Chemical Characterization And Source Apportionment Of PM_2.5 In Luoyang,2018

In this study,the atmospheric PM_2.5samples were collected at two sites in different seasons from 2018 to 2019 in Luoyang,and the concentration levels of water-soluble inorganic ions（WSIIs）,inorganic elements,organic carbon（OC）,elemental carbon（EC）and 16 preferentially controlled polycyclic aromatic hydrocarbons in atmospheric fine particles were analyzed and the seasonal variation characteristicsof these component were studied.In addition,a health risk assessment model and positive definite matrix factor model（PMF）were conducted to evaluate the carcinogenic and non-carcinogenic risks of toxic elements and polycyclic aromatic hydrocarbons and the source of PM_2.5,respectively.The trajectory and potential source contribution factor method were also used to study transmission path and potential sources of PM_2.5in Luoyang.The results showed that the average concentrations of PM_2.5at the two sites of Gaoxin and Linxiao were77±38 and 83±39μg·m^-3,respectively,with the seasonal mean level following the order:winter>spring>autumn>summer.The proportion of WSII in PM_2.5is 55.1%with 54.2%respectively;NO₃^-,SO₄^2-,NH₄⁺as the main accounting for 88.1%and 87.7%of WSIIs at Gaoxin and Linxiao sites,and with good correlations.NO₃^-,SO₄^2-,NH₄⁺mainly existed in the form of NH₄Cl,（NH₄）₂SO₄,NH₄NO₃.S,Cl,K,Al,Si,Fe,Ca,Mg,and Na,were the main elements in PM_2.5accounting for more than 93%of the 27 total element mass concentrations,The annual average concentrations of OC and EC were 12.4±7.7 and 1.2±0.5μg·m^-3,accounting for 16.2%and 1.6%of PM_2.5respectively at Gaoxin site;the annual mean values of OC and EC at Linxiao site were 13.4±7.7 and 1.3±0.5μg·m^-3,accounting for 16.1%and 1.6%of PM_2.5respectively.Coal combustion,traffic sources and biomass combustion were the main sources of carbonaceous particulate matter by using the ratio of OC/EC in Luoyang.The average total concentration of 16 PAHs was 36.05 ng·m^-3and 39.33 ng·m^-3at Gaoxin and Linxiao sites,respectively,with the seasonal variation of winter>autumn>spring>summer.The results of diagnostic ratios showed that the main sources of PM_2.5-bound PAHs were motor vehicles,coal combustion and biomass burning.The chemical mass balance of PM_2.5showed that the two sites of Gaoxin Linxiao were dominated by crustal materials,secondary inorganic ions,and organic matter,and there were obvious seasonal changes;The proportion of crustal materials in spring is higher than other seasons（Gaoxin 35.4%,Gaoxin 35.8%）,and SNA accounts for a significant proportion of PM_2.5in summer,autumn and winter.There are obvious non-carcinogenic risks of toxic elements in the skin exposure route of children and ingestion exposure;in general,the carcinogenic risks of toxic elements was within the acceptable level.Polycyclic aromatic hydrocarbons existed carcinogenic risks ingestion and dermal,and the non-carcinogenic risks showed the order of ingestion exposure>inhalation exposure>dermal ingestion.PMF results indicated that for Gaoxin and Linxiao sites the secondary aerosol sources contributed（41.16%and 40.44%）;coal-fired sources（24.49%and 24.9%）;motor vehicles（17.07%and 16.43%）;dust sources（10.41%and 11.41%）;industrial sources（6.87%and 6.82%）.were the main sources of PM_2.5.In addition,PM_2.5concentrations in the ambient air in Luoyang was mainly affected by the airflow in the northwest and northeast in spring,autumn and winter,while the external air mass was mainly transported in the east in summer.