科研之友
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摘要
A new condensed gas-phase isoprene mechanism is developed and evaluated, using O-3, nitrogen oxides (NOx), and volatile organic compounds (VOC) data from over twenty isoprene experiments. Experiments were performed in two UNC dual outdoor smog chambers using natural sunlight, with different NOx levels, and with or without the presence of an urban hydrocarbon environment. The mechanism uses the Carbon Bond mechanism (CB05) to represent inorganic chemistry and hydrocarbons other than isoprene. It was designed so that the chemistry related to secondary organic aerosol (SOA) formation can be incorporated, and thus it can be further expanded into a gas-aerosol-phase mechanism. A box model framework of this new isoprene mechanism is able to reasonably simulate most experimental data at HC/NOx ratios that range from 0.3 to 18. An intercomparison was performed between the isoprene kinetics developed in this study and other isoprene chemistry that is included in other kinetic mechanisms, including MCM v3.1, SAPRC99, SAPRC07, MIM2, CB4 and CB05. The results indicate that most current mechanisms tend to under-predict ozone levels to different extents, while the new mechanism simulates the UNC smog chamber O-3 data better than the others in most cases, especially at higher HC/NOx ratios. Further, the new mechanism performs reasonably well in modeling outdoor smog chamber experiments with isoprene in an urban hydrocarbon mixture. In addition, a HOx (OH + HO2) recycling scheme based upon Peeters et al. (2009) and Archibald et al. (2010b) was implemented in MCM v3.1 and the new UNC mechanism, since it has been recently been suggested to be very important under low-NOx conditions. Although our experimental data base is very limited for the low-NOx condition, the Peeters et al. (2009) isoprene chemistry tended to significantly over-predict observed chamber O-3. This suggests that more low-NOx experiments and further confirmation of current theoretical studies are needed.
- 出版日期2011-8
- 单位山东大学
