| Due to its smaller particle size,larger specific surface area,stronger adsorption capacity and complex components,fine particles(PM2.5)can enter the circulation system through the respiratory barrier and then spread to the whole body producing adverse health effects,which has become the focus of environmental health risk prevention and control.Therefore,investigating the pollution characteristics and source apportionment of carbon components and polycyclic aromatic hydrocarbons in PM2.5 in different period,then assessing health risk,which can improve prevention and control air pollution pertinently,comprehensively and rationally in Lanzhou.Thus it provide important scientific basis for formulating the plan and management strategy of prevention and control about air pollution risk in the future.This research analyzed the mass concentrations of carbonaceous components and 16priority controls PAHs in heating period,dust,and non-heating and non-dust period in Lanzhou by thermal/optical carbon analyzer?DRI Model 2001A?and gas chromatography-mass spectrometry analyzer?GC/MS?,respectively.On the basis of discussing the formation of secondary organic carbon?SOC?and rings distribution of PAHs,the sources of PM2.5 were analyzed by PMF model and according to 72-h backward/forward trajectories,the potential sources areas and confluence areas were analyzed by Lagrange model,.Finally,the health risks of PAHs to different populations were assessed and some meaningful results were obtained.?1?The carbon components and PAHs pollution levels of PM2.5 in Lanzhou were significantly different in different periods.During the study period,the concentrations of OC,EC and SOC in PM2.5 ranged from 7.82to 27.83?g/m3,2.12 to8.42?g/m3and 3.16t10.58?g/m3,respectively.The concentration of PAHs ranged from 39.61to432.20 ng/m3,in which the proportion of middle and high ring PAHs were higher,and 4-ring PAHs accounted highest with38.68%.In addition,both carbonaceous components and PAHs presented as heating period>dust period>non-heating and non-dust period.?2?The carbon components and PAHs sources of PM2.5 in Lanzhou were different in different periods.The ratios of OC/EC in different periods were between 1.0 and 4.2,indicating that the carbon components in PM2.5 were significantly affected by vehicle exhaust emissions,and it also affected by coal and biomass combustion in the heating and non-heating non-dust periods with contribution of 72.385%and 68.648%respectively,while fugitive dust contributed most to carbon components in the dust period with a contribution of57.478%.Combine with characteristic ratio,PCA and PMF analysis,PAHs mainly came from coal burning and motor vehicle exhaust emissions during heating period and dust period,and their contribution were 61.30%81.16%and 73.11%74.01%,respectively.While vehicle exhaust emissions and natural gas combustion were the main source in the non-heating non-dust period,and its contribution was 56.65%83.61%.?3?The sources of PM2.5 in Lanzhou were basically the same in different periods,while the main contribution sources were not the same.Based on the PMF model,the main sources of PM2.5 were fossil fuel combustion,traffic,industrial,secondary formation and dust in the heating period and dust period.In addition,fossil fuel combustion,industrial and dust contributed higher to PM2.5 in the heating period,which were 26.27%,20.68%and 15.58%,respectively,and the value turned to 22.12%,19.32%and 10.11%in the dust period,respectively.The contribution of traffic and secondary formation contributed higher to PM2.5.5 in the dust period,with24.02%and 16.52%respectively,and the value turned to 23.78%and 12.59%,in the heating period respectively.?4?Based on HYSPLIT analysis,the sources and sinks of PM2.5 in different periods were different in Lanzhou in heating and dust period,the source of PM2.5 was mainly influenced by northwest wind,which brought pollutants along the two flanks of Qilian mountain and then arrived in Lanzhou.While it mainly affected by the Lanzhou surrounding industrial and motor vehicle exhaust emission sources in the non-heating non-dust period.And mainly transmitted to the east and south area of Lanzhou,because of the barrier of Qinling and LiuPanShan,most of them converged to the south-east of Lanzhou.?5?There was no potential health risks for PAHs in PM2.5 in Lanzhou.The carcinogenic and non-carcinogenic risks of PAHs in PM2.5 both fell in acceptable level,with 1.03×10-62.34×10-5 and 2.42×10-51.94×10-3,respectively,and presented as heating period>dust period>non-heating non-dust period,adult male>adult female>children,among which BaP and DahA were the main contributors to the carcinogenic risk,NaP was the main contributor to the non-carcinogenic risk.The loss of life expectancy in adults and children caused by respiratory exposure were 30.97min and13.42min,respectively.Above all,the carbon components and PAHs in PM2.5 in Lanzhou during different periods had high pollution levels,especially in the heating period.The results of source apportionment in different periods were basically the same.The carcinogenic and non-carcinogenic risks of PAHs to human health in PM2.5 were all fell in an acceptable level. |
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