State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China; State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex, Beijing 100084, China.
State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China; State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex, Beijing 100084, China.
Chemosphere. 2020 Sep;255:126907. doi: 10.1016/j.chemosphere.2020.126907. Epub 2020 Apr 30.
The downward transport of ozone (O) stemming from the stratosphere-to-troposphere exchange (STE) can be a significant contributor to background O. Such enhancement of background O may also influence ground-level PM, particularly in polluted regions which have abundant precursor emissions. In this study, we quantified the STE impact on tropospheric O and its subsequent influence on surface PM across the northern hemisphere. The sensitivity analyses was conducted by using a comprehensive hemispheric atmospheric modeling system. Results suggest the surface PM concentration can be considerably enhanced by the STE in polluted regions including East China, East US, and Europe, mostly in winter and spring. In winter, the PM concentrations in East China, East US, and Europe are estimated to be enhanced by 1.3%, 3.5% and 5.5% due to the STE. The STE-enhanced PM concentrations are typically higher on high pollution days suggesting likely increasing contributions in regions with the growing pollution levels. During the heavy polluted days, the PM concentrations in East China can be enhanced by 2.289 μg/m in winter and 2.034 μg/m in spring due to the STE. The STE-enhanced PM also exhibits strong diurnal variations following a pattern similar to the total PM concentration, with high increasing ratio in the morning and low at afternoon, suggesting that the enhancement is most pronounced during peak pollution events. The STE-enhanced PM is exclusively contributed by the increase of nitrate, ammonium, and secondary organic aerosol which in-turn are strongly influenced by the atmospheric oxidation capacity.
平流层至对流层交换（STE）导致的臭氧（O）向下输送可能是背景 O 的一个重要贡献者。这种背景 O 的增强也可能影响地面 PM，特别是在有丰富前体排放的污染地区。在这项研究中，我们量化了 STE 对对流层 O 的影响及其对北半球地面 PM 的后续影响。敏感性分析是通过使用全面的半球大气模拟系统进行的。结果表明，STE 可显著增强包括华东、美国东部和欧洲在内的污染地区的地表 PM 浓度，主要在冬季和春季。在冬季，由于 STE 的影响，预计中国东部、美国东部和欧洲的 PM 浓度将分别增强 1.3%、3.5%和 5.5%。STE 增强的 PM 浓度在高污染日通常更高，这表明在污染水平不断上升的地区，其贡献可能会增加。在重污染日，由于 STE 的影响，华东地区冬季 PM 浓度可增强 2.289μg/m，春季可增强 2.034μg/m。STE 增强的 PM 还表现出与总 PM 浓度相似的日变化规律，清晨增加比例较高，下午较低，表明在污染高峰期增强最为明显。STE 增强的 PM 仅由硝酸盐、铵盐和二次有机气溶胶的增加贡献，而这又受到大气氧化能力的强烈影响。
