Research On The Degrades Mechanism And The Repairing Theory And Technology For Lake Ecosystem

The lake ecosystem is regarded as the important component of the aquatic ecosystem, it offers the essential material guarantee for the economic development and people's lives of the lake regions, it has lots of important functions, such as supplying water, preventing flood, shipping and regulating some climate, etc. However, with population's constant growth, the rapid development of industrial and agricultural production, the mankind productions and lives produce a large number of offal discharged into the lake ecosystem, it becomes the main source of lake ecosystem nutrition salt. Environmental question such as nationwide lake eutrophication, lake water salty in arid area, lake deposit, withering etc appears constantly. Especially to most shallow water type lakes and small-scale lakes near city lying in the east plain of our country, the eutrophication question of the lake is outstanding day by day, and it has already become the most outstanding lake ecological environment problems and urgent problems to be solved at present in our country.Lake eutrophication is the external manifestation of the lake ecosystem structure is destroyed and the function lost, and the lake ecosystem degradated and the stable state shifted, it is the results of pollutants such as nutrition salt (the phosphorus, nitrogen) etc, being accumulated constantly among the water bodies. The investigation result to 25 large-and-middle-scale lakes of our country show that the number of lakes tending eutrophication has already added up to 92%. According to the total density 0.2mg/L of nitrogen and total density 0.02mg/L of phosphorus in the world as the standard of judging of eutrophication of lake, the total nitrogen of most lakes is generally 5-12.5 times higher in density, and the total phosphorus of some lakes is 10-50 times higher in density. So, the administration of lake eutrophication has already become the hot question of the lake research field of our country, and has caused the extensive concerns of the governments at all levels of our country. Since " the Seventh Five-Year Plan Period ", the country and locality have invested a large number of financial and material resources in succession, and have carried on a series of administration technology and theoretical researches on Dian Chi Lake, TaiHu Lake, Chaohu Lake and a lot of small-scale lakes near city where the eutrophication degree is more serious, and have made some gratifying research results, which offers reference and consulting for realizing the lake ecosystem resuming. However, because of the complexity of the lake ecosystem, so far. there are no lakes realizing its reservation recovery goal. Therefore, the question of realizing the lake ecosystem resuming is a complicated systematic question, under the premise that numerous influence factors still exist, it is hard to work to take any single administration measure.The hot and difficult problems in modern ecosystem research are resuming of degradated lake ecosystems, involving numerous research fields. On the bases of consulting a large number of a large number of domestic foreign documents and drawing lessons from forefathers' research works, the paper carries on the research work of recovery of the lake ecosystem from the theory, technology and application, the main research contents include: (1) Using ecology theories, restoration ecology theories, hydrology theories and other relevant theories as guidance, and staring from degradated mechanism of lake ecosystem, the paper explains the degradating and resuming of ecosystem, and its relevant concept, intension, theory, influence factors, and expounds degradating mechanism of lake ecosystem. (2) The paper puts forward the compositions of pollution sources of the lake ecosystem, and its influence to lake ecosystem degradation; (3) The effective technology that different pollution sources controls passes through; (4) Technology integration and recovery mode that the lake ecosystem resumes; (5) Taking Tai Hu as an example, the paper systematically explains controlling technology and method to different pollution sources.Combining forefathers' research results, the paper puts forward the key technology measures about lakes ecology restoration, that is technology integration system controlling the foreign source and endogenous pollution sources at the same time. And by the mathematics means to pass relevant analysis, the paper probes into the nutrition salt in Tai Hu Lake (total phosphorus, total nitrogen), and main pollutant COD and industrial sewage emission, purse seine cultured area, quantitative relation among sink water plant distribute areas announces the main reasons that Tai Hu Lake degradates, at the same time, which Offers scientific basis for realizing the ecology resuming of Tai Hu, offers the studying direction for controlling eutrophication of the similar lakes. By investigating the scene and utilizing the water plants existing at Tai Hu Lake, the paper probes into purification functionof the wind eyes lotus and water peanut to the river; and constructs wetland lab scale systems which is formed by 10 plants such as emergent macrophytes, floating macrophytes and submersed macrophytes , etc. In addition, the paper carries on dynamic simulated test on purification function in river, and probes into purification result of plant community construction in enter water density fluctuate the under short term. The result of study indicates that it is effectual that what the plant community components in the system to get rid of nutrition thing, and can be more than 50% to lead equally. It obvious that entering water density changes influence the rate to get rid of TN, running time has great impact to get rid of TP; The system has obvious restraint function on the alga.The technical integration system suiting ecosystem resuming of Tai Hu Lake is put forward, mainly including: (1) The control technology and ways of pollution sources of Tai Hu Lake ecosystem; (2) Tai Hu Lake lakeside bring constructed wetland structure technology; (3) The ecology of Tai Hu Lake restoration technology provide the reference basis for realizing the recovery of Tai Hu Lake ecosystem; put forward the mode of Tai Hu Lake ecology restoration that ecological benefits, economic benefits combine with social benefit, namely the foreign pollution sources control mode combined with the sewage treatment plant — the leading storehouse — the constructed wetland, and based on ecological project of physics lakeside bring wetland ecology — economic mode and Tai Hu Lake some ecology of water areas— fishery's endogenous pollution sources controls the mode.The result of study indicates that the lake ecosystem degradation is a result of influencing synthetically in various kinds of factors, in which the mankind interferes is a main influence factor. So, we can promote the direction change of the development of degradation in the lake ecosystem, thus realize the goal of resuming in its ecology. The control of foreign pollution sources is the prerequisite and essential terms that realize the lake ecosystem resume. It must be under intervening artificially, promote the improvement of its elasticity and environmental capacity of the lake ecosystem are more important things. Adopting the technological measure that the foreign pollution sources controls together with endogenous pollution sources, resuming purification function of lakeside bring and resuming lake aquatic high plant community of water areas are the main technological ways of realizing degradating in the lake ecosystem.