Effect Of Perinereis Aibuhitensis On Bioavailability Of Heavy Metals In Estuarine Sediments

Sediment is not only the sink and source of heavy metal contaminates in marine environment,but also the habitat of benthic organisms.Particle mixing and water circulation in burrow caused by bioturbation could influence the behavior of heavy metals in sediment.Investigating the change of bioavailability of heavy metals in sediment under bioturbation could provide necessary theoretical basis for evaluating the environmental quality of heavy metals in sediment.This study investigated the effect of bioturbation on the geochemical speciation of heavy metals in sediment and release of heavy metals in sediment to overlying water and porewater through the bioturbation experiment,and Perinereis aibuhitensis,the dominant benthic organism in China coastal sediments,is selected as test in this study.Based on this,the effect of bioturbation on bioavailability of heavy metals in sediment is investigated.The conclusions are as follows:The result of toxicity experiment of heavy metals in two exposure mediums indicated that P.aibuhitensis exhibited extraordinary tolerance to heavy metals.The 96 h LCso of Cd,Cu,Pb in seawater were 24.5?3.85?1063 mg/L(calculated by detected concentration)against P.aibuhitensis.The 96 h LC50 of Cu in sediment was 667 mg/kg against P.aibuhitensis.The toxicity between metals was synergetic in both seawater and sediment and crude oil could inhibite the toxicity of metals in sediment.Metal contents in P.aibuhitensis were significantly correlated with the lethal effect and the bioaccumulation of metals in P.aibuhitensis explained the synergetic effect between metals and the inhibited effect of crude oil to metals.The proportions of exchangeable Cu and the carbonate adsorbed Cu,Cd,Pb were significantly increased and the proportions of Fe-Mn oxides adsorded Cd and organic matter adsorbed Cd,Pb were decreased under bioturbation by P.aibuhitensis.Cu in porewater were significantly decreased.Carbonate adsorbed Cu may be the release source of Cu in porewater and organic matter may be the adsorbed phase.Organic matter adsorbed Zn may be the release source of Zn in porewater.The release of heavy metals from sediment to overlying water were enhanced under the bioturbation by P.aibuhitensis.The dissolved Cu,Zn,Cd,Pb in overlying water in bioturbation group were significantly higher than that in control at 30 d.Mn oxides adsorbed metals may be the major release source of metals from sediment to overlying water.Overall,heavy metals in sediment transformed from active speciation to inert speciation under bioturbation and the bioavailability of heavy metals was weakened by P.aibuhitensis.