Source Apportionment And Preliminary Study On Cytotoxicity Of PM_2.5 In Jiaxing From 2016 To 2017

Atmospheric particulate matter was a general term for various solid and liquid particulate matter present in the atmosphere.PM_2.5（aerodynamic diameter≤2.5μm）,which was also known as fine particulate matter,received widespread attention because of its harmful effects.In this study,we conducted multi-site,long-term sampling of Jiaxing City,as well as comprehensive component analysis and dual-model source analysis,and based on the results,proposed targeted recommendations for the prevention and control of PM_2.5 in Jiaxing City.Through oxidative stress on cells exposed to PM_2.5 and NMR-based metabolomics analysis,PM_2.5-induced cytotoxic key metabolic markers and their associated cellular oxidative damage pathway mechanisms were discovered.The details are as follows:（1）From October 2016 to November 2017,PM_2.5 samples were collected at 5 sites in Jiaxing.Scanning electron microscopy（SEM）and transmission electron microscope（TEM）showed that soot aggregates and coal-fired fly ash were generally the most abundant components in PM_2.5samples.All PM_2.5 samples were analyzed gravimetrically for mass concentrations and then determined for various compositions.Our results showed that the concentrations of PM_2.5 in 5 sites were in accordance with the rules of winter>spring>autumn>summer.The concentration of components in winter plus spring was higher than that in autumn plus summer with the exception of trace elements.Carbonaceous species and water soluble inorganic ions were the most abundant components of the total PM_2.5 mass concentrations at 5 sites,accounting for 26.17–50.44%and 34.27%–49.6%,respectively.The high SOC/OC ratio indicated that the secondary organic pollution in Jiaxing was severe.The average ratios of NO₃^-/SO₄^2-ranging from 1.006 to 1.246 in 5 sites indicated that mobile sources contributed more to the formation of PM_2.5 than stationary sources in Jiaxing.The ratio of BeP/（BeP+BaP）（range 0.52 to 0.71）in samples reflected the impacts from outside region transportation of Jiaxing.According to PMF and CMB model analysis,emission list,PM_2.5concentration-time series,wind speed,NO₃^-/SO₄^2-ratio,secondary inorganic ion mass ratio,etc.,after comprehensive evaluation,Jiaxing comprehensive source analysis results are obtained.External transportation accounted for 21–41%,and local sources contributed 59–79%.Among the local source contributions,coal combustion（23%）,fugitive dust（8%）,industrial production（26%）,mobile sources（30%）,others（13%）.This result is basically equivalent to the analysis results of the neighboring urban sources around the Yangtze River Delta.（2）The PM_2.5 induced cytotoxicity showed that a decrease in cell viability as well as an increase of the levels of extracellular lactate dehydrogenase（LDH）release in time-and concentration-dependent manner.Increased intracellular ROS levels and reduced?ψm in concentration-dependent manner after 48 h of PM_2.5 exposure were also found.The metabolites in PM_2.5-treated A549 cells were examined via nuclear magnetic resonance（NMR）-based metabolic approach to clarify the molecular mechanism of PM_2.5-induced toxicity.NMR analysis revealed that 23 metabolites were significantly altered in PM_2.5-treated A549 cells,including up-regulation of PE,Lactate,Succinate,Creatine,3-hydroxybutyrate,Acetate,Isoleucine,Phenylalanine,Histidine,Tyrosine and decreased levels of Inosine,Hypoxanthine,Xanthine,Uridine,Cytidine,PC,PE,GPC,Choline,α-glucose,β-glucose,Nicotinamide,Glutamine,Glutamate.Metabolic pathway analysis showed that PM_2.5could interfere with choline phospholipid metabolism,energy metabolism,amino acid metabolism and nucleotide metabolism in A549 cells.In short,PM_2.5 pollution in Jiaxing during the winter and spring season,was more severe than that in summer and autumn.Secondary pollution is the most important source.Therefore,attention should be paid to increasing the source control and supervision of gaseous precursors related to industry and motor vehicles,and combining local prevention and regional prevention.In addition,PM_2.5 induces cytotoxicity and triggers cellular oxidative stress.Metabolomics analysis indicates that several important metabolic pathways are involved in cellular biooxidation.