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Expanded observations of oxygenated organic compounds in urban emissions via ammonium-adduct chemical ionization mass spectrometry
Citation:
Khare, P., J. Krechmer, T. Hass-Mitchell, J. Wang, J. Machesky, F. Majluf, H. Stark, F. Lopez-Hilfiker, K. Seltzer, H. Pye, C. Cao, R. Commane, R. Toledo-Crow, J. Mak, AND D. Gentner. Expanded observations of oxygenated organic compounds in urban emissions via ammonium-adduct chemical ionization mass spectrometry. IGAC Conference, virtual, Virtual, September 12 - 17, 2021.
Impact/Purpose:
This work reports 150 species measured in ambient air in New York City air and compares them to EPA's Volatile Chemical Product (VCPy) inventory. VCPy methods will be used in the 2020 National Emissions Inventory (NEI).
Description:
Emissions from volatile chemical products and other non-traditional sources have become increasingly important for urban air quality and bottom-up calculations estimate emissions for a variety of functionalized compounds that remain understudied and uncertain in emissions inventories. We employ a Vocus high-resolution time-of-flight mass spectrometer with ammonium (NH4+) as the reagent ion to minimize analyte fragmentation and extend the range of observable oxygenates without the relative humidity-dependence of other NH4+ implementations. Using this instrument, we present new online measurements of a wide range of oxygenated compounds at an elevated site in New York City. Observations include volatile, intermediate-volatility, and semivolatile oxygenates and other organic compounds, which were collected at the rooftop observatory of the Advanced Science Research Center (City University of New York) in upper Manhattan, over a 10-day period during Winter 2020 (pre-COVID) when biogenic sources and photochemistry were less active. These observations are supplemented by offline gas chromatography with high-resolution mass spectrometry and online measurements of carbon monoxide (CO). Among a diverse range of observed ions, atmospheric abundances of over 150 chemical formulas were measured by Vocus NH4+-CIMS, whose likely assignments spanned a wide range of functionalized compound classes including glycols, glycol ethers, alcohols, acetates, ethanolamines, fatty acid methyl esters, and others that originate from various consumer, commercial, and industrial products, including personal care products and widely-used solvents. Their concentrations were dynamic and varied with wind direction, including enhancements over the highly-populated areas of Manhattan and the surrounding region that reached parts per billion (ppb) levels for some compounds. These top-down measurements are used to generate emissions ratios against common anthropogenic tracers (e.g. CO, benzene) and compared to emissions inventories specifically for New York City generated using the new VCPy framework that will be used in constructing the next U.S. National Emissions Inventory (NEI).
