灰霾天气PM2.5单颗粒微物理化学特征演变及相互混合机制研究

The atmospheric fine particulate matter（PM2.5） is one of the principal cause of the haze episodes . Haze episodes (ie. fine particulate matter ) has became an increasingly serious atmospheric environmental issues in China. These fine particulate matters will accumulate during the episode of haze. During the process of accumulation, the physical and chemical properties ,mixing status,optical perporties and human health impact of fine particulate matter will change. This project aims to address aspects of the variation of characterization of microphysical and chemical and mixing status of urban atmospheric fine particulate matter during the haze episodes. The objectives of this study are: 1) collect the PM2.5 samples during the different time of the episode of haze in Zhengzhou, the north-south transition zone; 2) investigate the micro-morphology characteristic of individual particle, size distribution, chemical component, and mixing status by means of high resolution transmission electron microscopy, field emission scanning electron microscopy, ion chromatogram, Inductively coupled plasma spectrometry, and proton induced X ray fluorescence. The major emphasis of this study will be the microphysical and chemical characterizations of different type's fine atmospheric particulate matter with different size, and their variation with different period during haze episode. The transformation phenomena and the mechanism of heterogeneous phase chemical reaction and mixing status during the episode of haze will be revealed. The aims of this project are to appraise the sources and varitions of microphysical and chemical characterizations,mixing and heterogeneous phase chemical reaction, as well as their influencing factors ,of fine atmospheric particulate matter of Zhengzhou during the episode of haze and to provide some theoretical basis for controlling the fine atmospheric particulate matter.

大气细颗粒物的存在是引起灰霾现象的主要原因之一，灰霾天气暨大气细颗粒物污染已成为一个日益严重的大气环境问题。细颗粒物在灰霾天气寿命周期内的累积过程中，会发生物理化学性质、相互混合状态和光学性质及对人体健康影响等的变化。本项目以位于南北过渡地带的郑州市为研究对象，在发生灰霾污染的不同时段,采集PM2.5样品，采用高分辨率透射电镜、场发射扫描电镜、离子色谱、电感耦合等离子质谱和质子诱导X射线荧光技术分析灰霾期间及发生干湿沉降时大气细颗粒物单颗粒的形貌特征、粒度分布、化学成分与混合状态。分析灰霾污染期间大气环境中不同粒径范围不同类型气溶胶颗粒的理化特性、相互混合状态及不同累积阶段的变化规律，揭示灰霾期间气溶胶单颗粒在大气环境中发生的变化规律与非均相化学反应及混合的机理，探讨中原地区灰霾期间大气细颗粒物的来源与微物理化学性质及相互混合状态变化及影响因素，为细颗粒物的污染控制提供重要理论依据。

灰霾天气暨大气细颗粒物污染已成为一个日益严重的大气环境问题。本项目分析了2014-2017年郑州市大气污染特征及变化规律，并以郑州市为研究对象，采用高分辨率透射电镜（TEM）、扫描电镜（SEM）、离子色谱等手段，分析了发生灰霾污染的不同时段大气细颗粒物单颗粒的形貌特征、化学成分与混合状态。大气污染物浓度分析结果表明，2014-2017年郑州市大气污染物以大气颗粒物（特别是PM2.5）为主，浓度有所下降，SO2逐渐降低，但臭氧和NO2污染逐渐增加。郑州市PM10、PM2.5平均浓度冬季最高，夏季最低。相对湿度增加时，颗粒物会吸湿长大，颗粒物浓度（特别是细颗粒物PM2.5）随之浓度增加；降水会使大气污染物浓度下降，降雨比降雪更容易造成颗粒物浓度的下降；霾污染的出现会使大气污染物（除了O3）浓度有较大的上升。郑州O3日逐时变化为典型的单峰型，最大值晴天最高，出现霾时，O3最高值较低; O3浓度一般为夏＞春＞秋＞冬。.SEM和TEM的单个颗粒物的形貌特征及能谱特征分析结果表明：郑州大气PM2.5主要包括烟尘集合体、矿物颗粒、飞灰、有机颗粒、二次生成颗粒等类型，研究表明郑州大气PM2.5主要来自汽车尾气、燃煤、工业生产、各种扬尘（土壤、道路和建筑工地），PM2.5在霾污染发展过程中矿物发生较多的硫化现象，产生了可溶性盐，反映了较严重的SO2污染。利用FESEM-EDS的面扫描技术（mapping）分析的郑州市严重霾污染时大气颗粒物中的元素分布情况,可以看出颗粒物中含有的Al、Ca、S、Si、K、Mg、Na呈现的内部混合状态。.离子色谱分析结果表明：随着灰霾天气的延续，细颗粒物污染的累积，郑州市PM2.5中水溶性离子在细颗粒物中所占比例逐渐增大，SO42-、NO3-和NH4+的浓度占颗粒物水溶性无机离子总浓度的82.7%，郑州市灰霾天气期间PM2.5细颗粒物中的水溶性离子主要是NH4+、SO42-、NO3-，表明代表人为活动排放的二次污染物是PM2.5中主要的贡献成分；NO3-/SO42-的比率均值为1.215，表明PM2.5受到了交通污染的严重影响；NH4+浓度普遍较高，大部分样品中有K+的存在，说明郑州市大气细颗粒物污染受周边农村农业生产影响严重。与其他城市相比，郑州市灰霾天气时PM2.5中水溶性无机离子的污染情况与天津、北京等北方城市的污染情况类似。