From TexAQS 2000 to ASCENT: The Evolution of Sources and Chemical Compositions of Nonrefractory Submicron Particles Based on Surface Aerosol Mass Spectrometry Measurements in Houston, Texas
FANGZHOU GUO, Robert Griffin, Manjula Canagaratna, Subin Yoon, Chun-Ying Chao, James Flynn, Barry Lefer, Shan Zhou, Luke Ziemba, Henry Wallace, Qili Dai, Benjamin Schulze, Roya Bahreini, Ann M. Dillner, Armistead G. Russell, Nga Lee Ng, Scott Herndon, Aerodyne Research, Inc.
Abstract Number: 485
Working Group: Coast to Coast Campaigns on Aerosols, Clouds, Chemistry, and Air Quality
Abstract
The Houston-Galveston-Brazoria (HGB) area historically has been subject to significant air pollution, with abundant emissions of highly reactive VOCs, NOX, and SO2 from local and regional sources including mobile sources, the petrochemical industry, and shipping emissions. The strong solar radiation, high ambient temperature and humidity, and seasonal inflow of airmasses from the Gulf of Mexico further complicate the conditions favorable for secondary aerosol and ozone formation, imposing a direct health threat to 2.3 million people.
Ever since their first deployment in the HGB area in Texas Air Quality Studies (TexAQS) in 2000, Aerodyne aerosol mass spectrometry instruments measured nonrefractory submicron particles through intermittent, intensive campaigns including TexAQS (2000), TexAQS-II (2006), DISCOVER-AQ (2013), HACHE and BEETEX (2014-2016), TRACER-MAP and TRACER-AQ2 (2022) and from continuous sampling at a suburban site since April 2024 as part of the ASCENT network.
Data from multiple quadrupole (Q-) and high-resolution time-of-flight (HR-ToF-) aerosol mass spectrometers (AMS) and aerosol chemical speciation monitors (ToF-ACSM) are reviewed (2000-2016), analyzed (2022-2024), and systematically evaluated with ancillary measurements to characterize the evolution of submicron aerosols in the HGB area over the past approximately 25 years. Preliminary findings indicate that the dominant contributors to NR-PM1 mass are organics (47%-64%) and sulfate (24-44%). Total NR-PM1 loadings (µg/m3) remain relatively stable across the urban core (12.8 (summer 2000), 11.0 (summer 2006), 9.7 (summer 2013), 10.8 (winter 2015), and 13.1 (summer 2022)). However, strong spatial variations are observed in peripheral urban-suburban mixed areas such as Conroe (11.6 (summer 2013)), Sugar Land (4.0 (summer 2014)), Galveston (4.7 (summer 2016)), and Liberty (9.1 (summer 2024)). Results from positive matrix factorization also reveal drastically changing sources of summer organic aerosol at the urban core, with POA/SOA ratio decreasing from 0.82 (summer 2000) and 0.75 (summer 2006) to 0.23 (summer 2013) and 0.12 (summer 2022).