Status: this preprint is currently under review for the journal ACP.
Ammonium-adduct chemical ionization to investigate anthropogenic oxygenated gas-phase organic compounds in urban air
Peeyush Khare1,a,Jordan E. Krechmer2,Jo Ellen Machesky1,Tori Hass-Mitchell1,Cong Cao3,Junqi Wang1,Francesca Majluf2,b,Felipe Lopez-Hilfiker4,Sonja Malek1,Will Wang1,Karl Seltzer5,Havala O. T. Pye6,Roisin Commane7,Brian C. McDonald8,Ricardo Toledo-Crow9,John E. Mak3,and Drew R. Gentner1,10Peeyush Khare et al.Peeyush Khare1,a,Jordan E. Krechmer2,Jo Ellen Machesky1,Tori Hass-Mitchell1,Cong Cao3,Junqi Wang1,Francesca Majluf2,b,Felipe Lopez-Hilfiker4,Sonja Malek1,Will Wang1,Karl Seltzer5,Havala O. T. Pye6,Roisin Commane7,Brian C. McDonald8,Ricardo Toledo-Crow9,John E. Mak3,and Drew R. Gentner1,10
Received: 11 Jun 2022 – Discussion started: 14 Jun 2022
Abstract. 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 VCPs in a U.S. megacity over a 10-day 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 (NH4+) 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/functionalized compounds with ratios to common anthropogenic marker compounds and compares their relative abundances to two regionally-resolved emissions inventories used in urban air quality models.
Urban ambient measurements via ammonium-adduct (NH4+) time-of-flight mass spectrometry explore the diverse mix of compounds emitted from volatile chemical products that include volatile to semi-volatile organic compounds across various chemical classes (e.g. glycols, glycol ethers, acetates, acrylates) with concentrations ranging from parts per trillion to parts per billion levels. The results are used to evaluate state-of-the-art regionally-resolved emission inventories.
Urban ambient measurements via ammonium-adduct (NH4+) time-of-flight mass spectrometry explore...