Source Analysis And Health Risk Assessment Of PM2.5 In Nanchang Subway Stations

To investigate the pollution level,characteristics,sources and contamination of toxic metals（TMs）and health risk on employees attributable to the soluble TMs,atmospheric fine particles（PM2.5）were collected in five stations of the Nanchang subway in central China throughout 2019.PM2.5 was highly variable across sampling sites,subway stations and seasons.PM2.5 contamination was higher in the October holidays,followed by January,May,November,and June.Overall the highest PM2.5 level occurred in station D,followed by stations B,E,A,and C.The analysis indicated that the PM2.5 consists of 23.7%inorganic species,29.6%ions,11.8%carbon compounds,and 34.9%other materials.The most abundant element in the PM2.5 was Fe at a concentration range from 5.3±5.04μg/m3 to 14.97±12.96μg/m³among sampling sites.Other common elements found were Pb,Mn,Co and Cu.Cd,As and Cr（VI）far exceeded the standard recommended in NAAQS.Among anions and carbon compounds,NO₃^-showed the highest concentration with 19.14±23.29μg/m³,followed by SO₄^2-,OC,Cl^-,and EC.The samples all contain secondary organic carbon（SOC）,and the carbon components of platform and ticket office are similar.Source analysis was carried out by principal component analysis（PCA）and positive matrix decomposition（PMF）,among which six sources of samples were obtained by PMF results:wheel/rail system（29.90%）,brake and catenary（4.30%）,vehicle traffic（25.40%）,coal combustion（19.70%）,secondary sources（13.20%）,and industrial emissions（7.50%）.Then High concentrations of PM2.5 with enriched levels of metallic constituents could significantly affect the health and comfort of metro employees.the bioavailability of PM2.5-TMs in platform and ticket counters samples was determined using Gamble’s solution,and the risk to human health of total TMs and bioavailability in PM2.5 was investigated.As,Ba,Co and Pb were found the most bioaccessible,while V,Fe and Cr were the less bioaccesible.Despite the carcinogenic and non-carcinogenic risk associated with the total contents of PM2.5-bound TMs was found to be significant,no significant non-carcnogenic risk was found and only As and Cr（VI）causes considerable carcinogenic risk to subway workers based on the bioaccessible fractions.Potential carcinogenic risk was found to be more severe in platform than that in ticket counter,and As and Cr（VI）were identified as the priority pollutants of health risk.Therefore,to reduce PM2.5 pollution in Nanchang subway,we should consider pollution source control and subway air management to reduce the impact on the health of employees.