High-Resolution PM2.5 Metals in Pittsburgh: Trends, Fireworks, and Wildfire Impacts from the ASCENT Network

ZIHENG ZENG, Abhishek Anand, Theobard Habineza, Roya Bahreini, Ann M. Dillner, Armistead G. Russell, Nga Lee Ng, Coty Jen, Albert Presto, Carnegie Mellon University

     Abstract Number: 118
     Working Group: Burning Questions of Aerosol Emissions, Chemistry, and Impacts from Wildland-Urban Interface (WUI) Fires

Abstract
Metal species in particulate matter (PM2.5) are known contributors to harmful health effects and are often linked to combustion sources, both anthropogenic and natural. This study presents high-time-resolution data on metal concentrations in PM2.5 collected in Pittsburgh, PA using an Xact 625i ambient metals monitor over a 13-month period. The monitor is part of the Atmospheric Science & Chemistry mEasurement NeTwork (ASCENT) and is located at the Lawrenceville site—marking the first such metal dataset from this location. Hourly concentrations of over 40 elements were measured via X-ray fluorescence (XRF), capturing both long-term trends and short-lived emission events. We identify distinct seasonal variations, with potassium exhibiting significant summer peaks, likely influenced by regional biomass burning and fireworks activity. To identify episodic contributions, we conducted a focused analysis on two high-concentration events: the June 2023 Canadian wildfire smoke episode and local July 4th fireworks. During these events, we observed sharp increases in elements such as K, Ba, Cu, and Sr, with metal-to-potassium and metal-to-PM2.5 ratios offering diagnostic insights into source profiles. Background periods were used to define enrichment factors and contextualize these enhancements. Our results highlight the utility of continuous metal measurements for resolving short-term pollution episodes and improving source attribution. This work underscores the value of ASCENT’s real-time metal monitoring approach for characterizing dynamic urban air pollution and complements traditional filter-based measurements in understanding the evolving chemical composition of PM2.5