活性卤素物种BrO和IO对沿海地区自由基收支平衡与大气氧化性影响研究

Currently, the enhancement of atmospheric oxidation capacity is the core driving force of fine particle and ground surface ozone pollution in China. Comprehensive knowledge on the atmospheric oxidation capacity is the key to grasp the formation mechanism of regional complex air pollution. Reactive halogen species (RHS) are not only directly involved in the processes of atmospheric radical production and loss, but also can affect the sources and sinks of many important species. Therefore, RHS are considered to play a significant role in the tropospheric chemistry. However, there were rare researches focusing on the RHS and their chemical behaviors. Activities of RHS in the atmospheric oxidation capacity and complex pollution are need to be further explored urgently. In this study, the Differential Optical Absorption Spectroscopy (DOAS) method will be utilized to measure the BrO and IO concentrations at costal urban area and offshore island, respectively. Then the typical RHS levels in the continental and marine boundary layer of China eastern area are characterized along with its temporal variations. The impacts of RHS on the radical budget and atmospheric oxidation capacity are quantified based on the simulation by chemical transport model. Coupled with measured data and air pollution episodes, we will further diagnose the crucial chemical behavior of BrO and IO under different atmospheric conditions, especially for the interaction mechanism during the complex air pollution evolution. This study is beneficial to make up the gaps of related halogen chemistry research in China, and also critical to reveal the atmospheric radical chemistry and formation mechanism of regional complex air pollution.

大气氧化性增强是当前我国细颗粒物污染和近地面高浓度臭氧问题的核心驱动力，全面解析大气氧化能力成为掌握区域性复合型大气污染形成机制的关键。活性卤素物种直接参与大气自由基生消过程，影响许多重要物种的源和汇，在大气对流层化学中起着十分重要的作用。但目前关于活性卤素物种及其化学行为的探讨十分有限，其在大气氧化性与复合污染中的角色作用如何亟待研究。本项目拟利用差分吸收光谱技术在上海城区与近海岛屿开展BrO和IO浓度的全面监测，摸清我国东部地区海、陆边界层中活性卤素物种浓度水平及其变化特征。基于化学模型模拟，量化活性卤素物种对自由基收支平衡与大气氧化性的影响。结合观测资料与空气污染案例，诊断不同污染程度和环境条件下BrO、IO的关键化学行为，特别是在大气复合污染过程中的作用机制。该研究不仅有利于弥补我国卤素化学研究的相关空白，而且对揭示大气自由基化学、区域复合污染形成机制具有十分积极、重要的意义。

中国东部沿海是经济快速发展、人口快速增长的区域，随之而来的是高速发展带来的臭氧污染。活性卤素物种(RHS)作为消耗海洋边界层内臭氧的重要因素，相应的浓度监测及其源和汇的研究对于大气污染的防治具有十分重要的意义。此外，RHS在大气复合污染过程中起着重要作用，这涉及到卤素化学对活性自由基收支平衡及大气氧化性的影响，在国内却缺乏此类研究。鉴于此，本项目以我国东部沿海城市、近海岛屿为典型环境，利用连续、实时在线的光谱监测技术手段，定量研究和揭示活性卤素物种对自由基收支平衡和大气氧化能力的影响，取得的研究成果如下：（1）经过大量测试和光谱校正工作，建立了一套适用于中纬度海洋边界层与我国东部沿海区域的活性卤素光谱探测与浓度反演技术；（2）通过花鸟岛和崇明岛观测实验，掌握了中国东部近海岛屿和沿海城市岛屿中氧化溴（BrO）的浓度水平及其影响因素；（3）基于区域模式模拟和观测实验结果，发现了热带气旋过程对海洋边界层中BrO浓度的影响机制及其对陆地臭氧浓度的化学清除效应；（4）基于一维模型与区域模式探究了不同污染情景下卤素物种浓度特征，并对东亚海域和中国大陆地区的大气氧化剂（包含大气自由基）模拟，发现了卤素化学对不同氧化剂呈不同的效应，但是整体上对污染地区的大气氧化性具有明显的促进作用。