Heterogeneous Ozonolysis of Endocyclic Unsaturated Organic Aerosol Proxies: Implications for Criegee Intermediate Dynamics and Later-Generation Reactions

Abstract

Unsaturated low-volatile organic compounds have been observed in atmospheric aerosol particles (e.g., aerosols from plants, cooking, and biomass burning) and human skin. Understanding their chemical fates through reactions with ozone at the relevant interfaces is crucial to elucidating the multiphase chemical mechanisms and predicting their environmental and health impacts. In this work, heterogeneous ozonolysis of two endocyclic unsaturated organic aerosol proxies (4-cyclohexene-1,2-diacid and shikimic acid) were studied in a flow tube reactor under different O3 exposure levels and relative humidities (30%, 60%, and 90%). Our results show strong RH dependence for the oxidation kinetics due to aerosol phase state change and secondary chemistry (e.g., parent acids reacting with the produced Criegee Intermediates). The observed multifunctional products are explained by the various Criegee Intermediates mechanisms and later-generation reactions. Three processes that lead to the evolution of first-generation carbonyl products were revealed in light of independent measurements: (1) intramolecular aldol reactions; (2) peroxide oxidation of aldehydes (i.e., Baeyer–Villiger reactions); and (3) decarboxylation induced by hydrogen peroxide. Furthermore, organic peroxides were observed to form from accretion reactions between the Criegee Intermediates and the parent compounds as well as the later-generation multifunctional products. The proposed mechanisms can be a key extension to the current understanding of heterogeneous ozonolysis of unsaturated organic aerosol.

Effect of inorganic-to-organic mass ratio on the heterogeneous OH reaction rates of erythritol: implications for atmospheric chemical stability of 2-methyltetrols

“…The density of erythritol particles is estimated to be 1.173 g cm −3 , using the volume additivity rule with the density of water and erythritol (1.451 g cm −3 ) and particle composition (i.e., mass fraction of solute, mfs). The mfs is derived from the hygroscopicity data reported by Marsh et al 2017and is reported to be 0.47±0.02 at 85 % RH, which agrees well with model simulations (mfs = 0.482) using the Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients (AIOMFAC) model (Zuend et al, 2008(Zuend et al, , 2011. For erythritol-AS particles, the particle diameters were measured to be 278.2-281.5 nm before oxidation (Table 1).…”

Compositional Evolution of Secondary Organic Aerosol as Temperature and Relative Humidity Cycle in Atmospherically Relevant Ranges

“…The extraction procedures follow previous studies. 30,35,42 From the GC−MS measurements, four major α-pinene SOA tracers were detected and quantified, including pinonic acid (C 10 H 16 O 3 ), cis-pinic acid (C 9 H 14 O 4 ), 10-hydroxypinonic acid (C 10 H 16 O 4 ), and 3-hydroxyglutaric acid (C 5 H 8 O 5 ) ( Figure S2). 43,44 From the detailed IMS-TOF measurements under both the positive and negative ion modes, we observed a number of polar oxygenated compounds with chemical formulas consistent with previously reported α-pinene SOA monomeric and dimeric products.…”

“…38 SOA Compositions Measured by Offline Mass Spectrometry Techniques. Portions of the SOA filter samples were extracted for offline analyses by a gas chromatograph electron impact ionization mass spectrometer (GC−MS, Agilent Inc. 7890 GC and 5975 MSD) 35 and an electrospray ionization (ESI) ion mobility spectrometry timeof-flight mass spectrometer (IMS-TOF, Tofwerk Inc.) 39−41 to study the molecular compositions of the resultant SOA. The extraction procedures follow previous studies.…”

Dark air–liquid interfacial chemistry of glyoxal and hydrogen peroxide

“…11,12 HHPs are recently detected by APCI-MS/MS to study the SOA. 41,42 In situ detection of hydroperoxides suggests the oxidizing capacity of the aqueous surface exists even without UV light. The high Henry's law constant indicates that the HHPs has a high potential to partition into the aqueous phase, 43 further facilitating the uptake of VOCs and other trace gases onto the aqueous surface of clouds, fogs, or wet aerosols.…”