Studying On Release Characteristics And Flux Of Inorganic Nitrogen From Sediments In Erhai Lake

Nitrogen content is the most important nutrition elements in the lake ecosystem, which can be directly involved in the nitrogen cycle of water environment system.Although nitrogen play an important role in primary productivity in aquatic ecosystems, it could to cause water quality of lake deteriorate and eutrophication. Therefore, the content of sedimentary nutrient, the character of distribution and the character of inorganic nitrogen release in lake water is the important basis for the study of the rules of migration and transformation of nitrogen nutrients and also plays an important role in the study of lake eutrophication mechanism in lake water system.This paper relying on the issues of Erhai Lake," The ecology of lake water, the research of the change of internal-load, the technology of anti-degradation and the model engineering(2008ZX07105-005)",which is the special significant water projects of the state.This paper do the research on the distribution of nitrogen forms in the Erhai sediment and its effect of biogeochemical cycle for the first time. This paper investigate the nitrogen content in sediment, distribution, characteristics and quanlities of inorganic nitrogen release and the historical process of human pollution, providen a frame of reference for for future prevention and treatment of Erhai Lake eutrophication and anti-degradation of the lake water environment.We investigate the distribution of nitrogen concentrations in sediments and characteristics of the release of inorganic nitrogen and the flux of nutrients in sediment-water interface, the main obtained results are as follows:(1) Total nitrogen content of the whole Erhai Lake in northern West Bank is highest in northwest region,the southern region second highest and in the north region east and central areas is low. This study shows that Erhai Lake lake pollution is mainly affect by runoff into the lake and contaminated material in runoff of Erhai lakeis the primary pollution;(2) The release potential of sediment ammonia in Lake Erhai is lower than the release potential of the Yangtze River,is about 30% of the shallow of Yangtze River. Release potential of ammonia in Sediment of Erhai Lake is not obvious; (3) The maximum emission of ammonia in Erhai sediments is about 30 percent of the sediments of Yangtze River shallow. Release of ammonia nitrogen mainly focus on 5min, then attended to equilibrium gradually;(4) There is a certain tendency thant the NH4+-N in Erhai sediments release to the overlying water, which reach the maximum near Dali City in the whole lake range.This is the evidence pollution caused by urban life and industriy production have major impact on the concentration balance of nitrogen nutrients of water environment system in this region;(5) When subsurface sediment directly contact with the water, release ability of NH4+-N become stronger. These results showed that in the sediments and overlying water nitrogen nutrient exchange process, nutrient release of these sediments have certain shield effect;(6) In the 8cm place of Erhai sediments, the release quantity of NO3--N reach maximum; and with the increase of depth, release quantity does not increase. These results showed that Nitrogen in the upper sediment mostly exists in the form of NH4 +-N, which can be absorbed by plankton; However, as the depth increases, more nitrogen in sediments mostly with stable NO3-N form exists.From the above, Erhai is now in the early eutrophication. In the northern West Bank area and the southern region mainly by the industrial production and domestic pollution is more serious.In the whole Erhai, nitrogen release quantity of the Sediment is not significant, nitrogen nutrient release of the surface sediment has certain shielding effect. Therefore, the release of nitrogen in the sediment studies and sediment-water exchange fluxes of the interface reveals the current status of Erhai Lake, which will help solve Solve Erhai lake eutrophication.