Citation:

Khare, P., J. Krechmer, J. Machesky, T. Hass-Mitchell, C. Cao, J. Wang, F. Majluf, F. Lopez-Hilfiker, S. Malek, W. Wang, K. Seltzer, H. Pye, R. Commane, B. McDonald, R. Toledo-Crow, J. Mak, AND D. Gentner. Ammonium adduct chemical ionization to investigate anthropogenic oxygenated gas-phase organic compounds in urban air. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, Germany, 22(21):14377–14399, (2022). https://doi.org/10.5194/acp-22-14377-2022

Impact/Purpose:

In 2021, EPA ORD scientists in this output developed VCPy as a tool to estimate gas-phase emissions from volatile chemical products (VCPs). VCPy has been adopted by EPA/OAQPS to estimate emissions from the VCP sector in the 2020 NEI. In this work, VCPy emission estimates are compared to observations of oxygenated volatile organic compounds measured in ambient New York City. The ambient sampling, led by external collaborators, occurred during a time when when photochemistry was lower than other times of year and species were more directly related to emissions. This work finds VCPy is overall consistent with measurements, but discrepancies exist for some species and could be driven by differences in spatial scale, product composition, or other factors.

Description:

Volatile chemical products (VCPs) and other non-combustion-related sources have become important for urban air quality, and bottom-up calculations report emissions of a variety of functionalized compounds that remain understudied and uncertain in emissions estimates. Using a new instrumental configuration, we present online measurements of oxygenated organic compounds in a US megacity over a 10 d wintertime sampling period, when biogenic sources and photochemistry were less active. Measurements were conducted at a rooftop observatory in upper Manhattan, New York City, USA using a Vocus chemical ionization time-of-flight mass spectrometer, with ammonium (NH as the reagent ion operating at 1 Hz. The range of observations spanned volatile, intermediate-volatility, and semi-volatile organic compounds, with targeted analyses of ∼150 ions, whose likely assignments included a range of functionalized compound classes such as glycols, glycol ethers, acetates, acids, alcohols, acrylates, esters, ethanolamines, and ketones that are found in various consumer, commercial, and industrial products. Their concentrations varied as a function of wind direction, with enhancements over the highly populated areas of the Bronx, Manhattan, and parts of New Jersey, and included abundant concentrations of acetates, acrylates, ethylene glycol, and other commonly used oxygenated compounds. The results provide top-down constraints on wintertime emissions of these oxygenated and functionalized compounds, with ratios to common anthropogenic marker compounds and comparisons of their relative abundances to two regionally resolved emissions inventories used in urban air quality models.

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