this size range, particularly at the individual particle level, has limited our knowledge of cloud condensation nuclei (CCN) composition and hence our understanding of aerosols effect on climate. To obtain more insight into particles in this size range, we developed a method which couples a growth tube (GT) to an ultrafine aerosol time-of-flight mass spectrometer (UF-ATOFMS), a combination that allows in situ measurements of the composition of individual particles as small as 38 nm. The growth tube uses water to grow particles to larger sizes so they can be optically detected by the UF-ATOFMS, extending the size range to below 100 nm with no discernible changes in particle composition. To gain further insight into the temporal variability of aerosol chemistry and sources, the GT-UF-ATOFMS was used for online continuous measurements over a period of 3 days.

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    • "Zauscher et al. (2011) developed a water-based growth tube system which uses condensation to grow particles which would be too small for optical detection. This enables the detection and analysis of particles down to 38 nm (Zauscher et al., 2011). The rapid single particle mass spectrometer (RSMS) has also been applied to single particle studies (Phares et al., 2003; Lake et al., 2003; Tolocka et al., 2004) with some success. "
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    • "Characterisation of the chemical composition of particles smaller than 50 nm is hindered by difficulties in transmission of ultra-small particles through aerodynamic lenses and the limitations of the optical detection methods. To alleviate these problems, Zauscher et al. [59] coupled a growth tube to an ultrafine ATOFMS. Small particles (40–60 nm) grow to larger sizes in the growth tube in the presence of water vapour, which enables their detection using the standard optical detection scheme. "
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