上海地区大气氨的时空分布及其对大气二次颗粒物生成的影响机制

氨气是影响二次细颗粒物生成的关键因子之一。然而，上海地区大气氨的时空分布及其对PM2.5生成的影响机制仍然十分不清楚。本项目拟采用外场观测和实验室模拟相结合的方式研究大气氨污染特征及其对上海大气细颗粒物形成的影响机制。具体地说，以URG法、MARGA法和被动采样法等手段在上海中心城区和周边远郊、典型污染源设点测定大气氨浓度。通过长期观测和强化观测系统表征上海大气氨的来源和时空分布。以MOUDI分级和MARGA在线，辅以吸湿性和密度测定表征上海大气细颗粒物的分级化学特征和变化过程。两者结合，揭示细颗粒物污染过程中氨气的作用机制以及气相凝结、非均相转化和低云输送的贡献。借助烟雾箱模拟，研究复杂气象和污染背景下，氨气影响二次细颗粒物生成的动力学机制，重点研究氨气对SO2等气态污染物非均相氧化的影响机制，细致考察环境湿度、氧化型离子等对反应速率的潜在影响。所得结果可为大气污染防治提供科学支撑。

o Atmospheric ammonia is of great importance in the secondary aerosol formation. it is not clear, however, that the spatial and temporal distribution of atmospheric NH3 and its strong impact on PM2.5. In this proposal, atmospheric NH3 concentration and its contribution to the PM2.5 formation are investigated. In detail, NH3 determination was deployed both in the downtown and suburb area by methods of URG, MARGA, and Ogawa passive sampler to obtain sources and spatial and temporal distributions of atmospheric NH3 in Shanghai.Size-fractionated distribution and temporal variation of chemical composition of PM2.5 are investigated using MOUDI cascade impactor and MARGA, in combination with hygroscopicity and density measurements. The imporatant role of NH3 on secondary aerosol formation and contribution of condensation, heterogeneous reaction and cloud transport to the PM2.5 will be revealed by combing these results. NH3 reaction dynamics on secondary aerosol formation under complex background is also investigated in a smog chamber. We focus on NH3 promoting effect on heterogeneous reaction mechanism of SO2, and reaction rate dependence on ambient RH and oxidized ions is also studied in detail.These reuslts can provide basic data for the prevention of atmosperic pollution in Shanghai.