Atmospheric particles play a large role in the climate system by forming cloud droplets and absorbing or scattering solar radiation.  Organic species comprise a significant mass fraction of submicron atmospheric particles with considerable contribution from secondary organic aerosol, a significant fraction of which are formed from the oxidation of biogenic volatile organic compounds.  Aqueous-phase reactions in particles and cloud droplets are suggested to increase secondary organic aerosol mass and change the chemical composition of the atmospheric particles.  In this study, atmospheric particles and cloud water were collected onboard a research aircraft during the Southeast Oxidants and Aerosol Study (SOAS) over Alabama in June 2013.  We have utilized nanospray desorption electrospray ionization (nano-DESI) and direct electrospray ionization (ESI) coupled with high resolution mass spectrometry to probe the organic molecular composition of the particle and cloud water samples, respectively.  Our results indicate several hundred unique compounds identified in the atmospheric particles.  The fractions of CHO, CHNO, CHNOS, and CHOS-containing compounds in the particle and cloud water samples give insights into oxidation and aqueous processing pathways.  In particular, organosulfate compounds were ubiquitous in both the particle and cloud water samples; the formation of these compounds from organic nitrate and epoxide precursors will be discussed.  These data provide insights into the processing of organic compounds in cloud droplets and improve our understanding of atmospheric organic particle budgets and climate impacts.

Nitrogen- and sulfur-containing organic compounds in atmospheric particles and cloud water collected during SOAS

248th National Meeting (2014)

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