Health Risk And Ecological Risk Analysis Of PAHs And PCBs From Liaohe Estuarine Wetland Soils

PAHs and PCBs are widespread in soils and tend to be strongly adsorbed to soil.They have adverse health effects on human and environment. Therefore, studies onhealth risk and ecological risk analysis of PAHs and PCBs in estuarine wetland soilswould be very informative. The concentrations of16PAHs, dioxin-like PCBs(DL-PCBs) and atropisomeric PCBs in Liaohe estuarine wetland soil were analyzedby GC-FID and GC-ECD, respectively. The distribution of PAHs and PCBs was alsoinvestigated in the paper. Based on four-step rule of health risk assessment putforward by NAS, multimedia/multipathway exposure model made by US EPA wasadopted to evaluate the health risk of PAHs and PCBs to people exposed. Jointprobability curve and overlapping area were used to analyze ecological risk ofindividual PAHs, and Nemerow composite index was used to assess the combinedecological risk. Quality evaluation criterions，potential ecological risk index and toxicequivalency factors (TEF) were used to analyze ecological risk of PCBs. The resultsacquired in this study would offer scientific evidences for the bioremediation andmanagement of wetland.In Liaohe estuarine wetland soils, the total PAHs concentrations were in therange of0.510×10~3~1.94×10~3g/kg with an average of887g/kg in May2009,and in the range of0.293×10~3~1.74×10~3g/kg with a mean value of675g/kg inAugust2009. The observed PAHs levels were in the moderate range of the globallevels. PAHs were predominated by three-ring and four-ring compounds, whichcontributed58%to the total PAHs, while the concentrations of six-ring PAHs werethe lowest, which only contributed below10%.Total PCBs congeners concentrations ranged from5.15g/kg to12.4g/kgamong all the sites, with a mean value of7.79g/kg in May2009, and ranged from4.03g/kg to11.0g/kg with a mean value of6.14g/kg in August2009. Theobserved PCBs levels met the soil quality standard. The concentrations of PCBs in Liaohe estuarine wetland soil were at a medium level compared with other areasaround the world.In order to investigate potential health risk to human bodies caused by PAHs andPCBs in Liaohe estuaine wetland soil, a preliminary assessment of the health riskcaused by ingestion, inhalation exposure and dermal contact for workers, children andadults was performed by using a health risk method of US EPA. The results showedthat HI values for95%UCL concentrations and maximum concentrations of PAHsand PCBs were far below1under both exposure scenarios, indicating thenon-carcinogenic health risk of PAHs and PCBs was negligible. Moreover, all ofcarcinogenic risk brought by PAHs and PCBs contamination under the two exposurescenarios was lower than10-4, which was in the range of acceptable risk. These resultsindicated that PAHs and PCBs in the soils of Liaohe estuarine wetland didn’t posepotential health risk to children, adults and workers. Among the three groups, childrenwere more easily affected by PAHs and PCBs than adults and workers, for they mayingest more soil in their daily life.Two probabilistic risk approaches and the the Nemerow’s synthetical pollutionindex were adopted to characterize ecological risks of PAHs from Liaohe estuarinewetland soils. Joint probability curve and overlapping area indicated the acceptableecological risk of individual PAHs in Liaohe estuarine wetland. The overall risk ofBaP, Fla, Fle, NaP, Phe was relatively high, with that of Pyr, Ant, Ace relatively low.For lower exposure levels at which the percentage of species affected was5%, the riskassociated with BaP was the highest, followed by Pyr, Fla, and that of Ace the lowest.Nemerow’s synthetical pollution index showed that Liaohe estuaine wetland soil hadbeen polluted slightly by PAHs. However, it should be noted that sites LH26, LH27,LH28reached the level of moderate and heavy pollution.The evaluation results of quality evaluation criterions showed that the totalpotential risk of PCBs from Liaohe estuarine wetland soils was relatively low, whichwill not produce side effects to organism. The results of potential ecological risk indexshowed that the ecological risk of PCBs was relatively higher in sites LH29, LH30,LH31, LH37in May2009and sites LH30, LH31in August2009, and of the rest target sites belonged to the light ecological hazard in different seasons. Moreover,PCBs in the soils of the study area might pose little potential ecological risk based onthe assessment result of TEF.