| In recent decades,due to the acceleration of urbanization and industrialization in China,the problem of urban environmental pollution has increased significantly.Polycyclic aromatic hydrocarbons（PAHs）are one of the most common organic pollutants in urban environment,and urban dust fall is an important carrier of PAHs,so it has important indicative significance for the monitoring of PAHs in urban dust fall.Shenyang’s industrial activities are intensive,and PAHs produced by the combustion of fossil fuels are discharged into the environment,affecting the city’s ecological system and human health.Therefore,this study took PAHs in Shenyang urban dust fall as the research object,and analyzed the physical and chemical indexes of Shenyang urban dust fall samples and the content level,composition characteristics and spatial distribution characteristics of PAHs.The sources were analyzed and the ecological and health risks generated by PAHs were evaluated.It provides data support for understanding the pollution status of PAHs in Shenyang’s urban dust fall.The main research results are as follows:（1）Shenyang urban dust fall samples were collected in 2020,and the dust fall was generally weakly alkaline,with a p H average of 8.33.The average organic carbon content of urban dust fall in Shenyang was 2.62%,and the coefficient of variation was 4.20%,and the spatial distribution was not much different.Shenyang urban dust fall accounted for the largest proportion of 10～100μm particle size class,accounting for 39.31%,and the particle size distribution curve showed a single-peak normal distribution.（2）The content of 14 kinds of PAHs in Shenyang urban dust fall was analyzed by high performance liquid chromatography∑PAHs content range from 371.57～3300.04μg/kg,the average value is 1244.76μg/kg,and the content of∑LMW PAHs（low molecular weight PAHs）accounts for 24.57%of∑PAHs content,which is only about one-third of∑HMW PAHs（high molecular weight PAHs）content.The order of∑PAHs content in dust fall in Shenyang functional areas was as follows:commercial area（1848.22μg/kg）>traffic area（1205.25μg/kg）>residential areas（1141.17μg/kg）>park areas（885.94μg/kg）,the content of∑PAHs in dust fall of different particle sizes in Shenyang City showed a trend of increasing with the decrease of particle size.（3）The composition characteristics of PAHs in Shenyang urban dust fall are 4 rings>3 rings>5 rings>2 rings>6 rings,accounting for 51.72%,18.10%,14.08%,9.51%and6.60%of the∑PAHs content,respectively.The spatial distribution characteristics indicate higher levels of∑LMW PAHs in the urban center and north,while∑HMW PAHs in the east are higher.High population density,traffic congestion and frequent economic activities led to the highest average content of PAHs in the first ring road,reaching 3300.04μg/kg.（4）The source analysis of PAHs in urban dust fall in Shenyang was carried out by correlation analysis,eigenratio method,principal component analysis method and positive definite matrix factor analysis method,and the results showed that the sources of PAHs included fossil fuel combustion（25.96%）,Coal combustion（11.86%）,transportation emissions（10.17%）,oil sources（24.81%）and natural gas combustion（27.21%）.（5）Due to the change of industrial activities and energy structure in Shenyang,the content of PAHs in Shenyang’s urban dust reduction decreased significantly.The ecological risks of PAHs were evaluated by Nemero comprehensive index method,toxicity equivalent method and low median effect interval method,and the results showed that the ecological risk of PAHs pollution in urban dust reduction in Shenyang was low.Health risk models show that children are most vulnerable to PAHs compared to adolescents and adults,with hand-mouth intake being the most important route of exposure.The CR values of 43.33%of the sampling points were higher than 10-6,but the CR values of all sampling points were well below the maximum acceptable risk set by the USEPA(10-4). |
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