研究大气过氧乙酰基硝酸酯（PAN）和O3污染水平、季节变化特征以及前体物VOCs的光化学生成潜势对评估其大气环境和人体健康影响具有重要科学意义。目前，我国缺乏相关研究。基于申请人前期的研究成果，本项目拟对北京市大气PAN、O3、VOCs等气态污染物、颗粒物质量浓度、粒子数和粒径分布、光解系数以及常规气象要素等开展同步观测，获得北京市不同季节大气光化学污染水平和变化特征，着重分析夏季、秋冬季各气态污染物之间的相关关系和日变化规律，通过研究气象因素对PAN、O3和其他气态污染物浓度变化的影响，结合数值模拟区分远距离水平传输、垂直输送以及局地光化学生成过程的贡献，继而利用基于观测资料的模型(OBM)定量研究不同季节大气PAN和O3的光化学过程和对前体物VOCs的敏感性，甄别出不同季节各自的关键化学过程和关键物种，为制定有效的光化学污染控制措施提供科学理论依据。

For assessing the effect of atmospheric peroxyacetyl nitrate (PAN) and ozone (O3) on environment and human health, it’s crucial to investigate their pollution levels, seasonal variations, and their photochemical creation potentials for their respective precursors VOCs. By far, there is lack of related researches in China. Based on our previous studies, we will conduct the simultaneous measurements of atmospheric gaseous pollutants such as PAN, O3, volatile organic compounds (VOCs), and other gases, particle matter sizes distribution and count, photolysis frequencies, and common meteorological factors, to obtain the photochemical pollution levels and their seasonal variations in Beijing, and especially to investigate their correlations and diurnal variations during summer and autumn-winter. In addition, we also will analyze the effects of meteorological factors on these gaseous pollutions to partition the contributions of the local photochemical formation, horizontal and vertical transport by using numerical simulation. Then, we will quantitatively investigate the photochemical processes of PAN and O3 and the sensitivity to their own precursors VOCs to find their respective key processes and key precursors during different seasons by using an Observational Based Model. It’s aimed to provide scientific theoretical basis for making an effective controlling measure for the photochemical pollution.