A Study On The Speciation And Migration Of Heavy Metals In Sediment Cores From Dashentang Coastal Zone And Liaohe Estuary

Coastal zone is an active region with strong land-sea interaction,which is sensitive to natural variability and human activities.The sediments can adsorb and enrich heavy metals.The distribution of heavy metals in sediment reveals provenance and controlling factors about itself.It is important to study the characteristics of heavy metals by sequential extraction procedure.Two sediment cores were collected in this article to determine the total organic carbon(TOC),acid volatile sulfur(AVS),simultaneous extraction metal(SEM),granularity,and total concentration and speciation of heavy metals in sediments from Liaohe Estuary and Dashentang Coast zone.Using multivariate statistical analysis and the diffusion flux,migration of heavy metals in sediments is studied.Various evaluation methods were also applied for environmental assessment.The results are as follows:1.The contents of heavy metals in sediments from Dashentang Coast zone decrease with the depth except Cd.The concentrations of these metals increase rapidly from the bottom upwards and then decrease in the sediments from Liaohe Estuary.2.The residual fraction of Cr,Cu,Pb and Zn were all dominant both in two study areas.Acid extractable fraction is dominated for Cd.3.Various evaluation methods all reveal that the pollution of Cd in Dashentang Coast zone is in a low level.However,because of the proportion of non-residual Cd,which is mainly related to human activities,is relatively high,the pollution of Cd in Liaohe Estuary is serious.The other heavy metals in the two areas were basically in a state of no pollution or light pollution.4.Multivariate statistical analysis reveals that the heavy metals of Cr,Cu,Pb,Zn in Dashentang Coast zone are mainly derived from the weathering of land rock,and most of Cd and Cr,Cu,Pb,Zn in acid extractable state are associated with human activities.There is a significant correlation relationship among five heavy metals in Liaohe Estuary,suggesting that all of the five metals might be mainly from the weathering of continental rock.Non-residual heavy metals might be derived from human activities.The migration of heavy metals might be influenced by TOC and AVS in Liaohe estuary zone.