| Polycyclic aromatic hydrocarbons（PAHs）are widely distributed and have a long retention time in the environment that are not easily to decomposed.Entering the human body through the inhalation route,they cause cardiovascular and lung diseases,and also cause mutation of genetic information,which has a great impact on human life and development.Due to the influence of geographical topography,meteorological factors,energy structure,the air pollution is prominent in Baoding city.Therefore,identifying the pollution characteristics of PAHs of typical scenarios in Baoding city and exploring their sources and health risks are essential to take precise measures for preventing and control air pollution and health risk.In this study,we collected gas-phase and particle-phase PAHs samples from seven typical exposure scenarios during the heating and non-heating periods.The mass concentrations of 16 priority control PAHs were analyzed and deter mined by gas chromatography-mass spectrometry（GC-MS）to explore their pollution characteristics.The sources types and potential areas of PAHs in the air of typical scenarios were analyzed.Health risk assessment and life expectancy loss estimation of PAHs for different population groups were carried out,and some meaningful results were obtained:（1）There is some heterogeneity in the pollution levels and distribution characteristics of air PM2.5 and PAHs in typical exposure scenarios in Baoding.The 24 h mass concentrations of PM2.5 in typical exposure scenarios were 90.16μg/m~3-194.78μg/m~3 and 48.06μg/m~3-88.28μg/m~3 in heating and non-heating periods,respectively.Except for the commercial area in heating period,all scenarios exceeded the secondary standard limit of Ambient air quality standards（GB 3095-2012）（75μg/m~3）,and there were significant differences among different exposure scenarios.The concentrations of 16 PAHs were 389.69 ng/m~3-727.14 ng/m~3 and36.22 ng/m~3-52.12 ng/m~3,respectively.The concentration of Phe is the highest in PAHs in all exposure scenarios,and the number of rings was mainly 3-4 rings.2-3rings PAHs mainly exist in the gas phase,4-6 rings PAHs mainly exist in in the particle phase,and PAHs tend to be more in gas phase.（2）PAHs in typical exposure scenarios are affected by meteorological factors,especially temperature,there is no significant difference between different scenarios.In addition to the significant positive correlation with atmospheric pressure,PAHs were significantly negatively correlated with temperature,humidity and wind speed,and the correlation between gas-particle phases and temperature was stronger.The distribution of PAHs between gas and particle phases showed similar patterns with temperature.That is to say,PAHs tends to exist in the gas phase with the increase of temperature.The correlation between 4 rings PAHs and temperature was higher than that between 2-3 rings and temperature,5-6 rings and temperature,and there was no significant difference between different scenarios.（3）The PAHs pollution of typical exposure scenarios has the same source but also has certain differences.The main sources of PAHs in different typical scenarios during heating and non-heating periods are combustion,volatilization and petroleum.The main contribution of PAHs is combustion source in heating period,while the emission of motor vehicle is dominant in non-heating period.In heating period,PAHs in residential areas mainly came from combustion sources while other scenes were mixed sources of traffic and combustion.In addition,there are oil and combustion mixed sources and oil sources.PAHs in all scenarios mainly comes from transportation and combustion mixed source,oil and combustion mixed source,traffic sources and oil sources in non-heating period.（4）There are significant indigenous differences in air mass trajectories and potential source areas in different periods of Baoding.During heating period,the airflow trajectory mainly comes from northeast while non-heating period is mainly from the southeast,south and southwest.The main contribution source areas included Langfang,Cangzhou and Tianjin,central Inner Mongolia and southern Mongolia in heating period.The main contribution source areas were Shanxi,Shaanxi,Shandong,eastern and southern Hebei,Henan and Anhui in non-heating period.（5）The health risks and loss of life expectancy of PAHs in typical exposure scenarios were different in Baoding.The carcinogenic and non-carcinogenic risks and loss of life expectancy of PAHs in typical scenarios were higher in the heating period than those in the non-heating period.The health risks and loss of life expectancy of adult males were higher than females,and decreased in the order of 6-8 years old,9-11 years old,15-17 years old and 12-14 years old children.The non-carcinogenic risk of PAHs was less than 1,and there was no potential non-carcinogenic risk to the population in all scenarios.The total carcinogenic risk of PAHs in all scenarios ranged from 10-6 to 10-4 during heating period,indicating that there was a certain carcinogenic risk,but the risk was acceptable.The carcinogenic risk of PAHs in non-heating period could be ignored.In summary,PM2.5 and PAHs pollution in typical scenarios of Baoding during the heating period was more serious than those during non-heating period.The monomer Phe pollution was higher than other PAHs,and the number of rings was mainly 3-4rings.The main sources of PAHs were traffic and combustion mixed sources,while the main source of PAHs in residential areas during heating period was combustion source.The carcinogenic and non-carcinogenic risks of air PAHs in typical exposure scenarios were higher in the heating period than in the non-heating period,and the health risk of adult males were higher than those of females and children.All scenarios had acceptable carcinogenic risk in the heating period,and their risks could be ignored,but they would cause a certain degree of life expectancy loss.It is urgent to formulate reasonable and effective pollution control and population protection measures to reduce the health risks of PAHs. |
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