大气冰核微生物对灰霾形成的影响机制

Haze episodes characterized by high concentrations of particulate matter are the serious air pollution problems in major Chinese cities today. It was generally found that microorganisms are an important components of haze particles (10^5~10^7/m^3), and haze affects the abundance, activity and species of airborne microorganisms. However, the study on the microbial function and their impact on haze formation is currently lacking. According to our previous research that the abundance of ice-nucleating bacteria increased during the haze day compared with clean day, and their functions as cloud condensation nuclei and ice nuclei, this project plans to select Beijing as the district to study the influence of ice-nucleating microorganisms on haze formation with the methods of classical droplet freezing, high-throughout sequencing, qPCR and so on. The variation characteristics of microbial ice nuclei and their contribution to the atmospheric ice nuclei during the haze period were analyzed, and the structure and abundance of ice-nucleating microbes involved in ice nuclei formation were elucidated. Combined with the physical and chemical properties of atmospheric particulate matter and meteorological parameters, the influencing factors of ice-nucleating microbes in different seasons were discussed. This study will provide a scientific basis for understanding the mechanism of ice-nucleating microbes on haze formation and treatment.

以高浓度颗粒物污染为特征的灰霾，是当今我国大部分城市面临的严重空气污染问题。普遍研究发现微生物是灰霾颗粒物的重要组成部分（10^5 ~ 10^7个/m^3），并发现灰霾会影响微生物丰度、活性和种类，但关于大气微生物的功能及其对灰霾形成的影响目前缺乏报道。根据申请人前期研究发现，相比清洁天，灰霾期冰核菌属丰度增加。考虑到其可作为大气云凝结核和冰核的功能，本项目拟选取北京作为研究区域，利用经典的小滴冷冻法、qPCR、高通量测序等技术，研究大气冰核微生物对灰霾形成的影响机制。分析灰霾形成过程中微生物冰核的变化特征及其对灰霾期大气冰核的贡献，阐明参与冰核形成的冰核菌群落结构和丰度。结合大气颗粒物的理化特性和气象参数，探讨不同季节灰霾期冰核微生物的影响因素。本研究将为深入了解冰核微生物对灰霾形成影响机理和灰霾治理提供科学依据。

空气颗粒物是我国大部分城市空气污染的首要污染物之一。除化学组分外，颗粒物中还存在丰富多样性的微生物，且已有研究发现部分空气微生物可以作为云凝结核和冰核的功能。但是，关于冰核微生物是否会影响空气颗粒物的生成尚不清楚。所以本研究探索了冰核微生物对灰霾（颗粒物）形成的影响。研究发现，城市空气中不乏冰核微生物的存在，其丰度高达4.52%。主要冰核细菌有六种，Psychrobacter，Pseudomonas，Brevibacterium，Lysinibacillus，Xanthomonas，和Pantoea。主要冰核真菌有三种，Fusarium，Mortierella，和Cryptococcus。一般冰核细菌丰度高于冰核真菌，而且冰核细菌在粗颗粒中丰度高于细颗粒，冰核真菌则相反。空气中冰核微生物对不同浓度的空气颗粒物污染响应不同。轻污染期间其浓度与空气污染物浓度正相关，而重污染（灰霾）期间，其浓度与空气污染成负相关。另外，冰核细菌和真菌的响应也不同，低污染天细颗粒中冰核细菌与空气污染成正比，而冰核真菌无显著关系。所以，冰核微生物对空气颗粒物的贡献可能主要在轻污染时期。而且研究发现，冰核微生物还受气候条件（相对湿度、气压等）和其他微生物的影响。特别地，冰核真菌Cryptococcus主要受其他真菌的负调控，而Fusarium主要受正调控。本研究对于系统认识空气中冰核微生物对灰霾的影响提供数据支撑。本项目发表论文4篇，其中SCI 3篇。