期刊
ENVIRONMENTAL SCIENCE & TECHNOLOGY
卷 45, 期 11, 页码 4763-4770出版社
AMER CHEMICAL SOC
DOI: 10.1021/es104398s
关键词
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资金
- Office of Science (BES), U.S. Department of Energy [DE-FG02-08ER64529]
- U.S. EPA STAR [R833746]
- Pacific Northwest National Laboratory Aerosol Climate Initiative
- DOE by Battelle Memorial Institute [DE-AC06-76RLO 1830]
- NASA
- EPA [909255, R833746] Funding Source: Federal RePORTER
Chemical mechanisms for the production of secondary organic material (SOM) are developed in focused laboratory studies but widely used in the complex modeling context of the atmosphere. Given this extrapolation, a stringent testing of the mechanisms is important. In addition to particle mass yield as a typical standard for model-measurement comparison, particle composition expressed as O:C and H:C elemental ratios can serve as a higher dimensional constraint. A paradigm for doing so is developed herein for SOM production from a C-5-C-10-C-15 terpene sequence, namely isoprene, a-pinene, and beta-caryopyhllene. The model MCM-SIMPOL is introduced based on the Master Chemical Mechanism (MCM v3.2) and a group contribution method for vapor pressures (SIMPOL). The O:C and H:C ratios of the SOM are measured using an Aerosol Mass Spectrometer (AMS). Detailed SOM-specific AMS calibrations for the organic contribution to the H2O+ and CO+ ions indicate that published O:C and H:C ratios for SOM are systematically too low. Overall, the measurement-model gap was small for particle mass yield but significant for particle-average elemental composition. The implication is that a key chemical pathway is missing from the chemical mechanism. The data can be explained by the particle-phase homolytic decomposition of organic hydroperoxides and subsequent alkyl-radical-promoted oligomerization.
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