Preliminary Study On Physic-chemical Characteristics And Sources Of Fine Particles In Early Spring Of Zhangjiakou City

Particulate matter pollution has aroused worldwide concern recently.Atmospheric particulate matter not only has influenced air quality and human health,but also has impacts on global climate change.Beijing-Tianjin-Hebei is one of the areas with the most serious PM2.5 pollution in China.However,due to the special location and climate characteristics,the air quality of Zhangjiakou City has a large difference with other cities.The air quality of Zhangjiakou is better,but easy to affected by dust weather.In this study,a single particle aerosol mass spectrometer(SPAMS)was employed to analyze the physical and chemical characteristics,mixing states,aging conditions and sources of atmospheric single particles during the period of early spring(from February to March)of 2016 in Zhangjiakou City.The author analyzed and compared the characteristics of atmospheric particles between the haze and clean days,the dust event and periods before the dust event,respectively.It is helpful to understand the characteristics of fine particles in Zhangjiakou City from various aspects,it can provide datas for the work of air pollutional prevention and control in Beijing-Tianjin-Hebei regions.Specific work and related research results are presented as follows,(1)Component characteristics of fine particle in haze and clean days during early Spring of 2016 in ZhangjiakouSPAMS was used for on-line monitoring,then analyzed the characteristics of particles in haze(H1)and clean day(C1and C2),and compared the types and mixing states of particles in different weathers.The results showed that the following types of particles were observed : elemental carbon(EC),organic carbon and elemental carbon hybrid particulate(OCEC),organic carbon-levoglucan(OC-Lev),organic carbon-Nitrate/Sulfate(OC-Nitrate/Sulfate),mineral dust,potassium rich(K-rich),sodium and potassium(Na K)and metal(Metal)particles,and nitrogencontaining organic matter(KCN)particle type was only found in clean days.OCEC and OC-Lev particles were the two main categories of the particles during the two weather events,which accounted for over 60% of total particles.During the haze period,the atmospheric particles were mixed with the secondary components,such as nitrate,ammonium and sulfate,indicating a higher degree of aging.During the clean days,the time series of the particles showed a certain regularity,and high peaks which appeared in the Night between 21:00 pm–2:00 am and between 6:00–10: 00 am.During the two weather events,the time series of CN-containing particles,Cl-containing particles,NOx-containing particles and HSO4-containing particles had good consistency and correlation,indicating that these particles might be from the same source or the similar atmospheric process.The results showed that the atmospheric particles in Spring of Zhangjiakou were mainly composed of organic carbon particles,and mainly originated from local coal combustion and biomass burning.During the haze,the particles mainly came from local,surrounding areas of Zhangjiakou and southwest places such as Shanxi,Shijiazhuang;during the clean days,the atmospheric particles were mainly from the local biomass burning and traffic emissions,and then generated by the clean air from the north to dilute.(2)The physical and chemical characteristics and variations of fine particle during a dust event in March of 2016 in ZhangjiakouIn order to explore the emission sources and characteristics of particles during dust event from the aspect of single particles,this study selected a short dust process,i.e.,14:00:00,March 31,2016–24:00:00,March 31,2016,the chemical composition,size distributions and sources of fine particles during a dust event and the period before dust in the early spring of 2016 in Zhangjiakou were analyzed.The results of trace iron method showed the particles during dust event contained both dust-and non-dust particles,which accounted for 12.9% and 87.1% of total particle number.The particle size of dust-particles were greater than non-dust one according to the data from SPAMS.Dust-particles included four major subtypes: Dust-Al,Dust-Si,Dust-metal,and Dust-Ca particles.Each subtype of particles accounted for more than 20% of total number of dust particles,and with the significant characteristics of mineral particles.Non-dust particles included four subtypes: carbonaceous,K-rich,industrial metal and other particles.The ratio of NO3-/HSO4-(particle numbers)was 1.31 in Dust particles,indicating a high degree of particle aging.On the other hand,a comparative study was conducted between the dust and the period before dust(9:00:00,March 30 to 2016-5:00:00,March 31,2016).The particles of the period before dust(DF)were divided into eleven categories: EC particles,OCEC particles,OC particles,Industrialmetal particles,K-rich particles,Na K particles,Dust-Al particles,Dust-Si particles,Dust-Mg particles,Dust-Ca particles and Dust-Ti particles.During the dust event,the content of EC,Industrial metal and Dust particles were increased,while OCEC and OC particles were decreased.Comparing with the period before dust and haze event,the mixing degree of particles and secondary components was higher during the dust event,especially secondary components of the nitrate and ammonium,which indicating that nitrates played a role in the dust event.During the dust event,dust particles of fine particles could mainly originate from the dust sources of Mongolia and Inner Mongolia,and a small part from the mineral and industrial sources of Zhangjiakou and Shanxi.