Molecular composition of organic aerosols formed in the α‐pinene/O₃ reaction: Implications for new particle formation processes

Abstract

Abstract. The molecular composition of particle phase ozonolysis products of o•-pinene is investigated to comprehend the aerosol formation process following the VOC oxidation, focusing on an understanding of new particle formation. Two analytical approaches are applied to identify lowvolatile oxidation products in the particle phase; off-line investigations using preconcentration on Tenax TA © followed by solvent extraction and liquid chromatography/mass spectrometry as well as an on-line technique, in which the organic aerosols are introduced directly into the ion source of a mass spectrometer (atmospheric pressure chemical ionization / mass spectrometry (APCI/MS)). Both techniques showed the formation of difunctional carboxylic acids, compounds whose physico-chemical properties will govern most of their mass into the particle phase. Furthermore, stable binary diacid adducts could be identified by MSn-experiments. These observations might give insight into the process of new particle formation by heteromolecular homogeneous nucleation, indicating that the initial cluster formation cannot be described by macroscopic properties of single oxidation products. Instead, strong intermolecular forces between different diacids might play a key role in the formation of initial nuclei and their subsequent growth.

Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part A): tropospheric degradation of non-aromatic volatile organic compounds

“…However, attention is also being given to expanding the coverage of biogenic VOC to include additional terpenes and oxygenates, and a representation of gas-aerosol partitioning of the oxidised products of monoterpene degradation is being developed to assist interpretation of the formation of secondary organic aerosol observed in chamber studies (e.g. Hoffmann et al, 1997;BIOVOC, 1998;Yu et al, 1999;Jang and Kamens, 1999;Cocker et al, 2001). …”

“…In the α-and β-pinene schemes, the following isomerisation reactions are included in competition with alternative decomposition routes: These reactions were included to allow the formation of the identified products pinic acid from α-and β-pinene degradation and 10-hydroxypinonic acid from α-pinene degradation (e.g. Christoffersen et al, 1998;Hoffmann et al, 1998;Jang and Kamens, 1999;Glasius et al, 2000), as described by . Reaction (25) for the complex acyl-oxy radical is assigned a probability of 80%, with the remaining 20% decomposing to eliminate CO 2 and an organic radical (in accordance with the reaction assumed for acyl-oxy radicals in general).…”

“…However, it is well established that the degradation of each emitted VOC occurs by a unique mechanism (because of differences in reactivity and structure), such that the relative contributions of VOC to the formation of ozone and other secondary pollutants varies from one compound to another (e.g. Carter and Atkinson, 1987;Grosjean and Seinfeld, 1989;Derwent and Jenkin, 1991). Over the past two decades, the availability of kinetic and mechanistic data to help elucidate the degradation mechanisms of VOC has increased significantly, and various aspects of the tropospheric chemistry of organic compounds have been reviewed extensively (e.g.…”

Role of the reaction of stabilized Criegee intermediates with peroxy radicals in particle formation and growth in air

“…Several pathways leading to oligomer formation have been suggested, including (i) reactions of stabilized Criegee intermediates (SCI) with carboxylic acids and carbonyls, forming a-acyloxy hydroperoxides and secondary ozonides, respectively; 12,15,[18][19][20] (ii) reactions of monomer products from ozonolysis, e.g., aldol condensation, peroxyhemiacetal formation, gem-diol formation, esterification, acetal and hemiacetal formation; 13,16,18,[21][22][23][24][25][26] and (iii) formation of non-covalently bound dimer clusters of carboxylic acids. 21,[26][27][28] Pathway (i) is thought to take place in the gas phase, and pathway (ii) is suggested to occur mainly on the surface or within the bulk of SOA particles, whereas pathway (iii) may occur in both phases. Quite recently, gas phase formation of esters 17 and highly oxidized products (termed extremely low-volatility organic compounds, ELVOCs) [29][30][31][32] have been suggested in the a-pinene/O 3 system.…”

High-molecular-weight esters in <i>α</i>-pinene ozonolysis secondary organic aerosol: structural characterization and mechanistic proposal for their formation from highly oxygenated molecules

“…A high-molecular-weight compound with a molecular weight (MW) of 358 was reported for the first time by Hoffmann et al (1998) in α-pinene/O 3 SOA using off-and online mass spectrometry (MS). With online atmospheric pressure chemical ionization (APCI) MS it was shown that this compound is formed concomitantly with two monomers, i.e., cis-pinic acid and a MW 172 compound that was tentatively identified as norpinic acid.…”