The Study On The Geochemical Characteristics Of Nitrogen In Four Typical Lakes Of Inner Mongolia Plateau,China

Inner Mongolia plateau lakes which are important ecological treasure house in Inner Mongolia autonomous region and the northern China play an increasingly vital role in environmental protection, climate regulation, human production and living and economic development. So it is of great significance to research lake wetlands in Inner Mongolia plateau.Nitrogen as one of the main nutrient elements plays an important role in eutrophication of lakes. Sediments are important sources and sinks of nitrogen,the endogenous release of nitrogen in the sediment will be the main reason for lake eutrophication after the external pollution was controlled effectively. So it is not only of great significance to manage lakes and control pollution,but also can provide reliable scientific basis for prevention of eutrophication by contrasting the contents, the forms and distribution patterns of nitrogen in sediments of different lakes.This paper is on the basis of the geochemical characterastics of nitrogen, combined with the early research, and systematically compare nitrogen contents and form distribution in four typical Inner Mongolia plateau lakes.Moreover,it compares nitrogen pollution and eutrophication level in different lakes, and the correlation between various forms of nitrogen and the organic carbon in sediments are discussed. Main achievements are obtained in this study as follows:1. The mechanism of diversity on geochemical characteristics of nitrogen was first explained in sediments of four typical Inner Mongolia plateau lakes.It shows that the natural and geographical conditions, physical and chemical properties, primary productivity, sediment grain size of lakes and human activities are all important factors affecting geochemical characteristics of nitrogen in sediments.2. The order of total nitrogen content in the four lakes are as follows: DLNE>HLH>DH>WLSH,which is the same with the order of organic nitrogen and nitrate nitrogen contets.But the order of ammonia nitrogen is different as follows:HLH>DLNE>WLSH>DH.3. Organic nitrogen in the four lakes is the dominant form of nitrogen, and it accounts for more than90%of total nitrogen. The ammonia nitrogen is the dominant form of inorganic nitrogen in WLSH, DH and HLH.The nitrate nitrogen is the dominant form of inorganic nitrogen in DLNE.4. According to the grading standards of organic nitrogen contamination and organic index evaluation in sediments, it reveals that the nitrogen pollution level in the three algae-type lakes is higher than the grass-type lake called WLSH.5. It shows that DH reaches basic balance between endogenous and exogenous organic matter;WLSH and DLNE is given priority to endogenous organic matter and HLH is given priority to exogenous organic matter.