| In recent years,the prevention and control of air pollution in Weihai has improved a lot and the air quality become better obviously.However,affected by special climate and pollution transport,especially the pollution emission in Winter heating period and the dust in Spring,there is still sir pollution and the PM2.5concentration of fine particles in polluted days increased significantly.Carrying out monitoring analysis and source analysis of fine particles is very important for Weihai City to formulate targeted PM2.5 pollution control measures and to improve the status of PM2.5 air pollution.For specifying the component features and source of winter and spring fine particles of Weihai,this research analyzes the PM2.5 concentration data of Weihai in2017 and 2018,concluding the variation characteristics of PM2.5 air pollution.According to the biggest PM2.5 pollution sources and regions of Weihai,the Branch School of Shandong University,Lingang woodworking machinery and Wendeng Bureau of Landscape are selected as the monitoring points.From January to March2018,sampling intermittently for 50 days and 300 PM2.5 samples of fine particles of Weihai were obtained.Then weighted the samples and carried out elemental carbon/organic carbon analysis,metal element analysis and water-soluble ion analysis,screening out the characteristic components with high ion concentration from the samples of each monitoring station.In the meantime,the characteristics and contribution proportion of PM2.5 components in polluted days and clean days during the sampling period were compared,and the three pollution processes during the sampling period were selected for comparative analysis.Through literature review and PM2.5 chemical composition spectrum was established through field investigation of pollution sources,and PMF receptor model was used to analyze the sources of fine particles in Weihai City.The main research results are as follows:?1?From 2015 to 2018,the average PM2.5 concentration of Weihai was31.24?g/m3,and 63 days were excessive pollution,which showed that PM2.5 had been the main air pollutant of Weihai in recent years.The PM2.5 concentration changed with seasons greatly.There were more pollution in heating period and in spring.The concentration of PM2.5 was higher in winter,reaching 41.76?g/m3,and slightly lower in spring,and the same in summer and autumn.The daily variation of PM2.5 had no obvious regularity,and the hourly average concentration was about 31.13?g/m3.The annual trend of PM2.5 showed a"single peak"trend,and PM2.5 reached the maximum concentration of 46.18?g/m3in December.?2?During the sampling period,the spatial distribution of PM2.5 mass concentration had not obvious difference.The concentration of Shandong University was higher than that of Lingang,and the variation range of mass concentration was34.063 to 35.946?g/m3.In the same time,the mass concentration of organic carbon?OC?was higher than that of element carbon?EC?.The mass concentration range of OC was 2.975 to 4.183?g/m3,and the mass concentration range of EC was 1.299 to1.681?g/m3.Wendeng Bureau of Landscape was located in the suburb,and there was more biomass burning and bulk coal burning during the heating period,resulting in higher carbon component concentration at this point,while the Shandong University was located in the downtown,so there was less carbon emission.The range of mass concentration of water soluble ions was:NO3-?7.3358.321??g/m3,NH4+?5.1076.183??g/m3,SO42-?4.4354.731??g/m3,Na+?0.2130.305??g/m3,Ca2+?0.5480.767??g/m3,Cl-?0.6300.873??g/m3,K+?0.2280.307??g/m3and Mg2+?0.1410.190??g/m3.The point of Wendeng Bureau of Landscape was affected by coal burning during heating period,agricultural source emission and secondary transformation,so the mass concentration of secondary ion,K+and Cl-ion was relatively high;the Shandong University was close to the sea,and greatly effected by sea salt particles,and there was construction dust nearly,resulting in high mass concentration of Na+,Ca2+and Mg2+ions.Among the components of metal elements,the change range of mass concentration of metal elements which took up a larger proportion was:Si?0.3730.658??g/m3,Al?0.2630.425??g/m3,Fe?0.4530.547??g/m3,Zn?0.1300.185??g/m3,Cu?0.0400.049??g/m3,Pb?0.0250.043??g/m3.The mass concentration of Si and Al was higher in Shandong University due to the coal-fired emission of thermal power plant and dust nearby;the mass concentration of Fe was higher in Lingang due to the emission of surrounding industrial enterprises.?3?The total concentration of NH4+,NO3-and SO42-in PM2.5 was 62.42?g/m3 in polluted days,and 14.78?g/m3 in clean days,which is obviously increased.The NO3-in heating period was mainly from regional transport,and the main source of ammonium aerosol was mainly from transport and local contribution.The concentration of water-soluble ions in polluted days was higher than that in clean days,and the water-soluble ions in PM2.5 in clean days took more proportion than that in polluted days.The sea salt ions changed more.The proportion of Na+in clean days was 11.14%,while that in polluted days was 3.48%,and the proportion of Mg2+in clean days was 0.62%,while that in polluted days was 0.24%.The Na+and Mg2+were mainly from clean weather groups at sea,and the pollution weather groups were mainly from inland,so the proportion of Na+and Mg2+in PM2.5 of clean days was relatively high.?4?During sampling period,there were three typical polluting process,among which the PM2.5 concentration of Haze1 was 50.10±35.69?g/m3,while that of Haze2was 74.80±9.09?g/m3 and that of Haze3 was 100.77±15.55?g/m3.It's concluded by analyzing the fine particles components in three polluting process:The concentration of Cl-in Haze1 was?1.13±0.86??g/m3,which accounted for 2.26%of the total.The mass concentration of K+is?0.73±0.52??g/m3,which accounted for 1.46%.K+was the characteristic factor of biomass combustion and Cl-was the characteristic factor of combustion source.The pollution process of Haze1 was greatly affected by the emission of burning source.The proportion of K+in Haze2 was smaller than that in the other two pollution processes,and it was less affected by burning emissions.The concentration of secondary inorganic ions in Haze3 was higher than that in the other two pollution processes.The concentrations of NO3-,NH4+,SO42-were?31.27±5.09?,?20.74±2.48?,?13.94±1.94??g/m3,respectively.The regional transport characteristics of nitrate and sulfate showed that the pollution process was affected by regional transport,while Ca2+concentration was significantly increased,which was?1.11±0.20??g/m3,indicating that the pollution process was affected by soil and dust.The K+mass concentration?0.60±0.24??g/m3 increased comparing with Haze3,indicating that Haze3 was also affected by burning source emissions.?5?Analyze the PM2.5 industry source with PMF model and the result showed that:the most component in air PM2.5 of Weihai was secondary aerosol pollution source?32.436%?,and next were mobile sources?15.6-18.9%?,coal sources?12.1-17.8%?,biomass combustion sources?9.0-10.4%?and dust sources?8.6-11.3%?respectively.That took up less proportion were process source?2.1-8.3%?,non road moving source?2.4-3.7%?and sea salt?3.5-5.6%?respectively.Therefore,the secondary inorganic aerosols,mobile sources,coal-fired sources and biomass combustion sources which accounted for a large proportion of emissions should be focused on and controlled.Some suggestions should be put forward,such as strengthening the air pollution control in winter heating period,fostering the emission control on mobile sources,enhancing the elaborate control on dust in construction sites and residue transport vehicles,and improving the construction of air pollution monitoring network. |
PDF Full Text Request