Functionality-based formation of secondary organic aerosol from m-xylene photooxidation Academic Article uri icon

abstract

  • Abstract. Photooxidation of volatile organic compounds (VOCs) produces condensable oxidized organics (COOs) to yield secondary organic aerosol (SOA), but the fundamental chemical mechanism for gas-to-particle conversion remains uncertain. Here we elucidate the production of COOs and their roles in SOA and brown carbon (BrC) formation from m-xylene oxidation by simultaneously monitoring the evolution of gas-phase products and aerosol properties in an environmental chamber. Four COO types with the distinct functionalities of dicarbonyls, carboxylic acids, polyhydroxy aromatics/quinones, and nitrophenols are identified from early-generation oxidation, with the yields of 25%, 37%, 5%, and 3%, respectively. SOA formation occurs via several heterogeneous processes, including interfacial interaction, ionic dissociation/acidbase reaction, and oligomerization, with the yields of (204)% and (327)% at 10% and 70% relative humidity (RH), respectively. Chemical speciation shows the dominant presence of oligomers, nitrogen-containing organics, and carboxylates at high RH and carboxylates at low RH. The identified BrC includes N-heterocycles/N-heterochains and nitrophenols, as evident from reduced single scattering albedo. The measured uptake coefficient () for COOs is dependent on the functionality, ranging from 3.7104 to 1.3102. A functionality-based kinetic framework is developed to predict SOA production from the observed concentrations and uptake coefficients for COOs, which reproduces the measurement from m-xylene oxidation. Our results reveal that photochemical oxidation of m-xylene represents a major source for SOA and BrC formation under urban environments, because of its large abundance, high reactivity with OH, and high yields for COOs.

published proceedings

  • ATMOSPHERIC CHEMISTRY AND PHYSICS

author list (cited authors)

  • Li, Y., Zhao, J., Gomez-Hernandez, M., Lavallee, M., Johnson, N. M., & Zhang, R.

complete list of authors

  • Li, Yixin||Zhao, Jiayun||Gomez-Hernandez, Mario||Lavallee, Michael||Johnson, Natalie M||Zhang, Renyi

publication date

  • August 2022