大气氧化能力增强是当前我国城市大气细颗粒物污染和春夏高浓度臭氧问题频发的重要驱动力，全面解析大气氧化能力是掌握我国区域性复合型大气污染形成机制的关键。大气自由基作为大气氧化能力的重要表征，其准确测量存在种种困难，所以开展自由基前驱物观测并评估其对大气氧化能力的影响成为一种重要且有效的手段。甲醛直接参与大气自由基源汇机制，是HOx自由基的重要前驱物，对大气氧化能力、区域大气污染具有重要影响。但目前关于城市大气甲醛光化学行为的探讨较为有限，亟待深入研究。因此，本项目拟利用光谱技术在大气污染严重的上海城区开展大气甲醛浓度的全面监测，建立适合城市区域的大气甲醛一次/二次来源示踪方法，研究城市大气甲醛浓度和来源特征；结合数值模拟，探究甲醛对大气自由基的贡献水平，量化其光化学反应对大气氧化能力的影响。该研究将有助于揭示大气自由基化学行为、区域复合污染形成机制，为制定城市大气污染控制措施提供科学依据。

The increasing of atmospheric oxidation capacity drove both the frequent pollution of fine particulate matter and high ozone levels in spring/summer at the urban area in China. Comprehensive knowledge on the atmospheric oxidation capacity is the key to resolve and clarify the formation mechanism of regional complex air pollution in domestic. Due to the difficulty in measure accurately of atmospheric free radical，the most typical representative of atmospheric oxidation capacity, observing the free radical precursor and evaluating its impacts on the atmospheric oxidation capacity become an important and effective way. Since formaldehyde engaged directly in source and sink of atmospheric free radical, it is the important precursor of HOx radical. Formaldehyde photochemical reactions are great importance of atmospheric oxidation capacity and regional air pollution. However, discussions about urban atmospheric formaldehyde photochemical reaction are still less involved and need to be further explored urgently. Therefore, this study aims to characterize the ambient formaldehyde concentration and source contribution, based on field observation via spectroscopic technique at a polluted urban area in Shanghai and establishment a proper primary/secondary source tracing method. Combined numerical simulation means, it also focuses on the contribution of formaldehyde on the atmospheric free radical and quantifying the influences on the atmospheric oxidation capacity. This research not only are helpful to dig out the chemical behavior of atmospheric free radical and formation mechanism of regional complex air pollution but also provide the scientific basis for the urban air pollution control measures.