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Published April 20, 2021 | Supplemental Material + Published
Journal Article Open

Unexpected Oligomerization of Small α-Dicarbonyls for Secondary Organic Aerosol and Brown Carbon Formation


Large amounts of small α-dicarbonyls (glyoxal and methylglyoxal) are produced in the atmosphere from photochemical oxidation of biogenic isoprene and anthropogenic aromatics, but the fundamental mechanisms leading to secondary organic aerosol (SOA) and brown carbon (BrC) formation remain elusive. Methylglyoxal is commonly believed to be less reactive than glyoxal because of unreactive methyl substitution, and available laboratory measurements showed negligible aerosol growth from methylglyoxal. Herein, we present experimental results to demonstrate striking oligomerization of small α-dicarbonyls leading to SOA and BrC formation on sub-micrometer aerosols. Significantly more efficient growth and browning of aerosols occur upon exposure to methylglyoxal than glyoxal under atmospherically relevant concentrations and in the absence/presence of gas-phase ammonia and formaldehyde, and nonvolatile oligomers and light-absorbing nitrogen-heterocycles are identified as the dominant particle-phase products. The distinct aerosol growth and light absorption are attributed to carbenium ion-mediated nucleophilic addition, interfacial electric field-induced attraction, and synergetic oligomerization involving organic/inorganic species, leading to surface- or volume-limited reactions that are dependent on the reactivity and gaseous concentrations. Our findings resolve an outstanding discrepancy concerning the multiphase chemistry of small α-dicarbonyls and unravel a new avenue for SOA and BrC formation from atmospherically abundant, ubiquitous carbonyls and ammonia/ammonium sulfate.

Additional Information

© 2021 The Authors. Published by American Chemical Society. ACS AuthorChoice. Received: November 29, 2020; Revised: February 23, 2021; Accepted: February 24, 2021; Published: March 16, 2021. Y.J. acknowledges the support by the National Natural Science Foundation of China Grants (41731279 and 41675122), Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01Z032), Natural Science Foundation of Guangdong Province, China (2019B151502064), and Science and Technology Program of Guangzhou City (201707010188). R.Z. acknowledges the support by the Robert A. Welch Foundation (Grant A-1417). Y.L. was supported by a dissertation Fellowship at Texas A&M University. Author Contributions: Y.L. and Y.J. contributed equally to this work. R.Z. conceived and supervised the work. Y.L. designed the experimental system and protocols and collected data. R.Z. and Y.L. drafted and revised the manuscript. J.H.S. helped draft and revise the manuscript. All authors analyzed the data, approved the final version, and agreed to be accountable for all aspects of the work. The authors declare no competing financial interest.

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Published - acs.est.0c08066.pdf

Supplemental Material - es0c08066_si_001.pdf


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Additional details

August 20, 2023
October 23, 2023