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Online Measurement of Semi-volatile Tracer Molecules in Workplace Room Air using Thermal Desorption Aerosol Gas Chromatography-Mass Spectrometry
WEN XU, Philip Croteau, Nathan Kreisberg, Allen Goldstein, John Jayne, Douglas Worsnop, Aerodyne Research, Inc.
Abstract Number: 370
Working Group: Instrumentation and Methods
Abstract
Knowing the chemical composition of aerosols is key to understanding their sources and to making effective control policies to reduce air pollution. Scientists often use offline filter-based techniques to capture detailed chemical compositions of aerosols. However, these techniques are usually labor-intensive and are not applicable when high time-resolution is a priority for accurate source appointment, especially in regions where the meteorology could change in hours.
In the current work, we demonstrate the application of online thermal desorption aerosol gas chromatography (TAG) mass spectrometry for measuring semi-volatile tracer molecules in room air of a workplace environment with a time resolution of about 1 hour. Time series of two organic compounds, levoglucosan and triethanolamine, were measured. The temporal profile of levoglucosan agrees well with the biomass burning organic aerosol (BBOA) factor measured using a collocated aerosol chemical speciation monitor (ACSM). The diurnal profile of levoglucosan shows elevated concentration during nighttime in winter, considered to be due to increased domestic wood-burning activity in local area homes and provides insight into the air exchange rates of the building HVAC system. The temporal profile of triethanolamine shows a strong weekday and weekend pattern. Its concentration is elevated when activities are going on in the machine shop inside the building, suggesting a possible source from metal cutting fluid. Filter blanking measurements show that both levoglucosan and triethanolamine are mainly in the particle phase. In summary, the TAG-MS system shows great potential in providing hourly molecular- resolved data for source apportionment, complementing both offline filter-based techniques and high time-resolution, but low molecular resolution, instruments, such as aerosol mass spectrometers.