柴达木盆地典型盐湖边界层活性溴氧自由基的分布探测和化学过程研究

As important atmospheric reactive halogen species, BrO radicals are known to play key roles in multiple troposphere chemical reactions and change the atmosphere oxidizability. As the critical area for atmospheric BrO research, researches of boundary layer BrO above salt lakes and salt pans on the release mechanisms, sources and the depletion mechanisms on boundary layer ozone become frontier of the atmospheric research. However, up to now, there is still few in-situ observation of boundary layer BrO at typical salt lake area in China. Furthermore, because of the low background concentration (about 1E12) and active chemical property of atmospheric BrO, traditional observing methods were unable to reflect the actual condition..Here we plan to carry out the ground-based MAX-DOAS observations of boundary layer BrO at Qaidam Basin with high resolution. From these measurements, continues and real time variation of BrO column densities will be derived and the rule of distribution will be analyzed. By means of this project, the source, sink and the release mechanisms of BrO will be systematically analzed and discussed. Further study will be carried out on ozone depletion mechanisms and environment influence of halogen oxides in troposphere.

活性卤氧自由基参与大气中多种化学过程，对对流层大气的氧化性有重要影响。盐湖地区是大气活性卤氧自由基研究的关键区域，对盐湖及周边盐沼边界层大气BrO、IO等的产生机制及其对边界层臭氧的化学破坏过程的研究已成为近年来对流层大气研究的重要前沿。然而，目前对我国典型盐湖地区对流层活性卤氧自由基的近地观测仍十分有限，而且由于其活性较强且在大气中的浓度很低（1E-12量级），对观测技术也提出了很高的要求。.本项目拟通过高分辨的地基多轴被动差分吸收光谱（MAX-DOAS）技术，对我国柴达木盆地典型盐湖边界层BrO等进行直接在线观测，获得BrO等浓度的连续、实时变化和分布信息，了解盐湖溴组分的分布规律。同时，深入探究盐湖边界层BrO的形成机制、源汇分布和变化因素，揭示活性卤素氧化物的反应机理，为研究对流层臭氧损耗机制、评估对流层卤氧化合物的环境效应提供依据。

本项目构建了高精度二维被动差分吸收光谱系统，并首次在我国柴达木盆地8个典型盐湖区域开展了对流层溴氧自由基的实时观测，获得了盐湖表面BrO的柱浓度、混合比和时空分布特征。根据下垫面理化性质和环境要素分析，阐明了影响BrO产生和分布的影响因素，通过量子化学计算构建了活性溴氧自由基在盐湖表面的主要形成机制模型，并采用动力学计算模拟了该过程中对流层臭氧的损耗和活性Br的产生，评估了我国柴达木盆地盐湖溴的释放量及对大气氧化性和生态环境的影响。本项目为更好的理解盐湖边界层活性溴氧自由基的源汇机制，揭示盐湖边界层大气氧化性变化提供了科学依据。