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Shallow lake and reservoir sediment - water interface nitrogen, phosphorus migration and transformation kinetics model simulation and experiment

Author: SongXueLi
Tutor: XueChuanDong
School: Kunming University of Science and Technology
Course: Geological Engineering
Keywords: Shallow-type lake and reservoir Modern sedimentary-water interface Nutritive material Migration modle of TP "3N" model of migration and transformation Dianchi lake
CLC: X524
Type: Master's thesis
Year: 2009
Downloads: 257
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Abstract

With the development of economic and urbanization, hydrochemical pollution and eutrophication of the shallow-type lake and reservoir becomes more and more serious.The import and beneficiation of the nutritive material such as nitrogen and phosphorus, is the fundamental reason of eutrophication and phytoplankton bloom of the water. Modern sedimentary is the main carrier of the nutritive material in the eutrophia water substance, and the releasing of these make the problem of the eutrophication more serious. Modern sedimentary-water interface is one of the most important interfaces in the lake and reservoir, nourishment material transferring between modern sedimentary and waterbody is the important approach of the endogenous capacity release in the substrate sludge and the accumulation of nourishment material in the water.Research of the vertical circulation of biogenic elements like nitrogen andphosphorus,and the diffusion, inversion and migration in vertical circulation of vital factors like nitrogen, phosphorus etc. is the key to understand the migration and transformation laws of nitrogen and phosphorus between modern sedimentary and water and the conversion mechanism of endogenous nutrients in the shallow-type lake and reservoir. And the results can provide a series of primary data and scientific principle for the eutrophication control and comprehensive management of lake and reservoir.As a case to Dianchi Lake, sampling in the typical eutrophic shallow-type-lake and reservoir(water sample 500 litre, modern sedimentary sample 40 kilogram),using the PVC bucket and the bucket made of plastic as the analog device, indoor simulation experiment—sedimentation experiment of nitrogen, phosphorus in water substance, diffusion experiment of nitrogen, phosphorus in modern sedimentary, pH vable of nitrogen and phosphorus migration. A series of migration and transformation laws about various forms of nitrogen and phosphorus has been provided. Based on the comprehensive studying, the results obtained is listed as follows:Firstly, tested 2292 simples altogether,the simple of consistency on TN, NO3--N, NO2--N, NH4+-N, TP, DP in water has 352 pieces each and the simple of consistency on TN, TP in modern sedimentary has 90 pieces each. Secondly, in the study area, concentration of the nitrogen and phosphorus far beyond the critical value of eutrophication. Nitrogen and phosphorus in the modern sedimentary has a clear "source/sink" conversion,and changes energy and matter with the water.Thirdly, modern sedimentary is the carrier of NH4+-N in water substance.When oxygen is sufficient, organic nitrogen content of modern sedimentary generate NH4+-N and other inorganic ion diffusion into the overlying water, nitrifying bacteria translate the NH4+-N into NOO--N by nitration, part into NO2--N, ultimately translated into NO3-N. Insufficient oxygen in the water substance, inhibiting the occurrence of nitrification, N in the overlying water mainly existed in the form of NH4+-N. When water depth in the same conditions,the greater thickness of substrate sludge is, the greater concentration of NO2--N、H4+-N、TP、DP in overlying water becomes. Under the acidic conditions, nitrification was inhibited, the N in water in the form of NH4+-N, yet P is not affected. In alkaline conditions, the release action of P in modern sedimentary and the deposition of P in the water that reaches a certain concentration are very strong, and all the forms of N are not affected. In alkalescent environment, NH4+-N turns to NO2--N by nitrification,and NO3--N turns to NO2--N by denitrification.Fourthly, on the basis of obtainning various parameter of nitrogen, phosphorus conversion from the experimental data(including rate parameters of the transformation of nitrogen, sedimentation and release coefficient of phosphorus), the one-dimensional TP models of TP concentration in the different depth of water change over time, and the one-dimensional "3N" (NH4+-N、NO3--N、NO2--N) model of migration and transformation is established. Then, applying the simulation experiment data to the model, the compatibility of the trend of the migration and transformation of "3N" and the theoretical calculation curve of first-order chemical dynamic equation is gained. Using the migaration model of TP to the Dianchi lake, and comparing with the monitoring data of the monitoring points in 2003, it is showed that there be little difference between them.Lastly, the simulation experimental process of the transformation and migration of nitrogen and phosphorus between modern sedimentary and waterbody, and the detailed methods and techniques established in this thesis can be used to the similar research field. At the same time, a large number of experimental data can also be refered to other related experiments. The dynamics simulation model could be used to forecasting the consistency trends and migration laws of nitrogen and phosphorus in the eutrophia water of Dianchi lake and similar shallow-type lake and reservoir.

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CLC: > Environmental science, safety science > Environmental pollution and its prevention > Water pollution and its control > Lakes and reservoirs
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