Sedimentary Record And Environment Risk Evaluation Of Metals In The Sediments Of Hulun Lake

Hulun Lake is the post for migratory birds from Oceania and Northeast Asia and plays an important role in regulating the climate of northern China.With the rapid development of human society and economic,the ecosystem of the lake has been affected.The sediments of the lake ecosytem is of significant in dealing with the contaminants.Hulun Lake is the research lake of this thesis.Firstly,the space distribution and environmental pollution evaluation for heavy metal in the sediment surface were analyzed;The chronostratigraphy of sedimentary strata was reconstructed by radioactive nuclide(14C).The combined the model of index of geoaccumulation based on blind number theory with certain assessment is used to make result more efficiently.The space distributions of the heavy metal of Cu?Cd?Zn?Mn?Fe?Pb in the sediment surface basically have the similar trends:it which showed a stepwise downward from the northwest to the southeast,The heavy metal contents in estuary and shallow water is considerably below the northwest region where are the tourism areas.Three different kinds of heavy metal pollution evaluation methods have got the consistent results.Cd is at the level from slight inclined to moderately pollution,while Cu?Zn?Mn?Fe?Pb are at the level from clean to slight pollution.Hulun lake is belongs to medium pollution level.The results revealed that metal pollution could be divide into three stages:stage 1,(1760?2015)the values of EF about Zn?Pb?Cd are reduced significantly in fluctureation that might be caused by human activity.stage2,(750?1258)the value of EF changes less,stage 3,(640?1048BP)is marked with dramatically wave that caused by global climate change.In the method of principle component?correlation analysis and cluster analysis.We can found that heavy metals divided in two parts,part1 Cu?Pb?Cd?Zn,part2 Fe and Mn.There are two sources of heavy metal one is from natural pedognic and the other is from continental runoff and atmospheric deposition.