Assessment of mobile source contributions in El Paso by PMF receptor modeling coupled with wind direction analysis Eun Sug Park a, ⁎, David W. Sullivan b , Dong Hun Kang a , Qi Ying c , Clifford H. Spiegelman d a Texas A&M Transportation Institute, 3135 TAMU, College Station, TX 77843-3135, United States of America b The University of Texas at Austin, Center for Energy and Environmental Resources, 10100 Burnet Rd, Bldg 133, MC R7100, Austin, TX 78758-4445, United States of America c Zachry Department of Civil and Environmental Engineering, Texas A&M University, College Station, TX 77843-3136, United States of America d Department of Statistics, Texas A&M University, College Station, TX 77843-3143, United States of America HIGHLIGHTS • Vehicular contributions of ambient air emissions were assessed by PMF. • The analysis identified four major sources of hydrocarbon emissions in El Paso. • Vehicular contributions were deter- mined to be a significant contributor to hydrocarbons. • Contributions of mobile sources and LPG were highest when winds blow from the south. GRAPHICAL ABSTRACT abstract article info Article history: Received 17 October 2019 Received in revised form 19 February 2020 Accepted 22 February 2020 Available online 24 February 2020 Editor: Pavlos Kassomenos Keywords: Mobile source emissions Source apportionment Hydrocarbon Multivariate receptor modeling Positive matrix factorization It is well-known that El Paso is the only border area in Texas that has violated national air quality standards. Mo- bile source emissions (including vehicle exhaust) contribute significantly to air pollution, along with other sources including industrial, residential, and cross-border. This study aims at separating unobserved vehicle emissions from air-pollution mixtures indicated by ambient air quality data. The level of contributions from ve- hicle emissions to air pollution cannot be determined by simply comparing ambient air quality data with traffic levels because of the various other contributors to overall air pollution. To estimate contributions from vehicle emissions, researchers employed advanced multivariate receptor modeling called positive matrix factorization (PMF) to analyze hydrocarbon data consisting of hourly concentrations measured from the Chamizal air pollu- tion monitoring station in El Paso. The analysis of hydrocarbon data collected at the Chamizal site in 2008 showed that approximately 25% of measured Total Non-Methane Hydrocarbons (TNMHC) was apportioned to motor ve- hicle exhaust. Using wind direction analysis, researchers also showed that the motor vehicle exhaust contribu- tions to hydrocarbons were significantly higher when winds blow from the south (Mexico) than those when winds blow from other directions. The results from this research can be used to improve understanding source apportionment of pollutants measured in El Paso and can also potentially inform transportation planning strat- egies aimed at reducing emissions across the region. © 2020 Elsevier B.V. All rights reserved. 1. Introduction For the development of effective and efficient air emission control strategies, it is crucial to identify sources of major air pollutants and as- sess the impacts of the sources in the region of interest. Although mobile sources are substantial sources of criteria pollutants, such as Carbon Science of the Total Environment 720 (2020) 137527 ⁎ Corresponding author. E-mail address: e-park@tti.tamu.edu (E.S. Park). https://doi.org/10.1016/j.scitotenv.2020.137527 0048-9697/© 2020 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv