Ecological Risk Analysis And Source Apportionment Of Polycyclic Aromatic Hydrocarbons (PAHs) In Surface Sediments From Laizhou Bay And Rizhao Offshore Area

The distribution and pollution level of polycyclic aromatic hydrocarbons (PAHs)in the surface sediments from the Laizhou Bay and Rizhao offshore area were investigated and analyzed. Principal component analysis(PCA)were used to analyzed the main sources of PAHs, and providing the theoretical basis for pollution control of PAHs. In this study joint probability curve and overlapping area have been used to analyze ecological risk of individual PAHs in the surface sediments, and mean effects range-median quotient(MERM-Q)and the organiccarbon-normalized were used to analyze the combined ecological risk. So according to the proportion of species affected, the managers could determine protection level, and protecting human health and ecological security. In surface sediments of Laizhou Bay, the total PAH concentration ranged from 23.034 to 327.533ng/g. Except station L02 and station L03, the distribution of PAHs were showed similar patterns in other 15 stations, the PAH distribution were observed a relatively large proportion of low molecular weight, in particular, acenaphthylene, fluoranthene, fluorene, naphthalene, phenanthrene, pyrene were more than 70% of the Total PAHs at each station. The organic carbon content of the sediment varied from 0.41 to 0.90%, with particle size distribution significantly different. There were no correlations between PAHs concentration and physicochemical parameter in sediment samples such as particle size distribution and organic carbon content in Laizhou Bay. The concentrations of PAHs in surface sediments from Rizhao offshore area were in the range of 76.384～27512.023ng/g. Except station R5 and station R12, the distribution of PAHs were showed similar patterns in other 10 stations,the 2～3 ring PAHs were more than 70% of the Total PAHs at each station. The PAH distribution had a relatively large proportion of 4～6 ring compounds at R5 station. The 2～3 ring PAHs were 57.71% of the Total PAHs at R12 station. The organic carbon content of the sediment varied from 0.09～0.79%, with organic carbon content significantly different. Particle size distribution, the organic carbon content of the sediment do not appear to correlate with the PAHs concentrations in Rizhao offshore area. The PCA suggested that PAHs contaminations in surface sediment from Laizhou Bay originated from coal combustion, petroleum combustion, wood combustion and oil spill. Three components accounted for 47.78%, 20.96%and 12.17% of the variability in the data, respectively. The main source of PAHs was identified from petroleum combustion, coal combustion sources and wood combustion and oil spill in Rizhao offshore area. Three components accounted for 62.92%, 17.69% and 8.24% of the variability in the data, respectively. Joint probability curve and overlapping area indicated the acceptable ecological risk of individual PAHs in Laizhou Bay. Among the nine PAHs studied, it found that the overall risk of pyrene was relatively high, with that of acenaphthylene the lowest. For lower exposure levels at which the percentage of species affected was 5% and 10%, the risk associated with chrysene was clearly higher than that of the other eight PAHs. In the surface sediments from Rizhao offshore area, it found that phenanthrene, fluoranthene, pyrene and chrysene showed higher ecological risk using overlapping areas and joint probability, ecological risk of naphthalene, acenaphthene, acenaphthylene, fluorine and anthracene were relatively low. Among the nine PAHs studied, the overall risk of pyrene was the highest, with that of acenaphthylene the lowest. For lower exposure levels, the risk associated with chrysene was clearly higher than that of the other eight PAHs. Except naphthalene, risks of individual PAHs in sediments from Rizhao offshore area were higher than those of their corresponding PAHs in sediments from Laizhou Bay. MERM-Q and the organiccarbon-normalized were employed to analyze ecological risk of PAHs in the surface sediments from Laizhou Bay and Rizhao offshore area. The result showed that ecological risk of all stations in the LaiZhou bay was low. The mean PAH ERM-Qs for all stations none exceeded the value of 0.1, indicating that the potential combined ecological risks of PAHs in surface sediments were generally low. In Rizhao offshore area, the results indicated that the ecological risk of PAHs in surface sediments was relatively higher at R5 station , and the risk was lower in other area. The harm probability was around 50% at R5 station using MERM-Q.