A51J-3159:
Insights into Aqueous-phase processing through Comparison of the Organic Chemical Composition of Atmospheric Particles and Cloud Water in the Southeast United States
Friday, 19 December 2014
Eric Boone1, Julia Laskin2, Alexander Laskin2, Christopher Wirth3, Paul B Shepson4, Brian H Stirm4 and Kerri Pratt5, (1)University of Michigan, Ann Arbor, MI, United States, (2)Pacific Northwest National Laboratory, Richland, WA, United States, (3)Purdue University, Department of Chemistry, West Lafayette, IN, United States, (4)Purdue Univ, West Lafayette, IN, United States, (5)University of Michigan Ann Arbor, Department of Chemistry and Department of Earth & Environmental Sciences, Ann Arbor, MI, United States
Abstract:
Organic compounds comprise a significant mass fraction of submicron atmospheric particles with considerable contribution from secondary organic aerosol (SOA), a large fraction of which is formed from the oxidation of biogenic volatile organic compounds. Aqueous-phase reactions in particles and cloud droplets are suggested to increase SOA mass and change the chemical composition the particles following cloud evaporation. Aqueous-phase processing may also explain discrepancies between measurements and models. To gain a better understanding of these processes, cloud water and below-cloud atmospheric particles were collected onboard a research aircraft during the Southeast Oxidants and Aerosol Study (SOAS) over Alabama in June 2013. Nanospray desorption electrospray ionization (nano-DESI) and direct electrospray ionization (ESI) coupled with high resolution mass spectrometry were utilized to compare the organic molecular composition of the particle and cloud water samples, respectively. Several hundred unique compounds have been identified in the particle and cloud water samples, allowing possible aqueous-phase reactions to be examined. Hydrolysis of organosulfate compounds, aqueous-phase formation of nitrogen-containing compounds, and possible fragmentation of oligomeric compounds will be discussed, with comparisons to previous laboratory studies. This study provides insights into aqueous-phase reactions in ambient cloud droplets.
