AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Measurements of Nitrogen-Containing Organic Particle and Gas Phase Compounds with a New MOVI-HR-ToF-CIMS
CLAUDIA MOHR, Felipe Lopez-Hilfiker, Julia. D. Wargo, Nga Lee Ng, Lu Xu, Matthew Kollman, Peter Zotter, Andre Prévôt, Scott Herndon, Jonathan Franklin, Mark Zahniser, Leah Williams, Douglas Worsnop, Joel A. Thornton, University of Washington, Seattle, WA
Abstract Number: 503 Working Group: Aerosol Chemistry
Abstract Organic compounds are ubiquitous in the atmosphere and present in both gas and particle phase. Their evolution in time is determined by emissions, oxidation, deposition, and gas/particle partitioning especially for semi-volatiles (SVOCs). A fundamental understanding of this highly dynamic system requires quantitative measurements of organic compounds in both gas and particle phases.
Here we present data from an improved version of the Micro Orifice Volatilization Impactor High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (MOVI-HR-ToF-CIMS). While particles are impacted on a post for subsequent thermal desorption and analysis using chemical ionization mass spectrometry (CIMS), gases are drawn into the MOVI and analyzed in real time using CIMS, alternating ~every 15 min. Continuous switching between positive and negative ion proton transfer chemical ionization allows the detection of organic compounds with a variety of functional groups.
The instrument was recently deployed in a month-long field campaign (ClearfLo) in Detling, UK, from January 16 to February 15, 2012. The measurement site is influenced by local emissions from nearby roads and villages, continental air masses or the London plume. A high number of organic acids, as well as other compounds such as organonitrates and organosulfates, in both gas and particle phase up to an m/Q of ~500 Th could be detected and quantified. Nitrophenols, light-absorbing compounds in the UV, were detected at significant concentrations (a few nanograms per m3) in the particle phase. The consistency of their diurnal pattern with levoglucosan, syringic acid, and the absorbance of particulate matter at 370 nm measured with a 7-wavelength Aethalometer relates them mainly to biomass burning emissions and indicates their significance for the identification of “brown carbon” and its implications for the climate.
Initial statistical pattern analyses of the multi-dimensional field data set are also discussed.