Research Of Nutrient Element Geochemistry Circulation And Heavy Metal Pollution In Plateau Typical Lakes In Inner Mongolia

The climate of Inner Mongolia plateau is chill and dry, and has few precipitation though out the year. The lakes form different and freeze long time during the winter. In recent years, plateau lakes present some special features at water environment carrying capacity, geochemical cycle of water body and sediment, contamination of heavy metal sediment and nutrient transformation at low temperature and icebound time due to the development of economy and some setting rules. Sediment contamination is one of important research contents for lake pollution, also a focal environmental issue in the wide world. As a main part of Lake Ecosystem, sediment is not only the point of nutrition material cycle, but also the important reservoirs of contaminant. During the interaction between water body and sediment, part of nutrient in sediment release to the water body and change to internal loading of lake nutrient when external loading are controlled. At present, some researchers did much about the contamination of lake sediment at south lakes-such as Chao Lake, Taihu Lake, Dian Lake and East Lake, but few at plateau lakes of cold and arid regionsIn this thesis, Wuliangsuhai Lake and Hulun Lake, which are two typical lakes in Inner Mongolia, are the main study object. Base on the researches of water environment and area hydrology, water quality and long term climate monitoring station, and according to water quality of lakes, sediment and the factors of hydrology and climate, the features of irrigation lakes and prairie lakes, discuss the specific features of argument for eutrophication and the heavy metal contamination.It shows you the situation of Inner Mongolia plateau lakes water pollution and organic contamination of sediment and heavy metal, tells you the relationship between sediment nutrient and heavy metal and other metallic element. It presents the distribution regularity between water body and ice body in low temperature and icebound time aim at the features of plateau lakes. It can be concluded in three results as follows:Firstly, the Geostatistics and Arcgis was used for the kriging spatial interpolation about nitrogen and phosphorus in Wuliangsuhai Lake and Hulun Lake. The result presents that the spatial and temporal features are different between Wuliangsuhai Lake and Hulun Lake due to the different location, icebound time and growth period.After some surveys about plankton, meiobenthos and planktobacteria at Wuliangsuhai Lake and Hulun Lake, it shows phytoplankton changing to anti-pollution and the variety and quantity of meiobenthos are gradually reducing. And planktobacteria bloomed at Wuliangsuhai Lake.The evaluation of water pollution reveals that Wuliangsuhai Lake is a severe eutrophication lake and is influenced much by humans. But Hulun Lake is a medium eutrophication lake and is not big influenced.Secondly, after conducting the quantitative analysis of total nitrogen, nitrogen form(nitrate nitrogen, ammoniacal nitrogen),total phosphorus and organic matter, and figuring out the horizontal and vertical direction distribution characteristics of important elements, also, base on the research of the coupled relation among sediment C-N-P and their environment, it shows that Wuliangsuhai Lake is in a clean condition, as its average value of organic index is0.42, but it is in a contamination of organic nitrogen, as its w(ON) average value is0.17%. For Hulun Lake, it is in a less clean condition, as its organic index is0.18. That its w(ON) average value is0.125%means that it is within a clean category; However, it is seriously polluted when the sampling point is examined.In general, it has a similar tendency between organic pollution and organic nitrogen pollution. The organic pollution and organic nitrogen pollution of Wulaingsuhai Lake are both higher than Hulun Lake.Thirdly, the spatial and temporal characteristics of lake sediment’s heavy metal shows the most serious contaminant are Hg and As at summer time, but Cd at winter in Wuliangsuhai Lake. The heavy metal pollution belongs to medium level at Wuliangsuhai Lake but light level at Hulun Lake except Cd.Lastly, it analyzed the difference of the nutrient distribution in water body and ice body at the low temperature and icebound time for Inner Mongolia plateau characteristics.In sum, base on the geochemical cycle features of water body and sediment in Wuliangsuhai Lake and Hulun Lake, the distribution characteristics, source, pollution level and the influence to eutrphication were discovered. These are definitely provided suggests to water pollution control, Lake ecosystem preserve and wetland repair. These sure have big significance towards environmental improvement and protection of Lakes in cold and arid regions.