TOC,C/N Ratio And δ¹³Corg Characteristics Of Lake Surface Sediment In Northern Tibetan Plateau And Its Environmental Signincance

The special geographical position of Tibetan Plateau gives its important role in the climatic and environmental research. The organic carbon isotope(δ13Corg), total organic carbon(TOC) and carbon-nitrogen ratio(C/N) in lakes sediment can reflect the primary productivity and vegetation types in lakes and watersheds, and also reflects the state of conservation with organic sediments after deposition, and preserves the lake and watershed biological and ecological environment and information of climatic and environmental changes. Total organic carbon(TOC) and organic carbon isotope(δ13Corg) values in lake sediments have a better indicative implications for regional climatic environment. carbon-nitrogen ratio(C/N) in lake sediments is the main basis for judging the lake organic carbon sources.In this paper, we selected52lakes in Northern Tibetan Plateau and collected52surface lake sediment samples. By measuring the content of total organic carbon(TOC), carbon-nitrogen ratio(C/N) and organic carbon isotope(δ13Corg) values and analyzing its variation and factors. Besides, we researched the sources of the lake organic carbon. Finally, we get the following conclusions:First, the content of total organic carbon in surface sediments from Northern Tibetan Plateau differs largely, most of it range from1%to3%, The change of its value can reflect environmental temperature in the area by means of the growth of aquatic organisms and terrestrial plant around the lake. The temperature and effective humidity play a major impact on the content of organic carbon in surface lake sediments from Northern Tibetan Plateau, while the grain size of surface lake sediments and the existing quantity of aquatic plants are secondary factors.Second, the majority of carbon-nitrogen ratio(C/N) in surface sediments from Northern Tibetan Plateau ranges from10to20, It shows that the organic matter is from phytoplankton or aquatic plants,or mixed with terrestrial plants.Third, Most of the δ13Corg values for surface sediments from Northern Tibetan Plateau ranges from-20‰to-27%o, The δ13Corg values from Lake sediments can indicate the climate in the way of the growth of living things around the lake The temperature and precipitation and the different sources of the lake organic carbon is the main reason for causing the difference of the value of δ13Corg..Fourth, Using organic carbon isotope (δ13Corg) values and carbon-nitrogen ratio (C/N) to judge the source of organic carbon in surface sediments from Northern Tibetan Plateau. The result shows that the organic matter external source is mainly from C3plants while internal source is aquatic plants, phytoplankton and lacustrine algae. For most lakes, its main organic matter source from plankton algae and aquatic plants, or mixed with C3plants as organic matter source.