Abstract: In April,July and November 2002 and April 2003,a quadrat investigation of macrobenthos was conducted at four sampling profiles in the intertidal flat of Yangtze Estuary.The concentrations of Cu,Pb,Fe,Mn,Zn and Cr in several high biomass macrobenthos were determined,their absorbed amounts per square meter were calculated,and the biological quality of Corbicula fluminea and Siliqua minima was evaluated.The results showed that C.fluminea was widespread in the intertidal,especially in the low tidal flat of Yangtze Estuary,and heavy metals were mainly concentrated in its soft tissues.C.fluminea could selectively absorb Cu,leading to the little variation of Cu concentration in the tissues of C.fluminea sampled from different coastal region.Mollusks Rissoina sp.and Bullacta exarata,and all crustaceans could markedly accumulate Cu in their bodies,and the BSAF value reached 2.97～7.97.The mollusks and crustaceans had the greatest absorption of Fe per square meter,followed by Mn,Zn and Cu,and Pb and Cr.The amount of Cu,Pb,Fe and Cr absorbed by B.exarata larva from per square meter intertidal flat was obviously higher than that by other macrobenthos,while the absorbed amount of Mn and Zn in B.exarata larva was less than that in C.fluminea collected from XuPu.The concentrations of Pb and Cr in the soft tissues of C.fluminea and S.minima were relatively lower in the intertidal flat of Yangtze Estuary than in other coastal and estuarine areas,and those of Cu and Zn were also low but at appreciable level.Compared to the criterion for marine biological quality in China,the edible soft tissue of Corbicula fluminea and S. minima in the tidal flat of Yangtze Estuary was relatively safe for human beings.

Key words: Methane, Flux, Seasonal variation, Soil Eh