Based on brief overview of air quality status during APEC, The variation features of air quality are analyzed in various aspects, including year-on-year analysis of pollutants concentration, analysis on percentage distribution and changing characteristics of hourly pollutants concentrations on different sites in different regions, analysis on changing features of daily pollutants concentrations, variation distribution of air quality improvement effects, and so on. Through these analysis, the impacts on pollution levels and features influenced by different control measures during APEC could be investigated, and major impact factors of air quality and contributions of various control measures in terms of improving air quality are assessed quantitatively and qualitatively via methods of chemical composition analysis and models establishment. The study shows that in the period of APEC, air quality improved substantially and almost fell in the classifications of excellent and good with great drop of pollutants concentrations;percentage distribution of hourly concentrations of all pollutants between control period of APEC and non control periods are extremely different;low daily pollutants concentration levels last longer and increased more slowly.%在简要回顾APEC期间的空气质量情况的基础上，从多方面较系统的分析了APEC期间北京市空气质量的变化特征，包括各项污染物浓度水平的同比分析、不同区域不同类别站点小时浓度的百分数分布及变化情况分析、污染物日变化规律变化特征分析、空气质量改善效果的空间分布特征分析、颗粒物组分变化特征分析、污染来源解析模型、数值污染模型等方法，力求从多个方面深入了解APEC控制措施对北京市污染水平、污染特征造成的影响，并利用组分、模型等方法定性定量的评估主要空气质量影响因素、不同的污染控制措施对APEC期间空气质量改善的作用及贡献。结果表明，APEC期间，北京市空气质量得到明显改善，空气质量基本处于优良级别，各项污染物浓度大幅下降，APEC污染控制期各项污染物的百分位数浓度与无控制期出现明显分离特征，污染物的日变化低浓度持续时间更长且增长更缓慢。
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