水陆交错界面氧化还原状况变化特征与氨氮吸附机理
文献类型：学位论文
| 作者 | 黄维 |
| 学位类别 | 硕士 |
| 答辩日期 | 2016-06 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 王为东 |
| 关键词 | Wetlands, Ecotones, Oxidation-Reduction (Redox), Ammonia Nitrogen, Adsorption, Interaction of River and Lake, Water Level Fluctuation |
| 其他题名 | Variation Characteristics of Redox Conditions and Mechanisms of Ammonia Nitrogen Adsorption at the Terrestrial-Aquatic Interfaces |
| 学位专业 | 环境工程 |
| 英文摘要 | Wetland ecosystem is one of the most important ecosystems on the Earth, which plays a key role in the biogeochemical cycle and ecological environment protection. The land/water ecotone is the core of the wetland, and it is the interface area between the aquat-ic ecosystem and the terrestrial ecosystem. Soil at the interface area provides the medium for organism growth, the water level fluctuations are accompanied by the supply of nu- trients, the air provides the oxygen required, so the interface is the intersection of water,gas and soil. The ecotone possesses higher biological species and rhizosphere microbial activity. Pollutants from runoff are mostly intercepted, filtered and degraded in this environment, especially the water fluctuation providing an alternation of aerobic and anoxic environment as well as suitable conditions for the microbial community. The land/water ecotones are also the regions supporting the strongest reduction and oxidation (redox) reaction. In all, land/inland water ecotone is the “hot spots” for transfer, transformation and removal of various pollutants. In this paper, it was firstly intended to investigate the general laws of water chemistry, hydrology and other eco-environmental variations between river and lake through the case study of Chaohu Lake-Tongyang River and Dongting Lake-Yangtze River. Secondly, through the research of redox conditions and gradient variation in the plant-bed/ditch system of Shijiuyang wetland, we want to make the pollutant removal mechanisms clear. On the basis of above research, thirdly, by further focusing on the ammonia nitrogen removal using a wide range of matrices and soils, the mechanism of ammonia nitrogen removal was examined and the capability of soil retention on ammonia nitrogen in different regions of reed wetland was analyzed. The overall objective is to probe into the interaction between lake and river, to explain the removal mechanism of pollutants, especially for ammonia nitrogen, thus providing some technical support for the restoration of riparian zones, and furnishing a new theoretical guidance for the construction and operation of constructed wetlands. The experimental results and the major findings are summarized as follows: 1. A case study of Dongting Lake-Yangtze River. The Three Gorges Dam Project(TGP) on the Yangtze River is the world’s largest hydropower complex project. Dongting Lake is the first large lake downstream of the TGP, and substantial changes have been noted in the hydrological regimes, water quality, and wetlands environments since the TGP began operation. This review summarizes the influence of the TGP on Dongting Lake based on the reservoir dispatch scheme, interaction between the river and lake, and vegetation distribution patterns of lake wetlands. The TGP reduced the sediment discharge from the Yangtze River to Dongting Lake and slowed the sediment deposition rate. This was beneficial for the lake in the short term because it increased the water regulation space and extended the life of Dongting Lake. The TGP reduced water inflow from upstream and changed the variation pattern in water level. The TGP exerted direct and indirect effects on water quality of Dongting Lake. There are still controversies regarding water quality impacts of the TGP operation on Dongting Lake, and the TGP has exacerbated pollution in some regions. Reduced water level variation and sedimentation have jointly changed the process of vegetation succession in Dongting Lake. The succession rate becomes slow,and the vegetation succession sequence is aquatic plants, Phalaris arundinacea or Carex sp., Phragmites australis, and ligneous plants. 2. A case study of Chaohu Lake-Tongyang River. This chapter reported the spatial distribution characteristics of major nutrients (N, P) and chemical oxygen demand (CODCr) in Tongyang River flowing into Chaohu Lake. We adopted a comprehensive evaluation system based on principal component analysis (PCA) of multiple indices to characterize the spatial variation trend of river water quality. The water quality of three sections of Tongyang River was influenced by both human activities in the river basin and the riverine self-purification function. PCA analysis used to compare the loading of water quality indices indicated that N and P were the key controlling factors. The first principal component named as nitrogen and phosphorus nutrients factor explained about 60% of the spatial variation of river water quality. The second principal component named nitrification potential and organic pollution factor explained 30% of the spatial variation of river water quality. The results show that river is the most important channel connected the lakes and waters. The pollution prevention and terminal control of river basin is particularly important. Therefore, it is necessary to implement high amplitude load reduction and pollution control of Tongyang River, which is a major source of pollution (rural sewage,industrial effluent, solid waste and agricultural non-point source pollution, etc.). 3. Shijiuyang wetland in Jiaxing is a large-scale nature imitated ecological wetland originating from the natural prototype of reed-dominated wetland in Baiyangdian Lake.This chapter studied the mechanism of redox condition and material retention process for various substances in different interface regions, including rhizosphere and non-rhizosphere,surface and subsurface. Root surface is a special and typical interface, where oxygen in the atmosphere could transport continuously because of well-developed aerenchyma, forming micro aerobic area around. It was found that the urease activity in the rhizosphere was signigicantly higher than that in the non-rhizosphere, the Fe2+sphere was 27.5–465.7 mg/kg, while the corresponding Fe2+concentration in the rhizoin the non-rhizosphere was 0.1–1.0 mg/kg. In the presence of organic acids, complexation can significantly improve soil soluble iron concentration. Microorganisms in the rhizosphere consume a lot of oxygen, increasing the concentration of carbon dioxide, and therefore affect the oxidationreduction potential and pH value, promoting the reduction and uptake of Fe3+。 Urease activity, organic matter, ammonia nitrogen and nitrate nitrogen contents in the surface layer of wetland soil was significantly higher than those in the subsurface. This was due to the fact that the litter accumulation which leads to very high organic matter content. The urease activity increased accordingly. Mineralization of organic matter results in the high content of ammonia nitrogen, and ammonia nitrogen converted into nitrate due to nitrification and raised the nitrate nitrogen level. In a word, there are many interfacial areas inside the wetland system, such as rhizosphere and non-rhizosphere, surface and subsurface, which play a key role in the transformation and degradation of pollutants. 4. At present, the nitrogen pollution in our country is becoming more and more serious. Riparian zone as an important land-water interface plays a very important role in the interception of non-point source pollution. The final elimination of ammonia nitrogen is through the microbial nitrification-denitrification and anaerobic ammonium oxidation.While the primary rate limiting step is adsorption and enrichment of ammonia nitrogen.We carried out indoor model simulation experiments, using different kinds of matrices such as zeolite, gravel, volcanic rock, calcite, activated carbon and so on. Except activated carbon, we found that the larger the specific surface area, the stronger the absorption capacity. Activated carbon does not have sufficient adsorption capacity for ammonia because it usually possesses a non-polar surface, and there is also not exchangeable ions.Then we collected soils from representative reed wetlands in our country and compared the adsorption capacity of soil and stone. It was found that at room temperature, the adsorption performance of zeolite on ammonia nitrogen (9380 mg/kg) was significantly higher than that of the soil (500–1500 mg/kg) and other stone materials, which can be used as an important material for the removal of ammonia nitrogen. Further study found that the variation trends of ammonia adsorption capacity of zeolite and soil with temperature are not the same. The adsorption capacity of zeolite decreased as temperature decreased,while that of soil stayed stable as temperature decreased. This is mainly due to the different adsorption mechanism of zeolite and soil. Ion exchange was the main mechanism of ammonium adsorption for zeolite, while the adsorption of ammonia in soils was the combined results of ion exchange and adsorption. And the adsorption capacity of soils varied significantly in different places. The BET specific surface area, cation exchange capacity, ratio of Si/Al and salinity were the key factors to determine the adsorption capacity. The contribution of soil organic matter and minerals to the adsorption is distinct.Organic matter contributed much more on ammonia nitrogen adsorption than minerals. In addition, climate and weathering degree may be the external factors determining different adsorption capacity at different places. |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/36805]  |
| 专题 | 生态环境研究中心_环境水质学国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 黄维. 水陆交错界面氧化还原状况变化特征与氨氮吸附机理[D]. 北京. 中国科学院研究生院. 2016. |
入库方式： OAI收割
来源：生态环境研究中心
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