北京市典型河湖再生水补水生态环境效应研究

【作者】 刘克；

【导师】 刘先林； 唐新明；

【作者基本信息】 首都师范大学 ， 地图学与地理信息系统， 2012， 博士

【摘要】 再生水作为一种稳定的再生水源,在维持河湖景观、恢复河湖生态等方面发挥了重要作用。然而,再生水大量补充城市河湖水体必然引起其水质水量快速变化,在高度城市化、人工化背景下对城市水环境和水生态系统产生显著影响,如植被等生物特征的改变。本文以北京市再生水补水典型河段(清河、北小河、坝河、通惠河)和湖区(奥林匹克公园)为研究对象,通过野外监测和资料分析,探讨水质时空分布和变化规律,并利用遥感技术提取地表环境信息,结合实地调查数据,研究区域发展和环境变化对水质时空变异的影响机制；在综合分析再生水补水河湖水质特征和环境背景影响因素的基础上,通过野外监测和室内控制实验,研究再生水补水与植被的相互影响关系,建立生态响应模型,揭示再生水与生态环境作用机制,据此提出北京市再生水补水河湖生态环境恢复对策。本文研究结论如下：(1)北京市社会经济发展、水资源短缺而污水处理设施建设滞后是造成城市水环境恶化的重要原因。水质监测数据时间序列分析表明：时问上,再生水补水河湖水质以2008年最优,多数再生水补水河段水质从2005年后呈明显改善趋势,主要污染物得到削减；空间上,与郊区河段相比,城区再生水补水河段水质较好,水环境质量显著提高。(2)2011年野外水质监测数据表明：再生水补水河段属于严重污染级别(劣V类)。主要超标指标为TN,是导致水质恶化的首要因子；不同河段相比,北小河水质明显劣于其他河段,通惠河水质最好,再生水补水水质和利用量是造成该结果的重要原因。再生水补水河段TN、NO2--N、NO3--N、COD、TP、NH4+-N这6个水质指标中,除TN、NO2--N外,均与季节相关性显著。采样点水质指标的空间自相关性不大,受局部控制因素影响(人为因素)。再生水排水对COD和NH4+-N含量降低有显著作用。除北小河排水口外,其他河段再生水排水口大部分水质指标较上游采样点相对较好或者基本持平,再生水的补充对河道水质有明显的改善作用。水体含氮水平、有机物水平、含磷水平、含盐水平以及不确定因子共同影响着再生水补水河段的水质。整体上,研究区水质表现为成分复杂、浓度高、人为干扰明显的特征。相比再生水补水河段,再生水补水湖泊水质较好。2010年奥林匹克公园南园湿地水质监测结果表明,除TN外,多数指标均值达到Ⅲ类地表水环境标准。各项水质指标呈现较为明显的季节变化。再生水经再生水处理区和循环湖水处理区的湿地植被和微生物作用之后到达氧化塘,水质明显改善,但是依然处于中等富营养化状态。(3)影响再生水补水河湖水质的环境背景因素除了土地利用外,还包括不透水面盖度、河道渠道化、人工闸坝等。大部分水质指标(COD、TP、TN、NO2--N)与近岸边带尺度环境背景因素的相关关系要好于其与远岸边带尺度环境背景因素的相关关系。考虑空间距离权重的影响可以增强对水质空间特征的理解。(4)奥林匹克公园南园湿地芦苇和香蒲的叶绿素含量、地上鲜生物量、全氮、全磷指标呈现明显的季节变化。氮磷含量分布的季节差异是氮素、磷素在植株内各个器官分配和转运的综合结果。芦苇和香蒲的生物量随水中营养物质含量的增加而增加,其体内氮磷含量与水体营养盐浓度存在一定的相关性,芦苇和香蒲对不同水处理区氮磷营养盐的去除发挥重要作用。不同季节和不同盖度的芦苇和香蒲冠层反射率不同,不同再生水处理区的芦苇和香蒲的反射率高低有明显差异。利用芦苇和香蒲光谱,应用多种统计回归方法预测水体TN含量和叶片TN含量,建立光谱指数模型,SMLR模型和PLSR模型3种关系模型,并通过交叉验证决定系数和均方根误差对模型精度进行检验。结果表明,同单变量回归模型相比,多变量回归模型的精度较高,其中偏最小二乘法所建模型最优。模型建立时不仅要考虑建模方法,还要兼顾植物类型和其他环境因子的综合影响。(5)利用水培芦苇进行氮的室内控制实验。不同N浓度处理下,随着N浓度的升高,芦苇高度、叶绿素含量、各器官生物量和N贮量均呈现上升趋势,有效N的增加促进了各器官生物量的积累。根系N浓度和叶片N浓度具有显著相关关系。不同N营养水平芦苇光谱原始反射率和一阶导数在可见光波段和红边区域有明显表现,且不同N梯度的光谱存在一定的差异,这与N影响下的芦苇叶绿素含量水平不同有关。PRI和CI指数是建立植物光谱与N梯度关系以及植物光谱与理化参数关系的良好高光谱指数形式。通过以上研究结论提出：加快再生水处理厂建设,保证再生水出水水质,加大再生水回用量,降低人为因素的负面影响,建立良好的植物水质净化体系,发挥遥感优势,加强监测与管理是北京市再生水补水河湖生态环境恢复的有效途径。本文研究成果能够为再生水补水河湖的监测、管理以及生态恢复提供一定的科学依据和参考借鉴。更多还原

【Abstract】 Supplying urban rivers and lakes with reclaimed water is recognized as a superior way for ecological restoration and reconstruction. However, tremendous supplement of reclaimed water will bring intense influence to water quality and quantity. Simultaneously, intensive human activities remarkablely influence urban hydrology, water environment and environmental system, such as changes of biology characteristics. We select typical rivers (Qing river, Beixiao river, Ba river, Tonghui river) and a lake (Olympic Park) supplied by recycled water in Beijing as our study areas. The spatial and temporal variations of water quality are investigated through field work; the influence mechanism of social development and environmental change on water environment are researched combined with a variety of surface environmental information. Based on the comprehensive analysis of water quality characteristics and environmental background, we study the characteristics of reclaimed water and vegetation, and thus establish the eco-environment response models to reveal the interaction mechanisms between recycled water and ecological environment. The environment recovery countermeasures for rivers and lakes using reclaimed water in Beijing are proposed in this study. The conclusions are demonstrated as follows:1) Water resource shortages and backward construction of sewage treatment facilities are important reasons for water environment deterioration in Beijing. It can be seen the best water quality of rivers and lakes supplied by reclaimed water in2008; The water quality have been significant improved from2005; the construction of the sewage/water recycling plants is of great importance to water environment amelioration.2) The rivers are all heavily polluted (inferior Class Ⅴ of Environmental quality standards for surface water). The main indicator exceeding the criterion is total nitrogen (TN), which is the primary factor leading to the deterioration of water quality. The water quality of Beixiao river is distinctly worse than the other three rivers, while Tonghui river possesses the best water quality. There is an evident correlation between water quality and seasons except TN and NO2--N. Spatial autocorrelation of water quality indicators is weak, which means they are subject to human activities. The reclaimed water drainage has a distinct effect on reducing COD and NH4+-N content. Majority of water quality values from outfalls in the rivers except for Beixiao river are relatively lower than or basically coincident to that in the up streams. The water quality could be obviously advanced when supplying recycled water to rivers. The nitrogen, organic matter, phosphorus and salinity content, together with uncertainty factors, severely affect the water quality of rivers supplemented by reclaimed water. The water quality in the study is depicted by complex components, high concentrations and intensive anthropogenic interference. The water quality of the recycled water in Olympic Park is much better in comparison with the reclaimed water supplied rivers. However, some indicators, such as TN, TP, beyond the surface water environmental quality standards Grade Ⅲ. Various water quality data show obvious seasonal variations. Water quality of recycled water is improved significantly after the reclaimed water interacts with the wetland vegetation and microorganisms in the water treatment area and circular lake handling area. Nevertheless, it is still in a moderate eutrophication.3) The environmental background factors influencing reclaimed water quality in rivers involve land use, impervious surface coverage, floodgates and dams, river vulcanized and so on. Most of the water quality indicators (COD, TP, TN and N02--N) exhibited stronger relationship with environmental background factors in the near-shore scale compared with far-shore scale. Considering the spatial impact can enhance the comprehension of the spatial characteristics of water quality.4) The physical and chemical parameters of reed(Phragmites australis) and cattail (Typha angustifolia), including chlorophyll content, ground fresh biomass, total nitrogen content, and total phosphorus content, denote distinct seasonal variations. The seasonal differences of nitrogen and phosphorus content are due to allocation and transport of nitrogen, phosphorus in various organs. Most high values of the physical and chemical indicators of Phragmites australis and Typha angustifolia appear in the circular water treatment area. Phragmites australis and Typha angustifolia biomass are increased by higher nutrition availability in the water, and the overall correlation between nitrogen, phosphorus content of the two species and nutrition in water is obvious. Phragmites australis and Typha angustifolia play an important role in removal of nitrogen and phosphorus. The canopy reflectance of Phragmites australis or Typha angustifolia changes with seasons or coverage. The difference of Phragmites australis or Typha angustifolia reflectance is distinct among reclaimed water treatment areas. The research establishes univariate models involving simple ratio spectral index (SR) model and normalized difference spectral index (ND) model, as well as multivariate models including stepwise multiple linear regression (SMLR) model and partial least squares regression (PLSR) model using the reflectance of Phragmites australis and Typha angustifolia to predict the TN in water and leaves. Moreover, the accuracy of all the models was tested through cross-validated coefficient of determination (R2cv) and cross-validated root mean square error (RMSEcv). The results showed that compared different types of wetland plants, the accuracy of all established prediction models using Phragmites australis reflectance spectra was higher than that using Typha angustifolia reflectance spectra. Compared with univariate techniques, multivariate regressions improved the estimation of TN concentration in water and leaves. Among the various investigated models, the accuracy of PLSR model was the highest. Other environmental factors should also be discreetly considered in modeling exercise.5) Phragmites australis are used to conduct the control experiment. The nitrogen treatment are0,1,2,5,20mg/L. Height, chlorophyll content, biomass, and N concentration of Phragmites australis all illustrate a rising trend with increasing N concentration. The increase of available N promotes the biomass accumulation for each organ. N concentration in root and leaf display a positive relationship. Reflect spectra and1st spectra of Phragmites australis across five fertilization levels have evident performance in the visible and red edge regions; the differences of the reflectance show the effect of N treatment concentration. PRI and CI are most optimal indices to establish the relation between Phragmites australis spectra and N treatment levels, also the relationship between Phragmites australis spectra and chlorophyll content.According to the results mentioned above, we propose that:speed up the construction of recycled water treatment plants, increase the reuse of wastewater reclamation, decrease the negative influence of human beings, establish a favorable plant water purification system, make full use of remote sensing to strengthen monitoring and management are effective ways to restore ecological environment of reclaimed water replenishment rivers and lakes in Beijing. The research results from this study can provide a strong scientific basis for monitoring, management and ecological recovery of lakes and rivers using recycled water.更多还原