Preprints
https://doi.org/10.5194/acp-2021-951
https://doi.org/10.5194/acp-2021-951
 
15 Dec 2021
15 Dec 2021
Status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Functionality-Based Formation of Secondary Organic Aerosol from m-Xylene Photooxidation

Yixin Li1,2, Jiayun Zhao1, Mario Gomez-Hernandez1, and Renyi Zhang1,3 Yixin Li et al.
  • 1Department of Chemistry, Texas A&M University, College Station, TX 77843, USA
  • 2Department of Chemistry, University of California Irvine, Irvine, CA 92697, USA
  • 3Department of Atmospheric Sciences, Texas A&M University, College Station, TX 77843, USA

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 simultaneous monitoring the evolutions 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/acid-base reaction, and oligomerization, with the yields of (20 ± 4) % and (32 ± 7) % at 10 % and 70 % relative humidity (RH), respectively. Chemical speciation shows the dominant presence of oligomers, nitrogen-containing organics, and carboxylates at 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 (γ) for COOs is dependent on the functionality, ranging from 3.7 × 10−4 to 1.3 × 10−2. A kinetic framework is developed to predict SOA production from the concentrations and uptake coefficients for COOs. This functionality-based approach well reproduces SOA formation from m-xylene oxidation and is broadly applicable to VOC oxidation for other species. 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.

Yixin Li et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-951', Anonymous Referee #1, 06 Jan 2022
  • RC2: 'Comment on acp-2021-951', Anonymous Referee #3, 16 Mar 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-951', Anonymous Referee #1, 06 Jan 2022
  • RC2: 'Comment on acp-2021-951', Anonymous Referee #3, 16 Mar 2022

Yixin Li et al.

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Short summary
Here we elucidate the production of COOs and their roles in SOA and brown carbon (BrC) formation from m-xylene oxidation by simultaneous monitoring the evolutions of gas-phase products and aerosol properties in an environmental chamber. A kinetic framework is developed to predict SOA production from the concentrations and uptake coefficients for COOs. This functionality-based approach well reproduces SOA formation from m-xylene oxidation and is applicable to VOC oxidation for other species.
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