Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 6583-6609, 2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
06 Jun 2017
Ozonolysis of α-phellandrene – Part 1: Gas- and particle-phase characterisation
Felix A. Mackenzie-Rae1, Tengyu Liu2,3,a, Wei Deng2,3, Sandra M. Saunders1, Zheng Fang2,3, Yanli Zhang2,4, and Xinming Wang2,4 1School of Molecular Sciences, The University of Western Australia, Crawley WA 6009, Australia
2State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
3University of Chinese Academy of Sciences, Beijing 100049, China
4Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
anow at: School of Energy and Environment, City University of Hong Kong, Hong Kong, China
Abstract. The ozonolysis of α-phellandrene, a highly reactive conjugated monoterpene largely emitted by Eucalypt species, is characterised in detail for the first time using a smog chamber at the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences. Gas-phase species were monitored by a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF), with yields from a large number of products obtained, including formaldehyde (5–9 %), acetaldehyde (0.2–8 %), glyoxal (6–23 %), methyl glyoxal (2–9 %), formic acid (22–37 %) and acetic acid (9–22 %). Higher mz second-generation oxidation products were also observed, with products tentatively identified according to a constructed degradation mechanism. OH yields from α-phellandrene and its first-generation products were found to be 35 ± 12 and 15 ± 7 %, respectively, indicative of prominent hydroperoxide channels. An average first-generation rate coefficient was determined as 1.0 ± 0.7  ×  10−16 cm3 molecule−1 s−1 at 298 K, showing ozonolysis as a dominant loss process for both α-phellandrene and its first-generation products in the atmosphere. Endocyclic conjugation in α-phellandrene was also found to be conducive to the formation of highly condensible products with a large fraction of the carbon mass partitioning into the aerosol phase, which was monitored with a scanning mobility particle sizer (SMPS) and a high-resolution time-of-flight aerosol mass spectrometer (AMS). Nucleation was observed almost instantaneously upon ozonolysis, indicating the rapid formation of extremely low-volatility compounds. Particle nucleation was found to be suppressed by the addition of either NO2 or a Criegee scavenger, with it being proposed that stabilised Criegee intermediates are important for new particle formation in the system. Aerosol yields ranged from 25 to 174 % depending on mass loadings, with both first- and second-generation products identified as large contributors to the aerosol mass. In short, with a high chemical reactivity and aerosol-forming propensity, α-phellandrene is expected to have an immediate impact on the local environment to which it is emitted, with ozonolysis likely to be an important contributor to the significant blue haze and frequent nocturnal nucleation events observed over Eucalypt forests.

Citation: Mackenzie-Rae, F. A., Liu, T., Deng, W., Saunders, S. M., Fang, Z., Zhang, Y., and Wang, X.: Ozonolysis of α-phellandrene – Part 1: Gas- and particle-phase characterisation, Atmos. Chem. Phys., 17, 6583-6609,, 2017.
Publications Copernicus
Short summary
The atmospheric decomposition of the biogenic α-phellandrene with ozone is characterised by conducting carefully controlled experiments in a smog chamber. Major gas-phase products are identified based on theoretical/mechanism insight, with yields quantified. Meanwhile, a significant amount of aerosol is formed and characterised, with Criegee intermediates found to be important for new particle formation. It is concluded that α-phellandrene contributes to aerosol formation/growth where emitted.
The atmospheric decomposition of the biogenic α-phellandrene with ozone is characterised by...