26 Feb 2021

26 Feb 2021

Review status: this preprint is currently under review for the journal ACP.

Revisiting the reaction of dicarbonyls in aerosol proxy solutions containing ammonia: the case of butenedial

Jack C. Hensley1, Adam W. Birdsall2,a, Gregory Valtierra3, Joshua L. Cox2, and Frank N. Keutsch1,2,4 Jack C. Hensley et al.
  • 1School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
  • 2Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
  • 3Harvard College, Cambridge, MA, USA
  • 4Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
  • anow at: Goodyear, Akron, OH, USA

Abstract. Reactions in aqueous solutions containing dicarbonyls (especially the α-dicarbonyls methylglyoxal, glyoxal, and biacetyl) and reduced nitrogen (NHx) have been studied extensively. It has been proposed that accretion reactions from dicarbonyls and NHx could be a source of particulate matter and brown carbon in the atmosphere and therefore have direct implications for human health and climate. Other dicarbonyls, such as the 1,4-unsaturated dialdehyde butenedial, are also produced from the atmospheric oxidation of volatile organic compounds, especially aromatics and furans, but their aqueous phase reactions with NHx have not been characterized. In this work, we determine a pH-dependent mechanism of butenedial reactions in aqueous solutions with NHx that is compared to α-dicarbonyls, in particular the dialdehyde glyoxal. Similar to glyoxal, butenedial is strongly hydrated in aqueous solutions. Butenedial reaction with NHx also produces nitrogen-containing rings and leads to accretion reactions that form brown carbon. Despite glyoxal and butenedial both being dialdehydes, butenedial is observed to have three significant differences in its chemical behavior: (1) as previously shown, butenedial does not substantially form acetal oligomers, (2) the butenedial/OH reaction leads to light-absorbing compounds, and (3) the butenedial/NHx reaction is fast and first order in the dialdehyde. Building off of a complementary study on butenedial gas-particle partitioning, we suggest that the behavior of other reactive dialdehydes and dicarbonyls may not always be adequately predicted by α-dicarbonyls, even though their dominant functionalities are closely related. The carbon skeleton (e.g., its hydrophobicity, length, and bond structure) also governs the fate and climate-relevant properties of dicarbonyls in the atmosphere. If other dicarbonyls behave like butenedial, their reaction with NHx could constitute a regional source of brown carbon to the atmosphere.

Jack C. Hensley et al.

Status: open (until 23 Apr 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Referee comment on acp-2021-137', Anonymous Referee #1, 31 Mar 2021 reply
  • RC2: 'Comment on acp-2021-137', Anonymous Referee #2, 01 Apr 2021 reply
  • RC3: 'Comment on acp-2021-137', Anonymous Referee #3, 08 Apr 2021 reply

Jack C. Hensley et al.

Model code and software

Code and raw data for analysis Jack Hensley

Jack C. Hensley et al.


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Short summary
We measured reactions of butenedial, an atmospheric dicarbonyl, in aqueous mixtures that mimic the conditions of aerosol particles. Major reaction products and rates were determined to assess their atmospheric relevance and to compare against other well-studied dicarbonyls. We suggest that the structure of the carbon backbone, not just the dominant functional group, plays a major role in dicarbonyl reactivity, influencing the fate and ability of dicarbonyls to produce brown carbon.