AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Molecular Characterization of Cloud Water Using Ultrahigh-Resolution FT-ICR Mass Spectrometry
YUNZHU ZHAO, Parichehr Saranjampour, Anna Gannet Hallar, Lynn Mazzoleni, Michigan Technological University
Abstract Number: 379 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Clouds act as a medium for interactions between gaseous and particulate phase substances altering the composition of atmospheric organic matter (AOM). To investigate this further, samples of supercooled clouds were collected at Storm Peak Laboratory in Colorado (3220 m asl). Approximately, 5000 molecular formulas were assigned to AOM isolated using a reverse phase extraction procedure and analyzed by electrospray ionization ultrahigh-resolution FT-ICR mass spectrometry (100 < m/z < 700). The components have a wide range of double bond equivalents (DBE = number of rings and double bonds), ranging from 0 to 19, an average oxygen-to-carbon ratio (O/C) of 0.58 ± 0.09, and an average hydrogen-to-carbon ratio (H/C) of 1.5 ± 0.24. The values indicate that the compounds range from aliphatic to aromatic, however a majority of them are aliphatic. The compounds assigned with only carbon, hydrogen and oxygen from cloud water AOM were compared to assigned formulas from other studies [1-3]. The comparison of aerosol water soluble organic carbon (WSOC) indicated 34-66% of the WSOC components were in common with the cloud water AOM. However, a large number of unique compounds in cloud water AOM were also observed. The unique compounds have aliphatic and highly oxidized elemental ratios (H/C ≥1.5 and O/C ≥ 1). The comparison of cloud water AOM and rainwater AOM [4] showed higher similarity with respect to the ranges of the observed elemental ratios but differ substantially with respect to the number of assigned molecular formulas. Compounds with high O/C ratios were observed in both cloud water and rainwater samples, but were not observed in the aerosol samples, indicating the importance of aqueous phase reactions in forming more highly oxidized AOM compounds.
References:
[1]Mazzoleni et al., EnvChem, InPress, 2012.
[2]Schmitt-Kopplin et al., AnalChem, Vol. 82, 2010.
[3]Wozniak et al., AtmosChemPhys, Vol. 8, 2008.
[4]Altieri et al., AtmosChemPhys, Vol. 9, 2009.