过渡金属催化氧化对我国东部硫酸盐影响研究

Increasingly severe and frequent winter haze has been hovering over East China in recent years. Sulfate aerosol is one of the major components of fine particle, partly responsible for the visibility decline during hazy days. In winter when the photochemistry is repressed and the overall atomspheric oxidizing capacity decreases, transition metal catalysis is likely to substantially enhance the formation of sulfate aerosol. Yet, quantitative study on this pathway is still quite limited. Based on seasonal measurement on transition metals and WRF-Chem (the Weather Research and Forecasting model coupled with Chemistry) model, we have revealed the significance of the catalyzed oxidation of dissolved surfer dioxide by transition metals in China. Nevertheless, low time-resolving measurements and direct use of overseas observations would introduce considerable uncertainties. Thus, this study will integrate high time-resolving in-situ measurements, trajectory analysis and chemical transport model (CTM) to investigate the enhancement role of transition metals in sulfate formation on the basis of the Station for Observing Regional Processes of the Earth System (SORPES) in the western part of the Yangtze River Delta. Here, long-term measurements and corresponding trajectories are combined to analyze the spatiotemporal variation of transition metal concentration as well as its correlation with sulfate aerosol. Meanwhile, the measurements will also be involved in the optimization of CTM so as to better quantify the contribution from transition metal catalysis to sulfate formation. This study is of great importance to get a better idea of high-concentration sulfate aerosol during winter haze events and impact of anthropogenic activities on regional climate change.

中国东部近年冬季灰霾污染频发，硫酸盐作为细颗粒物重要组分，其快速积累是能见度降低的原因之一。冬季弱大气氧化性条件下，过渡金属催化氧化过程可能是硫酸盐快速生成的重要途径，但对于该过程定量研究甚少。申请人前期已基于季节性过渡金属的观测和大气动力-化学耦合模式WRF-Chem揭示了铁锰催化氧化在中国的重要性，但低分辨率的观测难以反映特定时段的污染特征，国外过渡金属物化特性的直接套用也引入较大不确定性。由此，本项目拟在位于长三角超级观测站现有基础上，集合多参数实时在线观测和过程分析、空气质量模型等多种手段分析过渡金属催化氧化对硫酸盐生成影响。该研究创新之处为立足于连续高分辨率的观测，探讨过渡金属时空变化规律及其与硫酸盐生成的关系，同时利用外场观测优化数值模式，进一步分析过渡金属催化氧化过程的影响要素及其定量贡献。本项目的开展有助于更好认识我国灰霾期间高浓度硫酸盐产生原因及人类活动对区域气候的影响。

项目基本按照计划进度开展，2016至2017年在南京大学大气超级观测站年开展了为期两年的大气硫酸盐气溶胶及其气态前体物、过渡金属浓度的连续观测；2017至2018年基于项目期间和站点已有监测数据，针对2013年以来硫酸盐重污染事件，结合气象资料，从观测的角度分析硫酸盐污染过程。与此同时，收集整理已有的气象数据和大气成分观测资料，优化区域大气动力-化学耦合模式WRF-Chem中硫酸盐相关的参数化方案并开展多年模拟，针对大气硫酸盐气溶胶的来源、生成以及大气边界层和气溶胶相互影响、开展讨论分析。目前项目资助发表相关文章8篇，其中包括7篇大气科学领域一流期刊SCI论文7篇，培养研究生两名。