Concentration Analysis And Physical And Chemical Property Study Of Fine Particulate Matter In Changchun Metro

With the rapid increase in urban population and the rapid development of China’s metro system,making more and more people choose the metro to travel,the air quality inside metro stations will also affect the health of passengers and staff,so the study of air quality in metro stations is particularly important.The objectives of this study are to analyse and interpret the concentration levels,spatial and temporal distribution characteristics of particulate matter inside and outside Changchun metro stations,to analyse the physicochemical properties of PM2.5 in the environment at the platform ends and outside the stations,and to summarise the corresponding causes by comparing the variability of the physicochemical properties of PM2.5 in different areas in order to solve the pollution problems in the stations.We calculated the chemical elements in PM2.5 on the metro workers’exposure dose and the results were used to assess the health of the workers.In this paper,we monitored particulate matter（PM）concentration levels at four metro stations in Changchun,China.We monitored long-term particulate matter concentrations at the city government stations from September 2019-December 2019,and from September 2020-December 2020,where PM2.5 concentrations on station platforms,halls,waiting areas and outside the stations ranged from 82-184μg/m³,67-190μg/m³,95-192μg/m³and 7-267μg/m³,with platform,station halls,and waiting area areas had daily average PM2.5 concentrations of over 100μg/m3,indicating that particulate matter pollution is more serious in Changchun underground stations in winter.We used statistical analysis SPSS and Stata software to perform correlation analysis,data fitting and linear regression analysis on the particulate matter concentration data in the station environment with humidity,temperature and CO₂concentration data to derive the degree of influence between each environmental parameter and particulate matter concentration.In our study,we found that the train piston effect has an impact on the particulate matter concentration in the station,and that the particulate matter concentration in different areas of the station varies cyclically with the frequency of train operation.During the study of the physicochemical properties of particulate matter.We used inductively coupled plasma optical emission spectroscopy（ICP-OES）to determine the content of 13 metal elements in PM2.5 in Changchun metro stations,and found that the concentrations of Fe,Cu and Cr in PM2.5 at the end of the station platform were higher than those in the area outside the station,with the following trends in the concentrations of the 13 elements:Ca>Fe>Al>Mg>Na>K>Cr>Zn>Ni>Mn>Cu>The morphological structure of PM2.5 in the station and off-site environment was observed using a scanning electron microscope and an energy spectrum analyser to compare and determine the differences in the morphological structure of the particulate matter in the two areas,where the individual particles of PM2.5 outside the station were predominantly spherical and lumpy,and the individual particles of PM2.5 at the end of the station were predominantly flaky and flocculent.To determine the human health effects of the metal elements in PM2.5,risk values for the average daily dose（ADD）from three routes（ingestion,inhalation and dermal exposure）were calculated according to Chinese population exposure parameters for assessing the health of metro workers,including four heavy metal elements（Cd,Cr,Pb,Ni）identified as carcinogenic risk elements and eight metal elements（Mg,Mn,Cr,Ni,Cu,Zn,Cd,Pb）were identified as non-carcinogenic risk elements.The results showed that the non-carcinogenic risk values for chromium and nickel elements were higher in the metro station platform environment than outside the station environment,and the non-carcinogenic risk values were higher for female staff working in the metro for long periods than for men.Therefore,indoor air quality in metro stations has affected the health of metro workers,so it is necessary for the metro to develop strategies to ensure the health of its staff.