| Eutrophication of Taihu lake is one of the important water issues in our country, the northern water in Taihu Lake is relatively seriously influenced by human, at the same time, the bad water exchange ability has intensified the water eutrophication. Therefore this paper made the northern region of Taihu Lake as the research object, the distribution of nutrient, the adsorption/desorption of sediment and dredging scope and volume were analyzed, Designed for the governance of eutrophication of Taihu Lake and its ecosystem restoration to provide the theory basis and the data support, giving the advises to lake sediment dredging scientifically.This paper made northern three regions Taihu Lake (Zhushan bay, Meilaing bay, Gonghu bay) as the research object, collected altogether33points, including overlying water, interstitial water and sediment samples, through analyzing nitrogen content of different forms in the overlying water, we found that the lake water in northern lake all belongs to inferior to the V kind of water, the distribution of all forms nitrogen almost became successively little from Zhushan bay to Meiliang bay and then to Gonghu bay; the TN in interstitial water presents the tendency of decrease gradually from center to around, ammonia nitrogen presents the tendency of increase gradually from north to south, and nitrate nitrogen is contrary to ammonia nitrogen. Through monitoring to the different forms of nitrogen in the surface sediment, we found that the sediment of Zhushan bay, Meiliang bay and Gonghu bay all belonged to contaminated sediments from the view of the average total nitrogen content of sediments in three lakes, the KTN content of surface sediment in coast is higher than the middle of lake. Exchange ammonia and nitrate nitrogen distribution trends are similar and present tendency of decrease gradually from west to east; analysis the relationship of different forms nitrogen of overlying water-interstitial water-sediments in northern three regions, through the related analysis, We found that exchange ammonia nitrogen has certain decision effect to dissolved ammonia nitrogen, and dissolved ammonia nitrogen has certain decision effect to ammonia nitrogen to overlying water.We carried on nitrogen adsorption/desorption simulation experiments using15sites in northern three regions,and found that the equilibrium concentration of adsorption/desorption was less than the nitrogen content in overlying water, the sediment release nitrogen to the overlying water, in other words, the sediment is the nitrogen "source" of overlying water. Making the adsorption quantity and adsorption/desorption initial concentration the linear fitting, and got the adsorption/desorption efficiency and local absorption nitrogen content. There are large differences in local absorption nitrogen content, Meiliang bay is the largest, GongHu is the minimum; in adsorption/desorption process, the difference of adsorption/desorption efficiency is not big, but Gonghu bay which belongs to grass type has more adsorption space than Zhushan bay and Meiliang bay which belong to algae type.Finally, according to the sediment dredging technology, based on the first part that is the lake surface sediment pollution state of Taihu Lake, we calculated that the dredging area is335.68km2in the northern three lake, accounting for72.30%of the total area of three areas, and Zhuanshan bay needs dredging90.57km2, all needs to carry out the dredging, MeiLiang bay should be106.87km2, accounting for50.34%of the total area of MeiLiang bay, Gonghu needs138.24km2, accounting for84.43%of the total area of Gonghu bay. At the same time using inflection point method to find out the depth of the dredging sediment, Zhushan bay is0.17m, Meiliang bay is0.17m, Gonghu bay is0.25m, and then we can calculate the dredging volume of Zhushan bay, Meilaing bay and Gonghu bay is1.54×107m3,1.82×107m3,3.46×107m3respectively... |
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