Seasonal Changes Of Harmful Chemical Components In PM_2.5 And Population Health Risk Assessment In Haikou And Changzhi

ObjectivesThis study analyzed exposure levels of polycyclic aromatic hydrocarbons（PAHs）and heavy metals in PM_2.5during sampling in haikou and changzhi cities.The characteristics,sources of pollution and the health risks to people of polycyclic aromatic hydrocarbons（PAHs）and heavy metal elements in PM_2.5in Haikou and Changzhi,which have different air pollution conditions,were detected,so as to provide scientific basis for the prevention and control of air pollution and protection the health of residents for Haikou City,and Changzhi City.MethodsSampling points were set up in Haikou City and Changzhi City respectively.The PM_2.5in the air was collected by using the Commodore PM_2.5sampler,and samples were taken 24 hours a day for one consecutive month in each season.PAHs were analyzed by gas chromatography-mass spectrometry（GC-MS）,and heavy metal elements were analyzed by inductively coupled plasma mass spectrometer（ICP-MS）.The characteristic ratio method,enrichment factor method and principal component analysis method were used to analyze the sources of pollutants,and the health risk model proposed by the USEPA as a framework combining with Monte Carlo simulation were used to assess the Incremental lifetime cancer risk of pollutants to different populations.Research results1.The median exposure concentration ofΣPAHs in PM_2.5in Haikou was4.988ng/m³and 23.274ng/m³in Changzhi.The difference in the exposure concentrations ofΣPAHs in the two cities was statistically significant（P<0.05）,and Changzhi was higher than that in Haikou;the exposure concentration ofΣPAHs had obvious seasonal changes,which were winter>spring and autumn>summer in Changzhi.2.The differences in the exposure concentrations of Pb,Cu,Zn,Mn,Cd and Cr in PM_2.5in Haikou and Changzhi were statistically significant（P<0.05）,the heavy metal concentration in Changzhi was higher than that in Haikou.The concentrations of Pb,Cd,Mn and Ni in both cities did not exceed the annual average limits set by China or the WHO（Cu,Zn and Cr didn’t have annual average limits）,the exposure concentrations of Pb,Cu,Zn,Mn and Cd in the two cities were generally highest in winter and lowest in summer.3.The main pollution sources of PAHs in PM_2.5in Haikou were motor vehicle emission sources,followed by other fossil fuel combustion（mainly natural gas,small amount of coal combustion）and biomass combustion;the main sources of pollutants in Changzhi were coal combustion sources,followed by motor vehicle emissions,biomass combustion,and petroleum sources.Among them,the coal combustion ratio in Changzhi in winter was greater than that in summer.4.The main pollution sources of heavy metal elements in PM_2.5in Haikou were vehicle emissions,natural sources（dust,rock weathering,etc.）and a small amount of coal etc;the main sources in changzhi city were coal combustion and motor vehicle emissions,and a small number of natural sources（dust,rock weathering,etc.）,among them,the coal combustion ratio in Changzhi in winter was greater than that in summer.5.The Incremental lifetime cancer risk of PAHs in PM_2.5in Haikou and Changzhi for different populations were shown as adult male>adult female>children.The ILCR of the population in Haikou City was lower than 10^-6specified by the USEPA,and in Changzhi City was between 10^-6and 10^-4.6.The carcinogenic heavy metals Cd and Ni in Haikou and Changzhi had ILCR to children,adult males and adult females of less than 10^-6,and ILCR of Cr for children,adult males,and adult women is between 10^-6and 10^-4.The ILCR of the three carcinogenic heavy metals to the population were adult males>adult females>children,and the ILCR of Cd and Cr to children,adult males,and adult females were all higher in Changzhi City than in Haikou City.7.The non-carcinogenic risk hazard quotients of the 7 heavy metals in the PM_2.5of Haikou and Changzhi to the population were Mn>Cr>Pb>Cd>Zn>Cu>Ni,and the hazard quotients were less than 1.Conclusion1.The pollution level of harmful chemical components in PM_2.5in Haikou City was low,and there was no obvious seasonal change inΣPAHs,the pollution levels of seven heavy metals were higher in winter than in summer except Cr;the pollution levels of harmful chemical components in PM_2.5in Changzhi were higher than those in haikou city,ΣPAHs and heavy metals（except Cr and Ni）were higher in winter than in summer.2.The main sources of harmful chemical components in PM_2.5in Haikou were motor vehicle emissions,natural sources and other fossil fuel combustion（mainly natural gas,small amount of coal combustion）,while the main sources in Changzhi were coal combustion and motor vehicle emissions.3.The carcinogenic risk of PAHs in PM_2.5to the population was considered negligible in Haikou,while had potential carcinogenic risk in Changzhi.The carcinogenic risk of Cd and Ni to people in the two cities were negligible carcinogenic risks,and the carcinogenic risk of Cr was a potential carcinogenic risk.Non-carcinogenic risks of heavy metals in PM_2.5to people in the two cities were negligible non-carcinogenic risks.