A COMPARISON STUDY OF ECOLOGICAL ASSESSMENT MODEL ON HEAVY METALS OF OFFSHORE SEDIMENTS

Heavy metal contamination in offshore is a worldwide problem,because these metals are generally indestructible and most of them can cause heavy damages to coastal ecological environments and systems.Those pollutions are mainly transported into coast and adjacent sea by input and/or industrial wastewaters discharge.Most Heavy metals,especial for particle-active components,are deposition in coastal sedimentary environment.Sediments are the main repository and source of heavy metals in the aquatic environment and play an important role in the transport and storage of potentially hazardous metals.The paper reviewed the ecological risk assessment methods on heavy metals in coastal sediments,including how the chemical forms or type of the binding of metals act on bioavailability,pollution degree evaluation by contamination index,and ecological effect assessment of heavy metals based on ecological risk index.The advantages and disadvantages of those methods were also compared and discussed.Assessing sediment pollution by using the heavy metal chemical form might not firmly guarantee the occurrence of deleterious ecological effects.Contamination index could hardly give comprehensive and systematic information about bioavailability of heavy metals.The ecological risk index have been derived with a variety of both theoretical methods that rely upon equilibrium partitioning models and empirical methods that rely upon analyses of matching,field-collected chemistry,and biological effects data.But evaluation on the potential ecological risk of heavy metals based on ecological risk index might lose information about environmental effects on heavy metals.To sum up,the evaluation together with the different methods should be a useful crosscheck for us in the assessing process.