Multimedia Fate Modeling And Ecological Risk Assessment Of Polychlorinated Biphenyls In The Littoral Areas Of Bohai Sea And Yellow Sea

Polychlorinated biphenyls(PCBs)are a set of persistent organic pollutants(POPs)which have been widely distributed in the environment.PCBs have attracted great attention in domestic and foreign researches due to their characteristics such as bio-refractory,bioaccumulation,long-distance transport,and biological toxicity.After PCBs enter the environment,they will transfer,diffuse,and transform between different environmental media,affecting human health and ecological environment in different ways.Therefore,it is necessary to study the distribution and fate of PCBs in the multimedia environment.This study took the littoral areas of Bohai Sea and Yellow Sea as the research area.Based on the BETR-Urban-Rural model,concentrations of PCB28,PCB101,and PCB153 in eight environmental compartments(rural air,urban air,rural soil,urban soil,vegetation,fresh water,fresh water sediment,and coastal water)were simulated under the steady-state assumption.Meanwhile,the reliability of model results was assessed through comparison between the measured and simulated concentrations,sensitivity analysis,and uncertainty analysis.Moreover,reserves in multimedia and transfer fluxes of chemicals in the littoral areas of Bohai Sea and Yellow Sea were analyzed according to the model results.Finally,the ecological risk assessment of PCBs in soils and sediments were carried out using environmental quality standard risk method and potential ecological risk index method.According to the estimation results of PCB emissions,the total emissions of PCB28,PCB101,and PCB153 in the littoral areas of Bohai Sea and Yellow Sea in 2013 were710.93 kg,96.71 kg,and 30.39 kg,respectively.Tangshan City was the highest emission area for PCBs.Results showed that PCB concentrations in urban soils,rural soils,and sediments were higher,while PCB concentrations in air and water were lower.The higher concentrations of chemicals in coastal water were mainly distributed near the river estuaries,and the dilution of coastal water caused the concentrations of chemicals in coastal water far less than that in fresh water.When the environmental system reached equilibrium,the largest sink for PCB28,PCB101,and PCB153 in the littoral areas of Bohai Sea and Yellow Sea was soils.The reserves for PCB28,PCB101,and PCB153 in soils accounted for 96.45%,96.12%,and 95.82% of their total reserves in the environment,respectively.The transfer processes between air and other environmental compartments were the dominant pathways for PCB28,PCB101,and PCB153 inter-media transport in the littoral areas of Bohai Sea and Yellow Sea.Most chemicals entering the Bohai Sea andYellow Sea were transferred by airflow,and the transfer fluxes of PCB28,PCB101,and PCB153 from rural air to coastal water accounted for approximately 97.07%,93.30%,and82.99% of their total fluxes flowing into the sea,respectively.The simulated concentrations of PCB28,PCB101,and PCB153 in fresh water,rural soils,urban soils,and sediments could fit the measured concentrations well,thus verifying the reliability of the model.According to the results of sensitivity analysis,the emission rates,grid dimensions,and transport velocity were the key parameters affecting the model output.Uncertainty analysis showed that the distributions of PCB28,PCB101,and PCB153 concentrations in rural air and urban air were fitted well with lognormal distributions.The ecological risk of PCBs in soils and sediments of the coastal zone were at a low level as a whole,but some areas(Xiaoqing River Basin and Tangshan Area)already had certain potential ecological risk.Considering the bio-refractory,bioaccumulation,and long-distance transport of PCBs,attention should be paid to their threats to human health and ecological environment.