基于MAX-DOAS观测的北极地区对流层BrO的分布和变化机制探索

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, Arctic circum area has been paid extensive attentions. Thereby, researches of tropospheric BrO around Arctic area on the generation 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 atmospheric BrO at Ny-?lesund. Uncertainties still exist on the distribution, release mechanisms and atmospheric environment effect of regional reactive bromine compounds. 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 and ship-board MAX-DOAS observations of troposphere BrO at Ny-?lesund and the Arctic Ocean separately. 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, and the environment influence will be evaluated. Further study will be carried out on tropospheric ozone depletion mechanisms in polar regions.

BrO参与对流层大气中多种化学过程，改变大气氧化性，是大气中重要的活性卤素化合物。北极地区是大气BrO研究的关键区域，对北极及周边地区大气对流层BrO的产生机制以及BrO对极地边界层臭氧的化学破坏过程的研究已成为近年来极地大气研究的重要前沿。然而，目前对北极地区对流层BrO的近地观测仍十分有限，而且由于BrO的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多轴被动差分吸收光谱（MAX-DOAS）技术，在北极新奥尔松地区和北冰洋海冰覆盖区分别采用地基和船基的方式开展对流层BrO的在线观测，获得北极区域BrO浓度的连续、实时变化和垂直分布信息，了解北极地区对流层BrO的分布规律。通过本项目的研究，系统地描绘北极地区对流层BrO的源汇分布和变化趋势，揭示BrO的产生机制和变化因素，继而为进一步研究极区对流层臭氧损耗机制提供依据。

本项目采用地基被动多轴差分吸收光谱方法对北极新奥尔松地区BrO等痕量气体柱浓度进行了连续探测，完成了适用于极地地区的痕量气体遥测系统构建，优化了卤氧自由基的反演算法，连续观测结果高分辨得捕捉到了2015年春夏极地边界层特有的溴氧自由基爆发过程，为研究北极地区卤氧自由基的源汇分布和反应机制提供了宝贵的科学依据。结果显示，在臭氧损耗事件期间边界层BrO高达约50ppt。通过结合海冰、气象数据和后向轨迹模型计算，认为BrO爆发与海冰分布和气团来源有关，控制因素复杂，BrO的储库形式主要与海水盐度和pH值有关。结合地面臭氧和气态汞的变化，分析了溴爆发对当地大气氧化性和生态环境的影响。本项目为更好的理解极地边界层活性卤素物质的化学过程，完善活性卤素化合物源汇机制模型的关键参数，揭示极地边界层大气氧化性变化过程提供了依据。