Realistic VOC Emissions and SOA Potential of Asphalt Pavement

HUAWEI LI, Kyah Gracia, Yanyu Zhang, Daniel Gonzalez, John Williams, Hovanness Dingilian, Thomas Eckel, David R. Cocker III, University of California, Riverside

     Abstract Number: 130
     Working Group: Urban Aerosols

Abstract
Asphalt surfaces have been proposed as significant urban sources of volatile organic compounds (VOCs) and intermediate-volatility organic compounds (iVOCs), yet their true atmospheric impact remains poorly constrained. In this study, we primarily employed an oxidation flow reactor (OFR) to simulate the atmospheric aging of emissions from compacted fresh PG-64-22 asphalt pucks under controlled laboratory conditions. Secondary organic aerosol (SOA) formation was monitored in real time using particle-phase instrumentation. In parallel, VOCs and iVOCs were collected on sorbent tubes for subsequent thermal desorption and analysis by flame ionization detection and mass spectrometry.

Our results show that while emissions are strongly temperature-dependent, both SOA mass yields and total VOC release rates are significantly lower than previously reported. At 60°C, we estimate that total asphalt-related SOA emissions across Los Angeles County contribute only ~0.131 kg/day, which is less than 0.0016% of total SOA reported in the 2022 AQMP. In contrast to prior work (e.g., Khare et al., 2020), which assumed complete binder accessibility and estimated a 0.1% binder mass loss, our data suggest a worst-case lifetime loss of only ~0.0025%. When applying a more realistic exponential decay model, the projected lifetime loss is ~0.00014%, which is over 700 times lower than earlier estimates. These discrepancies are due to earlier assumptions of full binder accessibility. This work emphasizes the importance of incorporating physically realistic, time-dependent emission behavior into urban VOC inventories and offers a refined understanding of asphalt's contribution to atmospheric chemistry.