| Hulun Lake is the biggest lake with typical characteristic of grassland in China, which is located in semi-arid region of inhigh latitude inland area. This area is in the temperate continental climate, four distinct seasons. Hulun Lake has been regarded as World Biosphere Reserve, and listed in the international key wetlands by UNESCO. The flakes has superior natural conditions with rich fishery resources, and plays a key role in environmental protection[1]. An important ecological defence for northeast and north China is contributed by Hulun Lake wetland and Daxinganling forest. So that the systematical study of Hulun is of great significance.Based on the study results of geochemical behavior of nitrogen, phosphorus and other biogenic elements in the overlying water and sediment of Hulun Lake, we could develp the solutions of prevention control and treatment of eutrophication, as well as its scientifical utilization and protection strategies for lakes and wetland resources.we obtained following conclusions:1. To analyze the concentrations of total nitrogen(TN), total phosphorus(TP) and chlorophyll a (Chla) in Hulun water varied in four seasons, we concluded as following: the concentration00000 of nitrogen (TN) and phosphorus (TP) in Hulun lake exceeded the standard rather seriously, and the concentration of chlorophyll a (Chla) varied obviously with the seasons; For spatial variation, the concentration of TN spreaded outward from the central of the lake, and then a reverse process with seasons; TP concentration kept steable in spring and summer, and spreaded outward from central of the lake in autumn and winter; The concentration of Chla exhibited a varation tendency of south-north-southeast-east.2. According to the environmental quality standards for surface water, it showed that the nitrogen pollution was serious in Hulun lake, ranging classifying level V on average. Worse yet, the phosphorus pollution is more serious, as inferior level V of maior sampling points water. Above all, it was mild eutrophic in spring, summer and autumn in the meothod of nutritional status index, in comparison, it was moderate nutrition in winter.3. In the method of Principal component to analyze the water quality, we concluded that there are 8 factors effecting Hulun Lake:acidity (PH), dissolved oxygen (DO), total dissolved solids (TDS), salinity (SAL), chlorophyll a (chla), total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD). The major water pollutions was influenced by eutrophication, salinization, and organic.4. Analyzed the concentration and varation characteristics of water and ice, including the total nitrogen, total phosphorus, total solubility phosphorus and solubility orthophosphate, it showed all water quality indicators exhibited as water> ice. And all concentration index of water are similar to the ice’s in different areas. Above studies, we could concluded that the polutants inputed to Hulun was more than the pollutants absorbed.5. Analyzed the distribution of total nitrogen (TN), total phosphorus (TP) and organic matter, it showed a stepwise downward tendency of the distribution of TN, TP and organic matter in the surface sediments from the northwest to the southeast. The maxima index was displayed in the center of the lake in northwest region, and the minimum distributed in the estuary and shallow water. The vertical distribution of nitrogen content in sediment cores was decreased by deepth increased, and mainly on the surface layer. Such distribution of phosphorus displayed a large depth differences, which may be caused by variety of factors as sedimentary environment, early diagenesis and human activities. The content of organic matter reduces with depth increasing, which was similar to nitrogen. Local fluctuations may be related to the accumulation of animal and plant residues in this year.6. What we could get from the Hulun anaylsis of coupling relationship of surface sediments contains carbon-nitrogen-phosphorus and environmental significance were that:a higher degree of eutrophication of the lake area by N/P ratios, and the lower degree in the southeast region; The organic matter in the lake might be contributed by aquatic organisms and terrestrial input, which was the dominant source, indicated by ratio of TOC and TN. The ratio of TOC and TP also indicated that sediment organic matter effected the varation tendency of TOC/TP ratio dominantly.7. According to the evaluation of current environmental status of the lake, we found the benthic threaten from eco-toxic effected by total nitrogen and organic has gone from bad to worse. And the worst conditions might effect the benthic communities.Most of the lakes were contaminated by organic pollution and organic nitrogen pollution, except the lakes located in the southeast are or the mouth of the lake. |
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