Chemical Composition And Pb,Sr Isotopes Tracing Of PM_2.5 In Quanzhou

Quanzhou is a coastal city located in south-east of China and is the starting point of the maritime Silk Road in the“the Belt and Road”Initiative.During rapid economic development,its atmospheric environmental problems are becoming increasing concerns.PM_2.5 is a major pollutant in the atmosphere and its harm is widely known.The key to controlling PM_2.5 pollution is accurate understanding of its source.The source of urban atmospheric particles is complicated,based on this characteristic,we carry out the research on the chemical component feature and the source apportionment study,in this case,we can reveal the main sources of PM_2.5,providing the theoretical foundation and scientific basis for the government to conduct the pollution control on the atmospheric particulate.In this paper,PM2.5 samples were collected at five different sites in Quanzhou City from March 2014 to January 2015.Ion-exchange chromatography was used to analyse 9 water-soluble and inorganic ions in PM_2.5,such as Na⁺,NH₄⁺,K⁺,Ca²⁺,Mg²⁺,F^-,Cl^-,NO₃^-,and SO₄^2-.Inductively coupled plasma mass spectrometry（ICP-MS）was used to analyse the trace metal elements and lead isotope components in PM_2.5 and potential pollution sources.Thermal ionization mass spectrometry（TI-MS）was used to analyse the strontium isotope components in PM_2.5 and potential pollution sources.The following research were carried out:1)Spatiotemporal characteristics of atmospheric PM_2.5 mass concentration in Quanzhou City;2)Seasonal distribution characteristics and source apportionment of water-soluble ions;3)Characteristic element identification in potential pollution sources and spatiotemporal distribution characteristics of trace metal elements in PM_2.5;4)Seasonal distribution characteristics and source apportionment of lanthanides in PM_2.5;5)Bioavailability health risk evaluation of toxic metal elements in PM_2.5;5)Tracing of lead and strontium isotopes from PM2.5 pollution sources.The results of the study showed that:（1）The range of atmospheric PM_2.5 mass concentration variation in Quanzhou City was 7.2μg/m³-103.4μg/m³.The overall PM_2.5 mass concentration was lower and showed seasonal variation characteristics of spring>summer>winter>autumn.The PM_2.5 mass concentration in mixed residential and industrial areas was greater than in commercial and residential areas.（2）The water-soluble ions in atmospheric PM2.5 of Quanzhou City showed significant seasonal variation characteristics,the total mass concentration of the 9water-soluble ions in spring and winter were significantly higher than in summer and autumn.SO₄^2-,NO₃^-,and NH₄⁺are the major ions in the water-soluble ions of atmospheric PM_2.5.5 in Quanzhou City.The proportions of these ions out of total water-soluble ions by mass concentration were spring（90.3±3.3）%,summer（68.8±11.7）%,autumn（78.9±7.1）%,and winter（74.0±18.4）%.（NH₄）₂SO₄,NH₄HSO₄,NH₄NO₃ were the main forms by which ammonium salts exist in spring and winter,while ammonium salts mainly exist as NH₄HSO₄ and NH₄NO₃ in summer and autumn.PMF analysis suggested that the water-soluble ions in atmospheric PM_2.5 of Quanzhou city were mainly derived from sea salt,secondary sources（secondary nitrates and secondary sulphates）,construction dust,municipal solid waste incineration and biomass combustion fly ashes.（3）The concentration of trace metal elements in atmospheric PM_2.5 of Quanzhou City showed greater fluctuations during spring and winter while variations in summer and autumn were relatively mild.Inter-station differences in PM2.5 trace metal element concentrations were small.（4）The average lanthanoids concentration in PM_2.5 were 4.242ng/m³（95.863μg/g）.And positive Ce and negatiove Eu were also observed in PM_2.5.The distribution characteristic analysis of lanthanoids in PM_2.5 showed that atmospheric PM_2.5 in Quanzhou City might had originated from:1)Urban dust,including construction dust（dust from road surfaces of construction sites and cement）and soil dust.2)Dust from burning coal,which are mainly fly ashes from coal power stations and industrial coal-fired boilers;3)Vehicular exhaust dust;4)Fly ashes from municipal solid waste incineration.（5）Bioavailability assessment of toxic elements in PM_2.5.5 showed that Ni,As,Cd,Zn,Cu and Pb were bioavailable elements,while Be、Cr、Co、V and Ba were remarked as potential bioavailable elements.The toxic heavy metals in atmospheric PM_2.5 of Quanzhou City mainly entered the human body through inhalation and threatened human health.In the 9 types of toxic heavy metals monitored,Cr,Co,and As had potential carcinogenic risks towards residents in Quanzhou City.Ni and As had potential non-carcinogenic risks.Cr,Co,As,and Ni were key elements for control of atmospheric heavy metal pollution in Quanzhou City from now on.Various environmental agencies and government departments should accelerate the drafting of a list of pollution sources and proposed feasible control measures for key heavy metals to protect human health.（6）The tracing of lead and strontium isotopes of atmospheric PM2.5 pollution sources found that the main primary sources of atmospheric PM_2.5 in Quanzhou City were derived from construction dust,traffic emissions,coal combustion,municipal solid waste incineration,and soil dust.The secondary sources were ammonium sulfate,ammonium bisulfate,and ammonium nitrate.Isotope mixing model predictions found that the contributions of various sources are:Traffic emission（33.4%）>construction dust（22.3%）>secondary sources（18.6%）>coal combustion（14.9%）>soil dust（7.8%）>municipal solid waste incineration fly ash（3.0%）.