| As a kind of persistent organic pollutants,polycyclic aromatic hydrocarbons（PAHs）are carcinogenic,teratogenic,and mutagenic,that can be transformed into substituted polycyclic aromatic hydrocarbons（SPAHs）with stronger toxicity under chemical or microbial action.Therefore,the pollution characteristics and behaviors of PAHs and their derivatives in the environment have attracted much attention.As the Yangtze River is an important link in China’s economic development,the water environment is related to the lasting and stable development of the regional economy,but we still lack an in-depth understanding of the pollution characteristics and sources of PAHs and SPAHs in different media of the Yangtze River.In this study,19 PAHs and 15 SPAHs（including 6 methyl-substituted PAHs（MPAHs）,5 nitro-substituted PAHs（NPAHs）,and 4 oxidized PAHs（OPAHs））were analyzed in suspended particulate matter（SPM）during the dry,wet and normal periods and surface sediments in the Yangtze River during the dry period,respectively.Moreover,the health and ecological risks of PAHs and SPAHs were assessed along the Yangtze River.The results showed that the concentrations of∑19PAHs and∑15SPAHs in the SPM of the Yangtze River ranged from 0.37 to 204.62μg·g-1and 0.05 to 29.82μg·g-1,with mean concentrations of 19.56μg·g-1and 3.57μg·g-1.The mean concentrations of∑OPAHs and∑MPAHs were 6.40μg·g-1and 4.31μg·g-1,but NPAHs were not detected in the SPM during the sampling periods.The concentrations of∑19PAHs and∑15SPAHs in the Yangtze River sediments ranged from 47.99 to 500.39 ng·g-1and 5.07 to 81.72 ng·g-1,with the mean concentrations of 257.33 ng·g-1and 35.88ng·g-1;and the mean concentrations of∑MPAHs,∑OPAHs,and∑NPAHs were17.1 ng·g-1,16.0 ng·g-1and 2.8 ng·g-1,respectively.Significant spatio-temporal distribution characteristics of PAHs concentrations were observed in the SPM and sediment along the Yangtze River.The concentration of PAHs was increased with the decreasing distance to the Three Gorges Dam.However,the interception effect of the dam led to a decreased sand transport and suspended solid concentration to downstream,resulting in a sudden decreased PAHs concentration downstream of the dam.High population density,industrial activities and more developed shipping in the middle-lower reaches resulted that the PAHs concentration was increased with the decreasing distance to the estuary of the Yangtze River.The seasonal variation pattern of∑（S）PAHs concentration in SPM of the Yangtze River was as the order:dry period>normal period>wet period.The methods of molecular ratio and principal component analysis was used to identify the sources of PAHs and SPAHs.The results of source identification suggested that the PAHs in SPM mainly originated from the combustion of biomass,fossil fuels,and liquid fuels,and the PAHs in sediments originated from oil and biomass combustion,coal combustion,and oil spills.SPAHs in the SPM and sediment mainly originated from combustion sources and photochemical transformation.The toxicity equivalent factor method was used to evaluate the health risk of PAHs in suspended solid and sediment in the Yangtze River.The results showed that the health risk caused by PAHs in suspended solid was medium risk level,and the high risk caused by PAHs in suspended solid during the dry period should be taken seriously.Moreover,the health risk caused by PAHs in sediment was at a low level.The risk quotient method to assess the ecological risk of PAHs in SPM showed that more individual PAHs in SPM were at risk in all river sections of the Yangtze River,where the ecological risk level was higher in the dry period,followed by the normal period and wet period.The ecological risk of PAHs in sediments was evaluated by the sediment quality benchmark method and sediment quality standard method,and the results showed that their occurrence was less likely,but the ecological risk of high-cyclic PAHs such as Ba P,DBA,and Bb F,Bk F,Icd P and Bghi P with no specified safety values still needed attention. |
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