Characterizing the Sources of Aerosols and Volatile Organic Compounds (VOCs) Impacting Air Quality at the Denver ASCENT Site

SEONSIK YUN, Douglas A. Day, Anne V. Handschy, Erick Mattson, Abby Koss, Maya Abou-Ghanem, Joost A. de Gouw, Rainer M. Volkamer, Roya Bahreini, Ann M. Dillner, Armistead G. Russell, Nga Lee Ng, Jose-Luis Jimenez, University of Colorado, Boulder

     Abstract Number: 389
     Working Group: Coast to Coast Campaigns on Aerosols, Clouds, Chemistry, and Air Quality

Abstract
Air pollution in the Denver metropolitan area has increased in recent years and is of concern due to its adverse effects on human health and regional visibility. Multiple sources likely contribute to this problem, including urban sources such as motor vehicles, industry, cooking, and volatile chemical products, regional sources such as agriculture, gas/oil extraction, biomass burning, and biogenic emissions, and continental background. Our understanding of the sources and their temporal variations in the Denver region remains insufficient, with information provided by field campaigns and routine air quality measurements of limited time resolution and chemical detail.

Since May 2023, we have deployed and operated several research-grade aerosol composition monitoring instruments in Denver as part of the new, long-term Atmospheric Science and Chemistry mEasurement NeTwork (ASCENT), supported by the US National Science Foundation. The ASCENT network comprises 12 monitoring sites across the United States, with the primary objective of characterizing aerosol chemical composition, physical properties, and boundary layer dynamics continuously with a high time resolution. In conjunction with the ASCENT instruments, we utilized a Vocus Proton Transfer Reaction Time-of-Flight Mass Spectrometer (Vocus PTR-TOF) to measure volatile organic compounds (VOCs) during several weeks in Summer 2023 and Winter 2024.

Here, we present an analysis of the sources and chemical composition of aerosols and VOCs in Denver, focusing on the first year of data from the ASCENT site. The results include temporal variations of aerosols and VOCs over multiple timescales and comparisons to past field campaigns to investigate long-term trends. Additionally, Positive Matrix Factorization analysis is conducted to further characterize the sources of urban air pollutants, background sources, and long-range transport. Finally, ongoing analysis will employ wind and trajectory analysis to evaluate the relative contributions of different emission sources in Denver and potential relationships with aerosol, VOC species, and other trace gases.