Influence Of Benthic Bioturbation On Transportation Of Sediment-associated PBDEs In Estuary

Polybrominated diphenyl ethers(PBDEs)is a new type of persistent organic pollutants which has been ubiquitous in estuary and littoral sediment.Bioturbation can affect transport and vertical distribution of PBDEs in sediment and would increase the release of PBDEs from sediment to water,which will lead to negative effects for the health of aquatic organisms living in the water,thus threatening the health and safety of the entire aquatic ecosystem.In this study,Perinereis aibuhitensis as a dominant species from estuarine area was applied to explore the influence of bioturbation on transport and release behaviors of PBDEs from a field estuarine sediment,which would contribute to a deep understanding on the environmental effects and ecological risk of sediment-asscociated PBDEs.Through a laboratory microcosm experiment,the research showed that P.aibuhitensis bioturbation could promote the deposited particulate matter resuspension.P.aibuhitensis bioturbation could make TSS concentration in overlying water reach the highest value of 62.36 mg/L.Comapred to the TSS highest concentration value of 17.78 mg/L of group with no P.aibuhitensis bioturbation,TSS concentration was significantly improved.In addition,P.aibuhitensis bioturbation could also significantly improve DOC concentration in overlying water.Deposited particulate matter of the resuspended process would lead to the release of organic carbon from the sediments into the water column,thereby increasing the DOC concentration of overlying water.P.aibuhitensis bioturbation could improve the concentration of particulate PBDEs in overlying water,since PBDEs has a strong lipophilic hydrophobic and is easily adsorbed by deposited particles,which lead to particulate PBDEs from deposition layer into the water layer with P.aibuhitensis bioturbation,improving the concentration of particulate PBDEs in overlying water.Moreover,P.aibuhitensis bioturbation could also improve the concentration of dissolved PBDEs in overlying water,because P.aibuhitensis bioturbation behaviors could change physical and chemical properties of sediment,thus contributing to the desorption behavior occuring of PBDEs from deposition layer into the water layer,increasing the concentration of dissolved PBDEs in overlying water.Dissolved and particulate PBDEs concentration in overlying water were also affected by the burial depth of PBDEs,P.aibuhitensis density and other factors.For example,particulate PBDEs concentration in overlying water was reduced with increasing the burial depth of PBDEs in sediment,while the concentration of dissolved PBDEs in overlying water was not significantly affected by the burial depth of PBDEs in sediment.In addition,high-density P.aibuhitensis bioturbation did not significantly improve the Dissolved and particulate PBDEs concentration in overlying water.In this study,P.aibuhitensis bioturbation also increased the release flux of PBDEs from sediment to water,and the flux was inversely related to the burial depth of PBDEs.In addition,P.aibuhitensis bioturbation could affect the longitudinal distribution of PBDEs in sediment.For shallow burial of PBDEs in sediment,the P.aibuhitensis bioturbation could promote PBDEs transport from shallow layer to deeper layer direction,and for deeper burial of PBDEs in sediment,P.aibuhitensis bioturbation could also contribute to its movement to shallower layer direction.In addition,high density P.aibuhitensis bioturbation did not significantly affect the longitudinal distribution of PBDEs in sediment.