Volatility-Resolved Measurements of Total Gas-Phase Organic Compounds by High Resolution Electron Impact Mass Spectrometry

Aerosol particles have important impacts on visibility, acid deposition, climate, and human health, although large uncertainties remain in quantifying their chemical composition and atmospheric transformations. A large fraction of the anthropogenic aerosol is generated from energy-related activities, and organic compounds are known to constitute a significant fraction of ambient aerosol mass. Recently discovered discrepancies between measurements of organic aerosol mass and predictions from large scale atmospheric models suggest that our understanding of the sources of secondary organic aerosol is incomplete. This SBIR project addresses the critical need for improved chemical characterization of the gas-phase organic compounds that serve as precursors for organic aerosol in the atmosphere. We will develop and test a novel instrument for the measurement and characterization of atmospheric Total Gas-Phase Organics. Gas-phase organic compounds will be collected cryogenically, desorbed, and measured with high-resolution electron impact mass spectrometry, a general technique allowing for the measurement of the total mass of all organic species, as well as key chemical characteristics, such as the oxygen-to-carbon ratio. Temperature control of the sample desorption process will give information on the volatility of the organic compounds, a crucial element in understanding gas to particle conversion. The Phase I project successfully demonstrated the feasibility of the Total Gas-Phase Organics instrument. A prototype was constructed and characterized in the laboratory. The prototype was deployed in a field campaign for intercomparison with other measurements of gas-phase organics. During Phase II, a commercial version of the instrument will be developed. Specific tasks include optimizing the design of the inlet and detector, developing techniques for separating gas- and condensed-phase organics, and developing new data analysis tools for analyzing the complex chemically and volatility resolved datasets that will be acquired. Commercial Applications and Other Benefits: The TGO instrument will be available as a stand-alone instrument or as a module for use with all existing and future aerosol mass spectrometer systems. The primary market for this instrument will be atmospheric research groups at universities and national laboratories. In addition, the instrument will be well-suited for environmental monitoring, as well as for the characterization of emissions from a variety of industrial and energy production processes, including aircraft combustors, gas turbines, fluidized bed combustors, diesel combustors, and conventional furnaces. We expect that the system developed in this program will yield a significant level of direct commercial sales and contract field measurements from the atmospheric science and environmental pollution research and development communities.