| Ambient particulate matter(PM)is one of the main pollutants in urban air.The chemical composition and sources of urban atmospheric PM are complex and greatly affected by environmental factors.In addition,the content of carbon and nitrogen species in the PM is usually higher.Hefei,a typical city in Yangtze River Delta urban agglomeration,was selected as the research area in this thesis to investigate the characteristics,transformation processes,and formation mechanisms of chemical components of atmospheric PM.Moreover,the sources of PM were identified and the control method for a typical pollution source was put forward.These could provide scientific guidance for internal control,external coordination and manual intervention of atmospheric PM pollution in Hefei city and even the Yangtze River Delta region.A total of 140 PM2.5 samples,140 PM10 samples,3 fly ash samples from garbage incineration,4 dust samples,2 soil samples,5 exhaust pipe dust samples of gasoline vehicles,and 5 exhaust pipe dust samples of diesel vehicles were collected from Hefei.In addition,a Polyvinyl chloride(PVC)sample was also collected.These samples were analyzed using Ion Chromatography(IC),Scanning Electron Microscopy(SEM),Energy Dispersive X-ray Spectrometry(EDX),Element Analysis(EA),Isotope Ratio Mass Spectrometry(IRMS),Thermogravimetric analyzer-Fourier Transform Infrared Spectroscopy(TG-FTIR),and Pyrolyzer-Gas Chromatography/Mass Spectrometry(Py-GC/MS).The chemical composition characteristics,influencing factors,sources,migration paths,and transformation processes of atmospheric particulates in Hefei city were systematically studied based on the theoretical knowledge of environmental chemistry,environmental geochemistry,thermochemistry,spectroscopy,mathematical statistics,and model fitting.Furthermore,human health risks were assessed and control studies for typical pollution sources were conducted.The main research findings and results were as follows:(1)Based on the concentration characteristics and chemical composition of PM2.5 and PM10 at different pollution levels in Hefei,it was determined that the concentration and chemical components of PM increased with the aggravation of pollution.In particular,PM2.5 accumulation was more significant,which could be better used to characterize the atmospheric PM pollution in Hefei.Besides,the microstructure analysis revealed that PM2.5 and PM10 mainly existed in the forms of spherical particles and aggregated state.(2)According to the correlation of chemical components in PM2.5,the dominant forms of the secondary inorganic aerosols were(NH4)2SO4 and NH4NO3.In addition,the interaction mechanism between carbon/nitrogen species in PM and gaseous pollutants(NO2,CO,O3)in the atmosphere was revealed.It was observed that carbon and nitrogen species,as well as the stable isotopic composition of carbon and nitrogen were negatively correlated with temperature,positively correlated with relative humidity,and not significantly dependent on wind speed.It’s worth noting that there was no obvious correlation between elemental carbon(EC)and meteorological conditions studied in this thesis.(3)The carbon and nitrogen stable isotopic composition of potential PM2.5 pollution sources were established.Combined with Principal Component Analysis(PCA)and Positive Matrix Factorization(PMF)model analysis,PM2.5 sources in Hefei were accurately identified.According to the analytical results of PMF,the contributions of the main PM2.5 sources were determined and shown in descending order:combustion/waste incineration and/or industrial emission(42.06%)>secondary aerosols(24.04%)>vehicle exhaust(23.57%)>re-suspended dust(10.33%),which was consistent with PCA and stable isotopic composition.Furthermore,it was demonstrated that PM2.5 primarily originated from long/medium-distance transportation during the two serious pollution events in the entire campaign based on the cluster analysis of 72 h air mass backward trajectory using Hybrid Single Particle Lagrangian Integrated Trajectory(HYSPLIT-5)model.(4)PVC from municipal solid waste,a typical pollution source of PM2.5 in Hefei,was selected as the research object.The control method for the typical pollution source of atmospheric PM was proposed using pyrolysis and gasification technology.Simultaneously,the release behavior of volatiles during rapid pyrolysis of PVC was investigated using TG-FTIR and Py-GC/MS.The relative contents of main volatiles at different final pyrolysis temperatures decreased in the following order:aromatics(76.79-81.81%)>alkenes(2.86-7.19%)>HCl(3.02-3.10%)>chlorinated hydrocarbons(0-0.46%).In addition,the formation mechanisms of main volatiles from PVC rapid pyrolysis were elucidated based on free-radical reactions.(5)The relative risk(RR)and attributable proportion(AP)of lower respiratory tract infection(LRI),chronic obstructive pulmonary disease(COPD),lung cancer(LC),ischemic heart disease(IHD),and stroke caused by the long-term exposure to PM2.5 of Hefei in 2019 were evaluated using an integrated exposure response(IER)model.The results showed that the RR and AP of LRI,COPD,and LC were constant for different age groups,while those of IHD and stroke decreased with increasing age.Moreover,premature deaths caused by the five diseases in different age groups and gender were compared.It was observed that premature deaths increased with age in all age groups except those aged 60-65.Additionally,premature deaths for males were found to be significantly higher than those for females in all age groups except those over 80 years old. |
