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题名: 水陆交错界面氧化还原状况变化特征与氨氮吸附机理
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.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/36805
Appears in Collections:环境水质学国家重点实验室_学位论文

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Recommended Citation:
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.
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