北京市区夏季O3生成过程分析

采用三维空气质量模型CMAQ-MADRID对北京地区夏季O3进行模拟,利用过程分析模块IPR和IRR研究北京市区大气O3的生成过程,重点分析自由基循环和NOx循环的量化特征.结果表明,市区整个边界层具有较强的大气氧化性,O3生成呈现VOC控制的特征.边界层内O3大气化学过程存在垂直差异,O3生成高值区在200～800m之间,近地层O3浓度升高主要依赖边界层内高层大气O3的垂直输送.NOx排放集中在近地层,新NO注入量较高,NOx循环次数仅为1.3,O3生成量很低.边界层上层大气从低层获得NOx,由于新NO注入量较低,同时上层大气保持了较强的大气氧化性,NOx循环次数达到5.0,O3生成量较高.

Process analysis of O3 formation in summer at Beijing

A three dimension air quality model CMAQ-MADRID was employed to simulate O_ 3 pollution in summer at Beijing. IPR and IRR, modules of process analysis in CMAQ, were used to explore the O_ 3 building process in urban area with focus on radical and NO_x cycles. In urban area, strong oxidation capacity was spread to full boundary layer, and O_ 3 formation was in VOC-limited regime. Obvious discrepancy of O_ 3 building process existed between surface layer and upper level of boundary layer, with high O_ 3 production rate at altitude of 200~800 m, and the high O_ 3 concentration at surface layer mainly came from O_ 3 vertical transportation of upper air. Since NO_x emission was concentrated at surface layer, new NO input was quite high and NO_x chain length was only 1.3, resulting in a low O_ 3 yield. At upper level of boundary layer, where the oxidation capacity was strong and new NO input was low, NO_x chain length reached 5.0, thus O_ 3 yield there was rather high.