我国北方冬季灰霾主要有机单颗粒类型及耐热性  

Morphology and heat resistance of the major organic particles in winter hazes of northern China

作　　者：林秋寒 陈姝芮 屠征波 张剑 刘磊 李卫军 LIN Qiuhan;CHEN Shurui;TU Zhengbo;ZHANG Jian;LIU Lei;LI Weijun(School of Earth Sciences,Zhejiang University,Hangzhou 310027,Zhejiang,China;Shandong Academy for Environmental Planning,Jinan 250000,Shandong,China;Hangzhou Academy of Eco-environmental Science,Hangzhou 310000,Zhejiang,China)

机构地区：[1]浙江大学地球科学学院,浙江杭州310027 [2]山东省生态环境规划研究院,山东济南250000 [3]杭州市生态环境科学研究院,浙江杭州310000

出　　处：《地球化学》2022年第2期243-250,共8页Geochimica

基　　金：国家自然科学基金项目(42107108);浙江省自然科学基金项目(LZ19D050001)联合资助。

摘　　要：我国北方冬季气溶胶中有机物所占比重大,对其气候效应、人体健康及大气环境影响进行评估是大气化学研究的热点问题。为了探究冬季灰霾主要有机单颗粒类型及耐热性,本研究利用透射电镜发现北方冬季灰霾中一次有机颗粒较为普遍,根据内混颗粒物的化学组分差异将其分为三种:有机物–矿物颗粒(3%)、有机物–烟尘颗粒(16%)和有机物–二次无机盐颗粒(81%)。此外,本研究还使用管式炉对采集的大气单颗粒样品进行高温加热,再利用透射电镜对加热后的几类典型有机单颗粒形貌和组分特征进行原位跟踪分析。结果显示,近圆形一次有机物经过300℃和500℃加热过程之后,形貌特征无明显变化,表明该类一次有机颗粒具有耐高温特性;半透明穹顶状有机物在300℃下粒径增大且颜色更加透明,表明在此温度下该类颗粒中大部分有机组分能够挥发;将具有有机包裹层的颗粒物在室温及300℃下的形貌特征对比测量,发现虽然二次有机包裹层留有部分痕迹,但是大部分已挥发,进一步升温至500℃时,半透明穹顶状的有机物和有机包裹层在高温过程中挥发完毕。本研究证明北方冬季燃煤排放的圆形一次有机物含有大量的难挥发耐热有机组分,外场观测和实验室分析应考虑此类一次有机颗粒的耐高温特性,从而更准确地对我国北方冬季大气有机物进行定量和溯源分析。Organic aerosols account for a large proportion of fine particulate matter during winter in northern China. The atmospheric organic aerosols significantly impact climate change and human health, which is a hot topic in atmospheric chemistry. This study explored the morphology and heat resistance of the major organic particles in winter hazes by transmission electron microscopy(TEM) and found that primary organic particles were common in winter hazes of northern China. According to the composition and morphology of the internally mixed organic particles, we classified them into three major types: organic matter-mineral(3%), organic matter-soot(16%), and organic matter-secondary inorganic aerosol(81%). Moreover, we used a tube furnace to heat the samples at high temperatures and then used TEM to track the morphology and composition of several typical organic particles. Our results show no noticeable change in the morphology of the round organic particles at 300 ℃ and 500 ℃, suggesting that this kind of primary organic particles have high temperature resistance. Individual particle analysis shows the size of dome-like organic particles increased at 300 ℃ and particles became more transparent,suggesting that these organic particles were volatilized. The organic coatings left little residue at 300 ℃, suggesting that most of them were volatilized. When the temperature was further increased to 500 ℃, the dome-like organic particles and organic coatings disappeared on the substrate. Therefore, we can conclude that the primary spherical organic particles contain heat-resistant organic components. Field observation and laboratory analysis need to consider high temperature resistance of spherical organic particles in winter hazes to precisely quantify and trace the atmospheric organic components in northern China in winter.

关 键 词：灰霾 有机气溶胶 单颗粒分析 形貌特征 耐热性 

分 类 号：X513[环境科学与工程—环境工程]