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Detailed Comparisons of Organic Aerosol Composition Measurements Using Advanced Mass Spectrometric Techniques
ERIK HELSTROM, Abigail Koss, Jordan Krechmer, Manjula Canagaratna, Frank Keutsch, Alexander Zaytsev, Jesse Kroll, MIT
Abstract Number: 494
Working Group: Instrumentation and Methods
Abstract
While the mass yield of secondary organic aerosol (SOA) from a number of volatile organic carbon precursors under different oxidation conditions has been measured for some time, the chemical composition of these condensed-phase products remains a source of substantial uncertainty. An incomplete understanding of the composition of SOA precludes the formulation of general formation mechanisms or a causal understanding of its overall physical and chemical properties. Therefore, it is necessary to develop instrumentation capable of measuring the full chemical range of carbon-containing species present. In recent decades, great strides have been made in detecting and quantifying additional organic species, owing to advancements in inlet design and the proliferation of ionization schemes for mass spectrometry. However, to our knowledge there is still uncertainty as to the observational intersections of these techniques – which species are measured by multiple instruments, and which species may remain unmeasured. A number of chamber oxidation experiments were performed to test the coverage of chemical identities detected in real time by a suite of these new instruments. Here we present an intercomparison of the measurements -- Filter Inlet for Gases and Aerosols-Iodide-Chemical Ionization Mass Spectrometer (FIGAERO-I-CIMS), Thermal Denuder-Proton Transfer Reaction-Mass Spectrometer (TD-PTR-MS), Thermal Denuder-Ammonium-Chemical Ionization Mass Spectrometer (TD-NH4-CIMS), and Aerosol Mass Spectrometer (AMS) -- of condensed-phase organic species collected during these experiments, identifying the remaining gaps and measurement overlaps this observing system provides. We use reduced-parameter frameworks which provide a solid foundation for assessing overall coverage in chemical space. Beyond this, we examine the evolution of individual species/ion signals over time to demonstrate consistencies and outstanding deficiencies across measurements. Ultimately this work aims to assist the development of systematic metrics by which future instrument deployments can be assessed.