Atmospheric Chemistry Program Seminar: Andrew Jensen, CU-ANYL Chem

Measurements of Volatile Organic Compounds in Urban Air by Proton-Transfer Reaction Mass Spectrometry
Andrew Jensen,
de Gouw Group
CU ANYL Dissertation Defense
"Volatile organic compounds (VOCs) in urban environments are emitted to the atmosphere from many biogenic and anthropogenic sources. VOC oxidation contributes to the formation of secondary products, including ozone and secondary organic aerosol, which negatively impact air quality and human health. As emissions change, VOC measurements are necessary to reassess their role in urban air quality. Here, I present results from measurements of ambient VOCs in three urban environments made by proton-transfer reaction mass spectrometry (PTR-MS) with part-per-trillion by volume detection limits.
I first detail the quantification of VOCs measured in Boulder, CO in spring 2021 with a focus on instrument characterization. I developed a PTR Data Tool to parameterize instrument response which, in turn, informs the quality of the measurements and the quantification of VOCs which cannot be directly calibrated. These findings help streamline and improve future PTR-MS measurements.
VOCs were also measured in Changzhou, an industrial Chinese city, before, during, after the 2020 COVID-19 lockdowns which shut down non-essential activities. I quantified strong reductions in industrial and transportation emissions. These estimates help inform emission inventories and chemistry-transport models during this global perturbation of air pollution, as well as possible future scenarios with reduced emissions.
Finally, VOCs were measured in the Los Angeles basin, California during summer 2022. Ambient concentrations of primary VOCs from vehicles have declined over the preceding decade due to emission regulations while concentrations of secondary VOCs were largely unchanged, in part, due to faster oxidation and unregulated emission sources. This study expands the detected subset of urban VOCs and allows for a more detailed understanding of atmospheric sources and fates."