基于单颗粒质谱技术的石家庄冬春季气溶胶成分特征及混合状态研究

利用位于石家庄市大气梯度监测站(20 m)的单颗粒气溶胶质谱仪分析了冬、春季大气环境中气溶胶的化学组成及混合状态,并采用ART-2a分类法对气溶胶分类。结果表明,石家庄市大气中主要存在8类颗粒物,即元素碳(EC)、有机碳(OC,相对分子质量小于150)、高分子有机碳(HOC,相对分子质量大于150)、混合碳(元素-有机碳混合,ECOC)、重金属、左旋葡聚糖碎片(LEV)、矿物质和富钾颗粒。8类颗粒中绝大部分包含SO_4~-、NO_2~-和NO_3~-等二次离子组分,表明采集到的颗粒物大都经历了不同的老化,或与二次组分进行了不同程度的混合。冬季气溶胶的主要成分是OC(数浓度36.1%),谱图含有C2H+3、C_2H_3O~+、C_5H_3~+、C_6H_5~+等离子,主要来自化石燃料、生物质等燃烧产生的一次排放颗粒,以及由挥发性有机物光化学氧化而成的二次有机颗粒;春季气溶胶的主要成分是EC(数浓度43.6%)和矿物质(数浓度15.4%)。EC中含有一系列单质碳峰,来自化石燃料或木材等生物质不完全燃烧的一次排放;矿物质颗粒中含有Mg~+、Al~+、Ca~+、Fe~+及SiO_3~-,主要来自扬尘。发生灰霾时,冬季OC和ECOC颗粒占比增大,EC颗粒占比减小;春季矿物质和ECOC颗粒占比变大,OC颗粒占比变小。随着灰霾天气发生,冬、春季碳气溶胶与二次无机气溶胶颗粒的混合加剧,而NH_4~+与碳气溶胶的混合加剧最为明显。冬季气溶胶的数浓度与气象因素的相关性高于春季,而低风速、高湿度和低气压易导致灰霾出现。石家庄市春季和冬季气溶胶污染应分别从机动车尾气、扬尘及燃煤、制药企业加以管控。

Analysis and investigation of the composition features and mixing status of aerosol in Shijiazhuang in winter and spring based on the single particle aerosol mass spectrometer

The paper is inclined to bring about an analysis and investigation of the composition features and the mixing status-insitu of aerosol in Shijiazhuang in winter and spring seasons via a single particle aerosol mass spectrometer (SPAMS) located in the atmospheric gradient monitoring station (20 meters) of the city.For the study purpose,we have collected and done the analysis of the chemical compositions and mixing status of the particle aerosol in the atmospheric environment in winter of 2014 and spring of 2015.What is more,we have identified and categorized the aerosol particles generated by using ART-2a.As a result,we have found that the aerosol particles can be classified into 8 dominant groups,that is,the organic carbon (OC),the elemental carbon (EC),the mixed elemental/organic carbon (ECOC),the high-molecular organic carbon (HOC),the levoglucosan (LEV),minerals,heavy metal and the alkali particles (Na-K).Most of the above mentioned 8 kinds of particles have been found containing secondary ion components,such as SO4-(m/z =-96),NO2-(m/z =-46) and NO3-(m/z =-62),which imply that they have probably been going through different degrees of aging process,or mixed with secondary components.The main components of the winter aerosols have been found consisting of OC (36.1％),while those of spring aerosols have been EC (43.6％) and minerals (15.4％).On the other hand,the spectrum of OC has been found consisting of C2H3+,C2H3O+,C5H3+,C6H5+ with some other organic ions.Specifically speaking,they are mainly made of the first emissions from the burnt fossil fuels and biomasses,etc.as well as the secondary organic particles produced by the photochemical oxidation of volatile organic compounds.Furthermore,the spectrum of EC has been found constituting a series of elemental carbon peak mainly resulting from the emission of incomplete combustion of biomass,such as fossil fuels and woods.The spectra of mineral particles have been discovered containing Mg +,Al +,Ca +,Fe + and SiO3-,which is mostly from the dust.We have also found that the ratio of OC and ECOC particles tends to increase,while the ratio of EC particles tends to decrease in the hazy winter days.Moreover,since the minerals and ECOC particles account for a large proportion,that of OC particles would tend to be smaller in spring.Particularly,in the hazy winter days,the mixing state of carbon aerosol and secondary inorganic aerosol particles are likely to get intensified,with the mixing state of NH4+ and carbon aerosol being intensified most probably.What is more,it is more likely that the numerical concentration of aerosol particles may turn to be more correlated with the changes of the meteorological factors in winter than in spring,such as the low wind speed,higher humidity and lower pressure tend to increase harshly the occurance of haze days.