京津冀区域是我国大气复合污染的“重灾区”，随着“大气国十条”与"北京市清洁空气行动计划"等政策落实，区域空气质量明显改善，然而多个城市PM2.5浓度仍超出国家标准。二次无机气溶胶对灰霾事件形成有显著影响，已成为我国大气复合污染深入治理亟待解决的关键问题。本研究以京津冀地区为研究对象，针对典型城市开展二次无机组分观测实验，结合历史观测数据，探究2013-2021年二次无机组分污染成因机制与变化趋势；基于高分辨率排放清单与本地化源成分谱，应用气象与空气质量模型，建立观测-模拟耦合的前体物二次转化评价方法，揭示不同排放结构城市前体物转化特征及变化趋势；重点聚焦重污染时段前体物与二次组分响应关系及变化趋势，开展气象-排放交叉情景模拟，识别污染物减排、气象要素与前体物转化、二次无机气溶胶浓度响应关系，理清二次无机气溶胶生成主要影响因素。研究成果可为我国下一阶段复合污染深入治理提供科学支撑。

Beijing-Tianjin-Hebei (BTH) region has been suffering the most serious air pollution issue among China. With the implementation of “Action plan on Air Pollution Prevention and Control” and “the Clean Air Action plan” released by Beijing and so on forth, the air quality of the region has achieved obvious improvement. However, the PM2.5 concentrations in urban areas still exceed the national standard. As the major contributors to fine particulate matter, secondary inorganic water-soluble ions have become a key issue to be solved urgently in the further control of air pollution. In this study, daily PM2.5 samples in typical cities of BTH will be collected, secondary inorganic aerosols will be analyzed. The formation mechanism and variation trend of secondary inorganic aerosols during 2013-2021 will be investigated combining the historical observation data. Based on high-resolution emission inventory and localized source component spectrum, a monitoring-modeling coupled method will be established applying the meteorological model and air quality model. The characteristics and variation trend of precursors conversion in different cities with various emission structures will be revealed. Multi-year meteorology-emission scenario simulation will be carried out in order to recognize the relationship among reduction of pollutant emissions, meteorological conditions, the convention degree of precursors and the improvement of secondary inorganic water-soluble ions pollution. The main factors affecting the formation of secondary inorganic aerosols will be clarified. The research achievement can provide scientific support for the next stage of atmospheric pollution control in China.