Investigating the Effect of Temperature Cycles on Gas-Particle Phase Transitioning in Dark Ozonolysis Systems

DANIEL GONZALEZ, Chen Le, Ryan W. Drover, Huawei Li, Yanyu Zhang, Thomas Eckel, David R. Cocker III, University of California, Riverside

     Abstract Number: 290
     Working Group: Aerosol Chemistry

Abstract
This study investigates the impact of temperature cycles, after the formation of Secondary Organic Aerosol (SOA), in two dark ozonolysis systems: α-pinene and cyclohexene. The study challenges the conventional assumption that particle-gas phase partitioning is completely reversible during temperature cycles. The results reveal that temperature has a significant effect on SOA formation and highlights the need for improved understanding of the role of temperature in particle-gas phase partitioning and compound specific SOA formation. This understanding is essential for accurate modeling of atmospheric processes and air quality management strategies.

The study design is robust, with a multi-day indoor environmental chamber experiment conducted for the α-pinene system, and thermal cycling experiments performed for several consecutive days within a temperature range of 5 – 35°C. The α-pinene system exhibited consistent reversibility of gas-particle phase transitions upon repeated temperature cycling, while the cyclohexene system showed an irreversible loss of mass after the first temperature cycle, with consistent reversibility observed during subsequent temperature cycles. These findings, coupled with observations of the chemical (e.g., H:C, O:C, f43/f44) and physical nature (e.g., size, density, volatility) of the suspended aerosol, highlight the complex nature of atmospheric processes and the importance of understanding the impact of temperature on SOA formation.