| Nansi Lake in Shandong Province is the largest freshwater lake, but also the largest freshwater lake in northern China. Nansi Lake as an important water channels and flood storage lakes in the south-east-line project, plays a vital role in protection of economic, social stability, development in surrounding areas and ecological civilization. In recent years, eutrophication has become one of the most important water environmental issues of Nansi Lake. Since the state adopted strict standards for pollutant discharge, relevant departments will take corresponding integrated prevention and measures to ensure that the river water into the lake ahead of schedule to achieve criteria Class III ("Surface Water Environment Quality Standard")(GB3838-2002), before the south-east-line project putted into operation. However, Nansi Lake as a large and complex ecosystem, its material, energy and information exchange to the outside are constrained by many factors. In addition to polluted waters through the river into the lake, as well as the non-point pollution, high-altitude air settlement, aquatic metabolism in the lake district and the secondary pollutants of lake bottom sediments are all the factors of the ambient water quality. Under this background, this paper studied one or several aspects of the water environment in Nansi Lake from different disciplines. The study is of great significance in theory and practice. As lake sediments play an important and key role in affecting the lake water environment, they are attracting more and more attention. As the research is incessantly deepened, We now have a better understanding of formation, constituent, characteristic, migration regularity and motion law of lake bottom sediments. Heavy metals in the surface sediments and nutrient salts in the lake district were studied, which can accumulate valuable data for sediment before water transfer and can offer scientific evidence and technique guide for prevention and control of the pollution in major river valleys. Overall, with the impact of increasing the intensity of human activities, water environment in Nansi Lake has already undergone great changes in the past 20 years and this trend is further exacerbated. The engineering construction project, especially the secondery dam of Nansi Lake and the east line of the south to north water project, can change natural landscape. The environmental repercussions are inestimable. Owing to the above factors, an extensive research of water environment in Nansi Lake was conducted. The main conclusions are:1.Content and distribution of nutrient salts in Nansi Lake.The core sediments in lake record more information of environmental changes and the change of nutrient salts content is an important symbol of gradual process of the eutrophication in lakes. N and P accumulated in different depth water sediments record the effect of human activities and nature change on the lake environment. Therefore, establishing and recovering of sequence transformation of the content of nitrogen have an important theoretical meaning for researching the pollution history and can offer scientific evidence for regulation project of lake environment.(1) The content of P in horizontal directionOn the basis of analyseis of the two core sediments collected from Nangyang Lake and Zhaoyang Lake, we concluded that the content of total phosphorus in the cylindrical core from different locations has great difference. The average contents of core-1 and core-2 were 787mg/kg and 590mg/kg respectly. The maximum value of core-1 was 1374mg/kg and the minimum was 512mg/kg, and the maximum value was two times than minimum value. The maximum value of core-2 was 768mg/kg and the minimum was 520mg/kg, and the maximum value was 1.5 times than minimum value.The distribution curve of the content of P in horizontal direction in the two core sediments reflects a trend of a gradual increase from the core at the bottom to the top. The contents of phosphorus in the bottom of the core in Nangyang Lake and Zhaoyang Lake were both about 500-550mg/kg. The content of phosphorus in Nanyang lake sediments increased rapidly, and the phosphorus content from the bottom to top in Zhaoyang Lake also showed a gradual upward trend, but at the bottom and the middle of the performance were not very clear.Overall, the corresponding depth of the phosphorus content of the core in Zhaoyang Lake is below the Nanyang Lake. This may have a close relation to the source of phosphorus and the lake motion law. (2)The content and distribute of total organic carbon and total organic nitrogenous:The different areas of Nansi Lake have different contents of total organic carbon and total organic nitrogenous. The maximum of the total nitrogenous of the sediments in Nanyang Lake was 6056mg/kg about ten times higher than the minimum and the average value was 2240mg/kg. The maximum of the organic carbon of the sediments in Nanyang Lake was 5.61% about ten times higher than the minimum and the average value was 2.21%. The maximum of total carbon in Nanyang Lake was 7.56% and the minimum was 1.48%. The maximum of the total nitrogenous of the sediments in Zhaoyang Lake was 11228mg/kg about ten times higher than the minimum and the average value was 5707 mg/kg. The maximum of the organic carbon of the sediments in the lake was 9.62% about twelve times higher than the minimum and the average value was 5.35%. The maximum of total carbon was 12.37% and the minimum was 6.66%. From the data analysis we can see that there is a world of difference among the different locations of the cylindrical cores collected in the total nitrogen, total organic carbon, and total carbon content. The average of total nitrogen in Zhaoyang Lake core is about 2.5 times than the average total nitrogen in Nanyang Lake. The average organic carbon of the core of Nanyang lake was 2.21%, while the average of the core of Zhaoyang Lake was as high as 5.35%. Across the gap between the minimum and maximum terms, the total carbon, organic carbon and the total nitrogen contents of the minimum and maximum of the core of Zhaoyang Lake, were generally higher than Nanyang Lake. Changes in the vertical, the two cylindrical core of total carbon, total organic carbon, total nitrogen content changes. Changes can be seen that the curve trends are similar to the trends in total phosphorus curve, which is also shown a gradual upward trend from the bottom to the top.Through analyzing the surface and the core sediments in the upper lakes of Nansi Lake, we have come to the conclution:Dmestic wastewater, aricultural wastewater and idustrial wstewater discharged to Nanyang Lake were the main sources of pollution in Nansi Lake. Nutrient elements in sdiments had a stable Vertical distribution and had a clear gradual increase from the bottom to the top, which reflected that the local socio-economic development led to the increasing emissions of nutrients and the accumulation of nutrients in the modern lake sediments.2.The contents and morphology of heavy metals in the sediments of Nansi Lake.In this paper, spatial distribution characteristics of heavy metals in the sediments of Nansi Lake were studied from horizontal and perpendicular distributions two aspects. One Study is the contents and morphology of heavy metals in Horizontal Direction. Forty sediment samples from the lower and upper of Nansi Lake and its main inflow rivers were collected by grabing sampler in three lots. The potential ecological risk index (RI) and geological acumination index (Igeo), as the quantitative diagnostic tools, are used to evaluate the results of chemical analyses. The result showed:the main pollution element in the particles was Cd. And As was the secondary pollution element and the pollutions by other metallic element were slight. The potential ecological risk was quite strong at the upper lake and the estuary, and the ecological risk of the lower lake was very light. Another study is the contents of the sediments in the vertical distributions. According to the requirement of geochemical lake sediment survey, two columnar sediment core with a depth of 0.37m were collected by gravity sampler in Nanyang Lake and Zhaoyang Lake, labeled core-1 and core-2. We take a sample every 0.5 cm in front of 15 cm of each sample pillar and every 1 cm in the back.52 samples registered and numbered were taken from each sample pillar. Analysis of samples includes Org-C, TN, TP,210Pb and heavy metals (including Hg As Pb Cu Ni Zn). Heavy metals were tested in the Institute of Geophysical and Geochemical Exploration (IGGE) of the Chinese Academy of Geological Sciences (CAGS) and the procedure of the research test strictly met the standards of ecogeochemical evaluation method. The conclusions are as follows:(1) The average deposition rate in Nanyang Lake was 0.35cm/a and 0.26cm/a in Zhaoyang Lake. The above mentioned results are almost in agreement with the results of other scholars'studies. On the vertical directation, Hg content was high and the accumulation coefficient reached 12.5. Therefore, it is worthwhile to pay more attention to the concentration of Cu, Hg, and its ecological effect during the process of water environmental treatment and protection in Nansi Lake. Analysis of the speciation of heavy metals are based on 28 surface sediment samples (0-1 cm) collected by this research group in Nansi Lake and its main inflow rivers in September 2005. pH and Eh were measured at the scene and samples placed in sealable bags were transported into laboratory at a low temperature. Then freeze dried, afterward the samples were analyzed for the sediment, the speciation of heavy metals and the content of TOC. The analysis shows:heavy metal artificial pollution in the surface sediments of Nansi Lake and its main inflow rivers-Si River, Jinghang Great Canal, Zhuzhao River, the upper reaches of Guangfu River and the upper south lake and the lower lake was fairly light. The morphology and composition of heavy metal mainly reflect its nature. Cr, Cu, Ni, Zn mainly existedin residual fraction; and Pb and Mn mainly existed in residual fraction and oxidizable fraction. Residual fraction and oxidizable fraction of Cr, Cu, Ni and Zn in the surface sediments of the former canal, lake inlet of the Guangfu river and Baima river increased obviously. The bioconcentration coefficient was high to 10.5. These are important signals for artificial pollution.The most pollution sources were the upper reaches of the Baima river and the city of Jining. As organic matter in the surface sediments decomposes and environmental changes, these heavy metals in water can transform, which has a highly potential ecological risks.3,Analysis and assessment on eutrophication of Nansi lake.With the fast development of agriculture, industry and tourism in Jining and its surrounding areas, enormous quantities of pollutants have been discharged into the Nansi Lake. Now the water quality is rapidly deteriorated and eutrophication is happening. The water deterioration of Nansi Lake limits not only the development of jining society and economy in Jining but also the improvement of millions of citizens'life quality and the function in south-to-north water transfer project. The five typical tests (Chl-a, TP, TN. SD and CODmMn) which have close relation with the eutrophication are monitored with integrated nutrition state index (TLI). According to the calculating data of sample, using the number from 0 to 100 to grade the entrophication state of Nansi Lake. The results indicate that Chl-a, TP, TN and CODMn in Nanyang Lake were all the highest in the four lake areas and were 0.056mg/m3,0.43mg/L,3.38mg/ and 7.3mg/L respectively. Chl-a, TP and CODMn in Weishan Lake were the lowest and were 0.01mg/m3,0.03mg/1,5.16mg/l respectively. The lowest TN in Chaoyang Lake is 1.62mg/1. The trend of transparency is negatively related with the change in Chl-a TP, TN, SD and CODMn. The transparency of Nansi Lake was only 0.47m, the transparency of Chaoyang Lake was as high as 0.72m and the transparency of Weishan Lake was 0.63m. Through the index of entrophication of four lakes in Nansi Lake, the order of the pollution for serious level to light level in the four key river systems is:Nanyang Lake, Dushan Lake, Weishan Lake and Zhaoyang Lake.The major causes of the entrophication of Nansi Lake are not only natural factors but also factitious factors. Low water level, slow rate and long cycle provide the entrophication of Nansi Lake with natural conditions. Human activities make enormous quantities of industrial waste water and domestic sewage and in modern agriculture, overuse of chemical fertilizers and pesticides causes an non-point pollution, which makes the nutrient salts sharply increasing in Nansi Lake. All of these lead to the eutrophication of water bodies.4,Research of the mechanism of adsorbing heavy metal ions onto chitosan and clean Si. Chitosan is an important class of natural polysaccharides derivatives, which plays an important in wastewater treatment, precious metal enrichment, removal of heavy metals in lake sediments and ecological restoration. Because of its repeating unit with the active groups (such as amino, hydroxyl), Chitosan can react with a variety of metal ions such as Hg2+, Cd2+, Cu2+, Ni2+ and Zn2+, then forming a more stable chelate. Since the electronic structures of various metal ions are different, the stability of complexes formed has a big difference. By chemical modification of chitosan, we can change the stability of chelate formed for selective adsorption and industrial operations. In the past few decades, a series of studies of Chitosan adsorbing metal ions have been done in different environments. It is generally believed that the mechanism of Chitosan adsorbing metal ions would be chelate mechanism and electrostatic attraction mechanism. In neutral solution, the interaction between Chitosan and heavy metals is chelate mechanism. However, great difficulties have been encountered to determine the interaction mechanism between metal ions and the chitosan because of the restrictions of experimental methods. While the Quantum Chemical Method to research of the mechanism has become a powerful tool.To find out the nature of interaction between heavy metal ions and chitosan and to provide the theoretical basis for the removal of heavy metals in lake sediments, the density functional theory (DFT) was first introduced in to study the interaction betwwen ions (Hg2+, Pb2+ and Ag+) and chitosan and calculate the chitosan adsorption energy. The results show that transition metal ions (Hg2+, Pb2+ and Ag+) are mainly adsorbed on the amino nitrogen atoms and hydroxyl oxygen atoms of the chitosan, and have strong interaction with oxygen atoms in the chitosan main chain. The binding energy of Hg2+ and Pb2+ ions is much greater than Ag+. The interaction mechanism between Hg2+, Pb2+ and Ag+ and other heavy metal ions and chitosan is mainly electrostatic interactions.
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