Chemical fractions of heavy metals of sediments in Meiliang Bay, Lake Taihu and tracing for its pollution history

The concentrations of heavy metals in different Chemical fractious of sediments collected from the Meil- iang Bay,Lake Taihu,were measured.Sequential extraction method was used to gain the concentrations of sedi- ment-bound heavy metals in six fractions,i.e.,soluble,exchangeable,bound to carbonates,bound to Fe-Mn ox- ides,bound to organic matter,and residual.By use of ~(210)Pb and ~(137)Cs activities to obtain age of sediments,tempo- ral variations of heavy metals in different fractions and their enrichment factors were shown.Among them,varia- tions of heavy metal concentration in Fe-Mn oxides fraction of the sediments can be used to reflect contaminant in- put by human activities.On the basis of our data,the history of catchment human activities was divided into three periods,among which the most heavily affected by human activity was from 1977 A.D.to present.By comparing the concentrations of heavy metals in Fe-Mn oxides fraction with historical industrial product values of Wuxi City, their similar trends suggest that the increasingly environmental pollution is due to a fast development of industries a- round northern Taihu region,further indicating that heavy metals was mainly as a form of bound to Fe-Mn oxides into the Lake Taihu ecosystem.