Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published July 6, 2021 | Supplemental Material
Journal Article Open

Multigeneration Production of Secondary Organic Aerosol from Toluene Photooxidation


Photooxidation of volatile organic compounds (VOCs) produces secondary organic aerosol (SOA) and light-absorbing brown carbon (BrC) via multiple reaction steps/pathways, reflecting significant chemical complexity relevant to gaseous oxidation and subsequent gas-to-particle conversion. Toluene is an important VOC under urban conditions, but the fundamental chemical mechanism leading to SOA formation remains uncertain. Here, we elucidate multigeneration SOA production from toluene by simultaneously tracking the evolutions of gas-phase oxidation and aerosol formation in a reaction chamber. Large size increase and browning of monodisperse sub-micrometer seed particles occur shortly after initiating oxidation by hydroxyl radical (OH) at 10–90% relative humidity (RH). The evolution in gaseous products and aerosol properties (size/density/optical properties) and chemical speciation of aerosol-phase products indicate that the aerosol growth and browning result from earlier generation products consisting dominantly of dicarbonyl and carboxylic functional groups. While volatile dicarbonyls engage in aqueous reactions to yield nonvolatile oligomers and light-absorbing nitrogen heterocycles/heterochains (in the presence of NH₃) at high RH, organic acids contribute to aerosol carboxylates via ionic dissociation or acid–base reaction in a wide RH range. We conclude that toluene contributes importantly to SOA/BrC formation from dicarbonyls and organic acids because of their prompt and high yields from photooxidation and unique functionalities for participation in aerosol-phase reactions.

Additional Information

© 2021 American Chemical Society. Received: March 29, 2021; Revised: May 19, 2021; Accepted: May 20, 2021; Published: June 17, 2021. R.Z. acknowledged the support by the Robert A. Welch Foundation (Grant A-1417). Y.L. was supported by a dissertation Fellowship at Texas A&M University. The authors declare no competing financial interest.

Attached Files

Supplemental Material - es1c02026_si_001.pdf


Files (911.5 kB)
Name Size Download all
911.5 kB Preview Download

Additional details

August 20, 2023
October 23, 2023