Contents Of Polycyclic Aromatic Hydrocarbons In Leaves Of Common Greening Tree Species In Nanjing And Their Relationship With Leaf Characteristics

Polycyclic Aromatic Hydrocarbons(PAHs),as typical persistent organic pollutants,have hydrophobic,liposoluble,carcinogenic,genes mutating and biological accumulating characteristics,which are potentially harmful to biological growth.In recent years,with the rapid development of the city,organic matter pyrolysis and incomplete combustion of fossil fuels in industrial production and transportation,resulting in air content of PAHs in the environment is increasing.The solution of urban PAHs is of great concern to the community.Urban plants can passively monitor and reduce airborne pollutants and play an important role in the removal of atmospheric PAHs.The urban greening tree species is an important part of urban plants,and its leaves can accumulate polycyclic aromatic hydrocarbons in the atmosphere through gas diffusion,dry / wet sedimentation to reduce the pollution of PAHs.In this paper,GC-MS method was used to analyze the content of PAHs in urban greening trees’ leaves,and the ability of absorbing PAHs were compared between 16 trees’ leaves.Six urban trees’ leaves were selected to analyze the correlation between the content of leaves’ PAHs and special leaf area,stomatal density and the wax content.The content of PAHs in leaves of different functional zones were compared,and the reason of spatial differences was analyzed by parse the sources of PAHs.To screen out the species with strong accumulation of PAHs,and better assist the smooth development of PAHs pollution prevention and control work.The results of this study show that:(1)The total content of PAHs in different tree species showed obvious differences.Among the16 trees,the total content of PAHs of camphor’s was the lowest,which was 223.54 ug/kg;the total content of PAHs of Cedar leaves was the highest,which was 15176.73 ug/kg.The total content of PAHs in leaves of evergreen coniferous trees was much higher than that of evergreen broad-leaved trees,evergreen broad-leaved shrubs and deciduous broad-leaved trees.The PAHs in the leaves of16 species were dominated by low ring and tetracyclic PAHs,and the total content of low ring and tetracyclic PAHs accounted for more than 70%.Moreover,the content of PAHs in leaves of 16 species was different.The contents of tricyclic,tetracyclic,pentacyclic and hexacyclic PAHs in Platycladus orientalis,Cypress,Cedar,Platanus orientalis and Poplar were significantly higher than those of other species(P <0.05).(2)There was a certain relationship between leaves characteristics and the content of PAHs in leaves.There was significantly positive correlation(P<0.01)between the total content of PAHs and the wax content,and negative correlation(P<0.05)between the total content of PAHs and the specific leaf area.There was positively correlation(P <0.05)between the content of Pyr and the leaf wax content and stomatal density.There was very significant positive correlation between thecontent of B(b)F and the specific leaf area(P < 0.05).(3)The content of PAHs in different functional zones showed obvious spatial difference.The trend of total polycyclic aromatic hydrocarbon content was: industrial zone> traffic zone>education transportation mixed zone> educational zone> control zone.The composition of the main PAHs in different functional zones is different.The main components of PAHs in educational zone and education transportation mixed zone are the same as the control zone,which was naphthalene,pyrene,phenanthrene,anthracene and fluoranthene.The main components of the transportation zone are pyrene,phenanthrene,anthracene,fluoranthene and indene(1,2,3-c,d)pyrene.The main components of the industrial zone are pyrene,phenanthrene,fluoranthene,benzo(a)pyrene and benzo(a)anthracene.