黑碳气溶胶与边界层相互作用对中国东部近地面臭氧及其源汇关系的影响机制研究

At present, Ozone and aerosol coexisting in atmosphere is the main characteristic of the “complex air pollution” in Eastern China. Meanwhile, they can also affect with each other via complex physical and chemical processes. As one of the most important light-absorption aerosol, the radiation property of black carbon (BC) can influence the development of boundary layer, and then the influenced boundary layer affects the air quality. However, the systematic study on the impact of this interaction between BC and boundary layer on surface ozone is still lacking. In this project, two “one-year” simulations (one is with BC and the other one is without BC) on the meteorology and air pollutants in Eastern China will be conducted by the Weather Research and Forecasting with Chemistry (WRF-Chem) model coupled with the ozone tagging method which developed by proposer. Combined with the observational data and the processes analysis, the impacts of the interactions between BC and boundary layer on ozone contributions from the various physical and chemical processes in different seasons will be studied. Then, it will be revealed that the influence mechanism of the BC and boundary layer interaction on surface ozone over Eastern China. Based on the studies above, the impact and its seasonal variations of the BC and boundary layer interaction on the source-sink relationship of surface ozone over Easter China will also be studied. The findings of this project will help us to understand more about the impact mechanisms of aerosol on ozone and provide scientific basis for the synergistic treatment of ozone and aerosol pollutions.

当前我国东部大气复合污染的主要特征表现为气溶胶和臭氧并存于大气之中。与此同时，两者还会通过复杂的物理和化学过程对彼此产生影响。作为重要的吸收性气溶胶，黑碳的辐射特性能够改变边界层的发展特征，进而影响空气质量。然而这种黑碳与边界层的相互作用对近地面臭氧及其源汇关系的影响还缺乏系统而深入的机理研究。本项目拟使用耦合了申请人自主研发的臭氧源追踪技术的大气化学耦合模式WRF-Chem，以有黑碳和无黑碳两种情景分别对中国东部进行一个完整年的数值模拟。结合多种观测资料、过程量分析等，定量研究不同季节黑碳与边界层相互作用对臭氧各物理化学过程量的影响，进而系统地揭示黑碳对中国东部近地面臭氧的影响机制。在此基础上，阐明黑碳与边界层相互作用对中国东部典型城市近地面臭氧源汇关系的影响及其季节性差异。本项目的研究成果能更加深入的认识气溶胶对臭氧的影响机制，为臭氧和气溶胶污染协同治理提供科学的理论依据。

我国东部当前的大气污染特征表现为气溶胶和臭氧并存的复合型污染。黑碳气溶胶与边界层的相互作用会导致边界层的发展受到抑制，同时又会使气溶胶浓度累积造成空气质量的恶化。然而，黑碳与边界层的相互作用对臭氧及其源汇关系的影响机制尚不清楚。本项目基于耦合了项目负责人自主研发的臭氧源追踪技术的在线大气化学模式WRF-Chem，定量研究了黑碳与边界层相互作用对臭氧影响的理化机制以及对臭氧源汇关系的影响。研究发现：边界层发展的抑制作用导致臭氧前体物在边界层内的累积，并引起臭氧光化学生成量的少量增加；边界层发展的抑制作用弱化了垂直混合作用的强度但延长了其对近地面臭氧影响的时间。这造成正午前高空臭氧向近地面的传输减少，导致近地面臭氧在此时段浓度的降低，正午后高空的臭氧仍在向近地面传输，最终导致近地面臭氧浓度的恢复。黑碳与边界层的相互作用导致本地及周边地区对中午前的近地面臭氧的贡献减少，而正午后在臭氧浓度的恢复阶段，来自较远源区的臭氧从高空通过垂直混合运动到达地面，对近地面臭氧的贡献增加。本项目成果有助于更加深入地剖析气溶胶对臭氧及其源汇关系的影响机制，为我国东部气溶胶和臭氧的协同治理工作提供科学的理论依据。