| With the rapid development of economic and urbanization,particulate matter has become one of the major atmospheric pollutants in Nanjing.Atmospheric aerosols,especially fine particles(PM2.5,i.e.,particles with an aerodynamic diameter of 2.5μm or less),are harmful to human health and have serious effects on visibility and global climate change.Therefore,understanding of particles as well as physical and chemical characteristics of fine particulate matter has important significance for in-depth understanding particulate pollution.It is of great significance to identify contributions from major sources so that policy makers can develop regional emissions control strategies and design efficient government measures.The research area is focused on Nanjing,through multi-sites long-term continuous observation and kinds of modeling methods to study characteristics of atmospheric particles,spatial and temporal change features and source apportionment.Size-fractionated source profiles for Nanjing were established.Then,this work also explored on-line source apportionment method by combination of regional air quality model RegAEMS and receptor model(CMB model)The main results were shown as follows:First,based on analysis of particulate samples and receptor model(CMB model),characteristics of chemical compositions and source contributions were studied for different functional areas in Nanjing.Characteristics of chemical composition of observational data for size-fractionated particulate matter at Gulou site and Pukou site in Nanjing from May 2010 to April 2011 were analyzed.And the characteristics of the chemical composition of observation data for PM2.5 at Caochangmen(CCM)and Guchenghu(GCH)in Nanjing at 2011.8,2011.11,2012.1,2012.3,respectively and atmospheric PM emissions samples were analyzed.Results indicate that concentrations of PM10 ranged from 37.1μg/m3 to 376.0μg/m3,PM2.5 ranged from 26.4μg/m3 to 212.7μg/m3.The concentrations were much higher than those of European and American countries,but samilar to other cities in China.Particulate matter shows high concentrations during winter and spring in Nanjing,but low concentrations during summer.The main chemical compositions in atmospheric particles are secondary inorganic aerosols and carbom components.Major components in PM2.5 are primary organic matter(POM,24.85%),nitrate(NO3-,18.73%),sulphate(SO42-,18.27%),ammonium(NH4+,9.90%),element carbon(EC,5.61%).Source profiles of size-fractionated particles are established including coal combustion dust,smelting dust,vehicle exhaust,construction dust and soil dust.The results of source apportionment show that construction dust(22.9%),secondary aerosols(22.9%),coal combustion dust(21.6%)and smelting dust(11.3%)were the main sources to PM10.Construction dust has more influence on downtown than suburbs.The major sources of PM2.5 were coal combustion dust(2.2%-39.5%),secondary aerosols(44.2%-65.1%)and vehicles exhaust(6.48%-16.49%).The contribution of coal combustion dust in industrial area is significantly greater than the coontribution of the urban area.Secondly,based on analysis of particulate samples and receptor model,we did research on source contribution to size-fractionated particles during major events with pollution control measures.Size-fractionated particles from July to September were collected continuously using a 9-size interval ambient cascade impactor at an urban site in Nanjing,during the periods in Asian Youth Games(AYG)in 2013 and Youth Olympic Games(YOG)in 2014,respectively.The results indicate that during the AYG,concentrations of PM10,PM2.1,PM1.1 were 90.4 μg m-3,40.4μg m-3,27.0μg m-3 and during the YOG,concentrations of PM10,PM2.1,PM1.1 were 77.4μg m-3,39.7 μg m-3,21.9 μg m-3.The mass concentrations of YOG were lower than those during AYG,especially the concentrations of PM10 were reduced by 16.8%.The main chemical compositions were carbonaceous(27.0%～34.2%),soluble ions(21.6%～25.1%)and crustal elements(15.4%～19.1%)in turn during the AYG,and main chemical compositions were carbonaceous(35.6%～39.5%),soluble ions(27.7%～33.3%)and crustal elements(8.8%～10.6%)in turn during the YOG.The crustal elements decreased significantly during the YOG.The source apportionment shows that the emission from coal combustion(25.9%),vehicle exhaust(10.8%),smelting dust(9.9%)and construction dust(3.9%)are the most abundance sources during YOG.The source apportionment shows that the emission from coal combustion(24.3%),vehicle exhaust(12.8%),smelting dust(10.7%)and construction dust(9.4%)are the most abundance sources during AYG.The contribution of construction reduced obviously,suggesting that the mitigation measurements of controlling the particles worked efficiently in Nanjing.Thirdly,based on the numerical model and receptor model,an on-line Particulate matter source apportionment method for pollution weather is established and be used to ensure quality of the weather during events.with the combination of regional air quality model RegAEMS and receptor model(CMB model)an on-line source apportionment method is established,and was used to calculate contribution of different sources to particle concentration.Take YOG in nanjing city as an example to review the forecast and research PM2.5 source contribution.The source contribution results of model simulations of Nanjing are secondary nitrate(24.6%),coal(21.8%),iron and steel smelting(15.8%),salt(12.7%),vehicle exhaust(9.0%),construction dust(5.9%),secondary sulfate(5.5%)during the YOG.And the results were compared with the results of aerosol mass spectrometer.We found that the two methods both reflected that during the Youth Olympic Games are coal combustion dust and steel smelting dust and their contributions are basically identical.Based on the numerical model and receptor model,source contributions of coal combustion dust and steel smelting dust during YOG(21.6%,15.3%)are less than them before(21.9%、15.7%)and after(22.2%、18.2%)YOG.Source contribution of construction dust(5.2%)is less than it before(5.5%)and after(5.4%)YOG.All of the results show the effect of control work to coal-fired power plant and industry during YOG.Finally,based on backward air path analysis and numerical model,research was focused on the contribution to fine particles from outside Nanjing.Using backward airflow path analysis and backward analysis qualitative and semi-quantitative analysis of Nanjing urban area particulate matter pollution are mainly transported from outarea.With Hysplit model,backward trajectory was used to analyze transmission characteristics of different air masses.Results indicate that in winter and autumn,air masses mainly come from north.In summer,air masses mainly come from south.In spring,air masses come mostly from local area.The concentrations of PM2.5 are affected mainly by local air masses and northern air masses.Using the LPDM model to calculate potential source contribution of PM2.5 in Nanjing.Simulation results show that external transport contribution of PM2.5 is 41.0%for the whole year,the transmission characteristics of PM2.5 for each season(spring,summer,autumn,winter)in external potential delivery were 40.0%,34.0%,40.1%and 49.8%respectively.Through four aspects of research above,this study showed a comprehensive analysis on the characteristics of source contributions to atmospheric particulate matter in different functional areas in four seasons in Nanjing.The source profiles of size-fractionated particles in Nanjing were established.Combining numerical model and receptor model,a new online source apportionment method was established,and was verified with a case study during the Youth Olympic Games.This dissertation provides scientific foundation for controlling atmospheric particulate pollution in Nanjing. |
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