| Along with the rapid urbanization,Shanghai has showed unprecedentedly grow in population.meanwhile,the consumption of resources coupled with the emission of pollutants have caused serious of environmental pollution problems,which hindered the sustainable development of society,economy and environmental.Polycyclic aromatic hydrocarbons(PAHs)are a kind of persistent organic pollutants,with strong carcinogenic,teratogenic and mutagenic effects.they are widespread in the environment and able to long distance migration,Which has significant potential harm to the environment and ecology.This study systematically explored spatial-temporal distribution,stmospheric and ecological risk of PAHs by collecting lake sediment from public parks in Shanghai;analyzed the influence of urban LUCC on the occurrence of PAHs in surface sediments,inorder to explore the impact of urbanization parameters on PAHs contents and provide scientific data for pollution control.Thirty-two surface sediment samples were collected from 32 parks lakes in four different urbanized areas of Shanghai,including the central urban core area(CUC,inside the inner-ring highway),the development urban area(DDU,between the inner-and middle-ring highway),the developing urban area(DIU,between the middle-and outer-ring highway),and the suburban area(SU,outside the outer-ring highway).Three sediment cores were collected from Luxun Park in Hongkou District,Fuxing park and xingjiangwan Park in yangpu District,respectively.The distribution of polycyclic aromatic hydrocarbons(PAHs)in the surface sediments of Shanghai Park lakes were significantly difference.The mean concentrations of ?16PAHs was 1133ng/g,which range from 55.75 ng/g to 4927.66ng/g,significant differences between were distinguished in sediment from different urbanized areas which were manifested in the process of gradual decline from the core urban area to the suburbs areas.The hotspots(sample sites with high concentration of?16PAHs)existed in the urban areas with large traffic volume,old industrial areas in the west side of Huangpu River,and emerging industrial areas in the suburbs areas.The 4 ring PAHs concentration was highest at each sampling point and the concentration of 3 rings,4 rings,5 rings and 6 rings in the core area were higher than that of other regions,the suburbs was lowest.The concentration of TEQ in the surface sediments range from 3.42ng/g to 751.23ng/g.The concentrations of toxicant concentration in four urbanization areas were shown that the core urban area(CUC)>developed urban area(CUC)DDU)>developing city(DIU)>suburb(SU),the highest concentration appears in the central city of Lu Xun Park(S1)with 751.23ng/g.The risk assessment based on risk quotient(RQ)shows that the single Flu has a high ecological risk,the ecological risk of PAHs in the central urban area was the highest,the suburb was at a low ecological risk level,and the developed urban and developing urban areas were moderate ecological risk grade.There will continue to exacerbate the ecological risks in sediments,With the high degree of urbanization and industrialization of continuous input of anthropogenic sources.The LUR model revealed the significant contribution of traffic congestion index and numbers of industrial points to PAHs.The adjusted R2 of the LUR model constructed with ?16PAHs??2ringPAHs??3ringPAHs??4ringPAHs??5ringPAHs and?6ringPAHs as the dependent variable were 0.984?0.529?0.979?0.977?0.974 and 0.943,respectively.There were significant correlation between the simulated concentration of PAHs and the measured concentrations(p<0.01)in three LUR models,and the correlation coefficients were 0.7660.679?0.728?0.702?0.715 and 0.761,respectively.RMSE were 0.362?0.342?0.317?0.447?0.410 and 0.423,respectively.The results show that the model can simulate the spatial distribution of PAHs.Three sediment cores recored the pollution patterns of PAHs in urban environment of Shanghai in 1761-2012,1861-2012 and 1779-2012 respectively.The fluxes of 16 PAHs and 7 strong carcinogenic PAH in the three sediment exhibited fluctuant increases since 1900s and accelerated after the establishment of People's Republic of China in 1949 and the implementation of reform and opening up policy in 1978.The focusing-corrected mean sedimentation fluxes of ?16PAHs(strong carcinogenic ?7PAHs)were 159.93(93.26),109.64(65.53),280.45(159.51)ng/cm2/yr,respectively.The flux ratio of ?16PAHs(strong carcinogenic ?7PAHs)in the three sedimentary cores after 2000 was 162.74(194.62),98.82(98.95),356.78(394.57),respectively.That further confirming that PAHs suffered large anthropogenic influence.The significant increase of PAHs in the C3 sediment core May be related to its own geographical features and the surrounding environment.PMF to analyzed the source of PAHs in sediments and Characteristic ratio sedimentary columns,the results show that the sources of PAHs are similar,mainly from pyrolysis sources,which are mainly fossil fuels and biomass combustion.The analysis of the correlation between urbanization parameters and PAHs deposition showed that the formation and evolution of the pollution pattern of PAHs in Shanghai urban parks were closely related to urban population agglomeration,economic development level,energy consumption and industrial structure.The STIRPAT model quantitatively analyzed the contribution of urbanization parameters to PAHs deposition,the results show that the total population,the proportion of heavy industry and the coal consumption are the main factors of PAHs deposition.The three indexes increase by 1%and the PAH flux increases by 0.172%-0.198%,0.314%-0.358%and 0.297-0.308%,respectively.Path analysis results also shown that the the direct and indirect effects of total population,heavy industry ratio and coal consumption on the PAHs deposition were significant. |
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