Characters Of Carbon And Nitrogen And Sources Analysis Of Surface Sediments From Lakes In The Middle Of Yantze River

A variety of pollutants were gathered in freshwater lakes,which are organic carrier of environmental pollution.While surface sediment can reflect lakes'condition of nutrition in a short time.The study of sediment can understand the ecological changes of surrounding environment,and it is also important to analyze the impact of human activities on the lakes.Hubei province is a significant part in the middle of the Yangtze River,where a large number of lakes are distributed,which is one third of middle of the Yangtze River.However there is not any large-scale study of sediment of Hubei province.We selected 18lakes in the middle of the Yangtze River,whose water area are greater than 10 km².In the present study,the content and isotope values of the total organic carbon and total nitrogen from sediments were investigated in 18 shallow lakes,which was aimed at understanding the different and common points,which can provide a reference of prevention and treatment of lakes in the middle of the Yangtze River.Some conclusions are as follow:?1?The content of TOC and TN of lakes in the middle of the Yangtze River lie up a mean level.But the contents are not used for giving a explanation to the pollution condition of lakes because of the differences of geographic position and properties.Deep lakes have a higher content of TOC and TN due to a more gentle disturbance and boundary between sediment and water,but have a better water quality.In contrast,large shallow lakes and rivers have a lower content of TOC and TN.The Organic Index?OI?,which is always used for evaluating the condition of lakes'sediment,is better suitable for large shallow lakes but not middle and small lakes.In the end,the Evaluation of Sediment from Ontario,Canada was adopted.And the results said the sediments of lakes in the middle of the Yangtze River have been polluted,but majority of benthic organism can resist it and the community have not been damaged.?2?The?¹³C or with C/N were used for analyze the sources of lakes in the middle of the Yangtze River.The?¹³C of C4 plant was separated from the sediments of lakes,and the C3 and C4 plant were excluded by the plot,which indicates phytoplankton,soil organic matter and aquatic vascular were the main sources of the surface sediments in the lakes.There are 3 type of lakes by quantitative disposal,which are respect type of interior sources,external sources and both.The former,for example Lake Chidonghu and Lake Yezhuhu,both have good ecological environment,but the others have been disturbed in varying degrees by people,which indicates the outside disturb can be reflected by sediment.And the chemical fertilizer,domestic sewage and animal waste were main sources of N in the lakes.