AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Improved Discrimination Between Dust and Bioaerosol by Aerosol Time-of-Flight Mass Spectrometry
GAVIN CORNWELL, Camille Sultana, Markus Petters, Hashim Al-Mashat, Nicholas Rothfuss, Hans Taylor, Paul DeMott, Sonia Kreidenweis, Andrew Martin, Kimberly Prather, University of California, San Diego
Abstract Number: 489 Working Group: Bioaerosols
Abstract Ice nucleating particles (INPs) are rare atmospheric particles that can greatly affect clouds and precipitation through their ability to trigger cloud glaciation at warmer temperatures than would occur in their absence. Two particle sources that have been shown to be particularly efficient at initiating ice formation in clouds are dust and bioaerosols. Dust has modest ice nucleation (IN) activity at temperatures below -15 ºC and is emitted and transported at high altitudes globally in significant quantities. Bioaerosols are less abundant, but certain species possess exceptional IN-activity and may be especially important due to their ability to trigger ice formation at temperatures as warm as ‑1ºC. Single particle mass spectrometry is a sophisticated but technically challenging method for in-situ measurements of INP composition. Of particular concern is that dust and bioparticles have overlapping mass spectral features, complicating their unambiguous detection. In this work, we present a detailed analysis of standards for dust and bioaerosol. Using insights informed by this analysis, we developed a decision tree for the identification of cellular bioaerosol at a site in coastal California using an aerosol time-of-flight mass spectrometer. These particles showed moderate correlations with a subset of fluorescent particles measured by the wideband integrated bioaerosol sensor and displayed temporal profiles that tracked INP concentrations measured at T = -15 ºC, suggesting that this particle type could serve as a useful proxy for INPs active at modest supercooling.