【作者】 王辉；

【导师】 韩金保； 韩斌；

【作者基本信息】 河北大学 ， 电子信息硕士（专业学位）， 2024， 硕士

【摘要】 PM_2.5是指空气动力学直径小于或等于2.5μm的大气颗粒物,它可以通过吸收和散射太阳辐射影响气候,也会对人类健康产生危害。华北平原是中国大气PM_2.5污染最严重的区域之一,漯河市地处华北平原腹地,在秋冬季经常观察到数天到数周的PM_2.5严重污染事件。因此,有必要对漯河市大气PM_2.5的污染特征及来源进行研究。有机气溶胶（Organic aerosol,OA）是PM_2.5的重要组成部分,但目前由于其组成复杂且国内相关监测仪器较少,加上已有仪器时间分辨率有限,致使人们对其污染特征及来源的认识有限。基于此,本研究以漯河市为研究对象,于2022年9月-12月期间在漯河市颗粒物成分观测站使用高分辨率飞行时间气溶胶化学组分质谱仪（Time of Flight Aerosol Chemical Speciation Monitor,TOF-ACSM）对大气PM_2.5及其组分进行在线观测,结合气象数据和气态污染物数据,分析漯河市PM_2.5及其组分的污染变化特征以及主要影响因素;采用正矩阵因子分解模型（Positive Matrix Factorization,PMF）对PM_2.5中有机气溶胶进行来源解析;探讨供暖活动对PM_2.5及其组分浓度的影响;最后对观测期间发生的重污染天气事件进行具体分析。了解漯河市秋冬季污染特征,从而为漯河市及其他典型轻工业城市的大气污染研究提供数据。论文的主要结果如下:观测期间,低风速高湿度和高O₃的大气环境为污染创造了条件。PM_2.5平均浓度为56.0μg/m³,其化学组分中,硝酸盐和有机物是主要贡献者,占比分别为36.3%和31.0%,其次是铵盐（12.9%）、硫酸盐（11.9%）、黑碳（5.4%）和氯化物（2.6%）。PMF解析出四个OA因子,分别为氧化有机气溶胶（Oxygenate Organic Aerosol,OOA,44.9%）、生物质燃烧有机气溶胶（Biomass Burning Organic Aerosol,BBOA,31.1%）、交通源排放有机气溶胶（Hydrocarbon Like Organic Aerosol,HOA,14.5%）、燃煤有机气溶胶（Coal Combustion Organic Aerosol,CCOA,9.4%）。一次污染物主要来自本地排放,二次污染物受到来自东北和东南方向的传输影响。无污染时段以有机物为主,在高污染时段以硝酸盐为主,有机组分中,一次有机气溶胶（Primary Organic Aerosol,POA）在随着有机物浓度的升高时贡献呈现整体升高的趋势,而OOA却呈现整体下降的趋势。供暖后PM_2.5质量浓度从60.7μg/m³增加到65.7μg/m³,化学组分中硝酸盐（40%）和有机物（30%）仍是两个主要贡献者,黑碳和氯化物质量浓度出现显著增加,涨幅分别达到93.2%和193.2%。供暖活动导致CCOA增加让POA的贡献从50%增长到59%成为主导。供暖前后的日排放模式以及驱动日变化的因素相对相似。观测期间发生四起污染事件,对四个事件的案例分析突显了严重污染的形成机制因气态污染物排放量和气象条件而存在显着差异。这些事件是由供暖前停滞气象条件下高O₃浓度促进光化学生成或较高O₃和高湿度共同促进光化学及液相生成以及供暖后高湿度和低风速的大气环境下高水平排放驱动的。更多还原

【Abstract】 PM_2.5refers to atmospheric particulate matter with an aerodynamic diameter less than or equal to 2.5μm,which can affect the climate by absorbing and scattering solar radiation and can also be hazardous to human health.Organic aerosol（OA）is an important component of PM_2.5,which has a complex composition and is poorly known due to the few relevant instruments and limited time-resolved measurements in China.Its composition is complex,and little is known about organic aerosol’s source and formation mechanism due to the lack of relevant instruments and limited time-resolved measurements in China.The North China Plain is one of the most seriously polluted areas in China,and although the annual average PM_2.5concentration in the Beijing-Tianjin-Hebei region decreased from 106μg/m³in 2013 to64μg/m³in 2017,it is still 1.45-1.88 times higher than that in the Yangtze River Delta region.Luohe is in the middle of three major polluted areas,namely the Beijing-Tianjin-Hebei periphery,the Yangtze River Delta,and the Fenwei Plain,and it is a transition area where pollutants are transferred from the north to the south,which,together with the continuous emission of local pollutants,leads to the formation of pollutants and the formation mechanism of organic aerosols.Together with the continuous emission of local pollutants,this leads to a long-time accumulation and residence of pollutants,which triggers persistent heavy pollution,and severe particulate pollution events of several days to weeks are often observed in the fall and winter.In this study,we used a sampling site representative of Luohe City to observe the PM_2.5chemical components online during September-December 2022 using a Time-of-Flight Aerosol Chemical Speciation Monitor（TOF-ACSM）.We used the Positive Matrix Factorization（PMF）model.The PMF model is used to analyze the source of organic aerosols’mass spectral information and understand the composition of organic aerosols in the region.Combined with the observation data from other instruments,we observed,studied,and analyzed the changes in air quality and aerosol components in autumn and winter.By analyzing the changes in the chemical composition of PM_2.5before and after heating,the effect of heating activities on the chemical composition of PM_2.5is investigated.Combining meteorological factors and gaseous pollutants to analyze the heavy pollution events during the observation period to provide data support for the air pollution management in the region and the study of air pollution in typical light industrial cities.The main conclusions are as follows.1 During the observation period,the atmospheric environment with low wind speed,high humidity,and high O₃created conditions for pollution.The average concentration of PM_2.5was 56.0μg/m³,and among its chemical components,nitrate and organics were the main contributors,with 36.3%and 31.0%,respectively,followed by ammonium salts（12.9%）,sulfate（11.9%）,black carbon（5.4%）and chloride（2.6%）.2.PMF resolved four OA factors,which were oxidized organic aerosol（OOA,44.9%）,coal combustion organic aerosol（CCOA,9.4%）,biomass burning organic aerosol（BBOA,31.1%）,and organic aerosol emitted from transportation sources（HOA,14.5%）.3.On clean days(PM_2.5concentration less than 50μg/m³),the two most contributing components were organic（34%）and nitrate（30%）,whereas nitrate（39%）outweighed organic（27%）on polluted days(PM_2.5concentration greater than 200μg/m³),with organic dominating in non-polluted hours and nitrate dominating in highly polluted hours.Among the organic components,POA showed an overall increasing trend in contribution with increasing organic concentration,while OOA showed an overall decreasing trend.4.When domestic heating began,the PM_2.5mass concentration increased from 60.7μg/m3 to 65.7μg/m3,and nitrate（40%）and organic matter（30%）were still the two main contributors among the chemical components.In contrast,the e BC and chloride mass concentrations significantly increased,with a rise of 93.2%and 193.2%,respectively.The increase in CCOA due to heating activities allowed POA to grow from 50%to 59%,overtaking SOA as the dominant.5.Four pollution events occurred during the observation period,and case studies of the four events highlight significant differences in the mechanisms of severe pollution formation depending on gaseous pollutant emissions and meteorological conditions.We observed three main types of haze events driven by photochemical production of high O₃or a combination of photochemical and liquid-phase reactions of higher O₃and high humidity during stagnant meteorological conditions during the NHP as well as localized high levels of emissions at low humidity and wind speed during the HP.更多还原