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三峡库区支流消落带泥沙沉积的时空特征及物源研究
Alternative TitleTracing sediment in the riparian zone from the tributary of the Yangtze River in the Three Gorges Reservoir
王永艳
Subtype博士
Thesis Advisor文安邦
2017
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline土壤学
Keyword泥沙沉积 泥沙物源 支流消落带 三峡水库
Abstract三峡水库水位为满足发电需求每年10月底蓄水至175 m,为了防洪6月初落至145 m,这种独特的运行调度形成了垂直高差达30 m的水库消落带。受坡面径流、水动力条件以及反季节淹没出露等影响,三峡水库消落区存在大量淤积泥沙,目前已经引起生物多样性丧失、养分元素的富集以及重金属污染等诸多生态环境问题。同时,由于长江上游水库群的投入使用导致上游入库泥沙减少,库区坡面侵蚀产沙增加,从而导致入库泥沙的来源发生变化。同时,支流受干流顶托的作用,大量次级支流淤积河段出现水体富营养化现象。基于以上背景,以野外台站观测数据为依托,采用野外调查采样与定位观测相结合,本文拟查明支流消落带泥沙从库区上游到下游的空间变化特征以及不同高程带的泥沙沉积特征,摸清不同物源对支流不同高程带消落带泥沙的相对贡献,为消落带营养元素迁移过程及消落带生态环境修复研究提供基础依据。本研究取得了以下结果:(1)三峡水库支流消落带沉积泥沙理化特征在水平、高程和沿程三个维度均存在空间差异。首先,三峡水库沿水流方向由上游至下游,各支流消落带泥沙颗粒呈现先变细后变粗的特征,中值粒径d50的变化范围为8.76~17.94 μm,沉积泥沙的中值粒径最小值出现在汝溪河,最大值出现在龙河。各支流采样点的TOC含量呈现波动趋势,TN和TP的含量沿水流方向均表现为局部波动整体升高的趋势,具体表现为库尾含量低,库中和库首含量较高。第二,各支流165-175 m高程带粒径比145-155、155-165m高程的沉积泥沙颗粒偏粗,单因素方差分析表明三峡水库反季节蓄水形成高程达30m变幅的消落带由于受人为干扰等因为并未导致沉积泥沙的TOC、TN、TP等养分元素在不同海拔高程间的明显差异。第三,汝溪河和彭溪河消落带沿程沉积泥沙随着距河口距离的变化,理化特征均呈现不规律的变化特征,说明受干流来水来沙的影响范围和作用机制存在空间变异性,同时受人类扰动作用和河流流速影响造成沉积泥沙特征的沿程差异性。(2)干支流悬移泥沙吸附的TOC和TN在研究时段内随月份表现出相似的变化趋势,干支流悬移泥沙吸附的TOC和TN的最大值都出现在2016年3月。然而,干流悬移泥沙的TP含量的最大值出现在2015年9月,而支流出现在2016年3月。支流悬移泥沙的TOC、TN和TP浓度全部高于干流,其中支流悬移泥沙TOC、TN含量约是干流的4倍。干流和支流悬移泥沙137Cs比活度在旱季和雨季差异性显著,变异系数分别为57.5%和158.4%。汝溪河消落带年沉积泥沙量表现为随着距河口距离的减小而增大,同时随高程的增加而减少,145-155m、155-165m和165-175m高程带泥沙沉积量的平均值分别为8.66、6.76和3.63 kg/m2。淹水是支流消落带发生泥沙沉积的重要前提条件,而不同高程带淹水强度、周期和频率的差异决定了泥沙沉积率的差异。(3)根据沉积泥沙137Cs、粒度和有机质的季节性旋回分布特征,确定泥沙沉积季节,进而估算沉积年代,初步建立三峡水库消落带泥沙沉积过程。物源输入通量在三峡水库干流和支流间存在显著差异,汇合口消落带的泥沙沉积速率为16 cm/yr,而支流汝溪河库湾消落带则仅为10 mm/yr。干流雨季的悬移泥沙经过长距离的泥沙搬运造成库区中部细颗粒泥沙的富集;旱季则主要来自于由船行波导致的库岸侵蚀。而对于支流消落带沉积泥沙来说,雨季悬移泥沙主要来源于流域上游暴雨事件造成的坡面侵蚀产沙,旱季的悬移泥沙主要来源于干流来沙。(4)本文将泥沙来源复合“指纹”示踪技术的最新方法运用到三峡水库支流典型消落带沉积泥沙物源示踪研究中,将支流消落带沉积泥沙的物源划分为3类,包括长江干流、支流上游和库岸侵蚀,分别统计筛选出不同高程带具有诊断能力的指纹因子组合,其中145-155 m、155-165 m和165-175 m高程带最具判别能力的组合因子分别是Na、Pb、Mg、Ca、Mn,Pb、Mg、Ca、Mn,和TN、Ca、Mn。运用混合模型估算出长江干流、支流上游和库岸侵蚀对不同高程带沉积泥沙的贡献率分别为145-155 m:73.2%、26.8%、0,155-165 m:72.6%、27.4%、0,165-175 m:57.3%、39.7%、2.98%。
Other AbstractThe Three Gorges reservoir adopted a special operational strategy which was impounded to a maximum water level of 175m during the dry season (mainly October to February) for energy generation and discharges to a base water level of 145 m during the rainy season (mainly June to Autumn) for flood control. Operation of this unique form of WLFZ reservoir was 30m. Thus created a water-level fluctuating zone with a vertical height of 30 m. Affected by the slope runoff, hydrodynamic conditions and seasonal submerging and exposing, there are a lot of silt in the riparian zone of Three Gorges Reservoir at present, and has caused the loss of biodiversity, many environmental problems of nutrient enrichment and heavy metal pollution. At the same time, giant dams constructed on the Upper Yangtze River mainstream and tributaries reduced total suspended sediment load transported to TGR, and reservoir regional sediment yield increased, resulting from sediment sources changed. Tributaries were affected by the backwater from Yangtze mainstream, a large number of tributaries appeared phenomenon of eutrophication. Based on the above background, based on the observation data of field stations and combining with the field sampling, this study intends to carry out research on typical tributaries in TGR, ascertain the temporal and spatial variation characteristics of deposited sediments in tributaries WLF zone from upstream to downstream of the reservoir and vertical direction, preliminarily revealed the sedimentation processes and source composition of sediment in the riparian zone of a typical tributary from the Three Gorges Reservoir. This study afforded an important practical and scientific basis for migration process with nutrients down and ecological environment restoration research. The following principal conclusions were obtained:(1) There are spatial differences of sedimentary sediments characteristics from WLFZ of Three Gorges reservoir at level, elevation and along flow direction dimensions. Firstly, the median diameter (d50) of deposited sediments from tributaries range between 8.76~17.94 along the flow direction of the Three Gorges Reservoir ,the minimum median diameter of sediment in Ruxi River and the maximum value appeared in the Long River. TOC of sampling point from tributaries content have a fluctuated trend, variations of TN and TP content were similar with TOC, both show like fluctuating local and increase in the overall trend. Secondly, particle size of upper elevation (165-175m) were coarser than that from lower elevation (145-155m) sediment. Thirdly, Ruxi River and Pengxi River riparian zone along the flow direction, with the change of distance from the river mouth, physicochemical characteristics varied, it may imply there are spatial variability of the effect and mechanism from Yangtze mainstream.(2) Total organic carbon (TOC) and total nitrogen (TN) of suspended sediments from both Yangtze mainstream and tributary have similar temporal variation. The tributary suspended sediments exhibited seasonal particle size variability, whereas the Yangtze mainstream did not. Concentrations of TOC and TN were notably higher in the tributary than those in the Yangtze mainstream and the highest values associated with the tributary suspended sediment were measured in March 2016 due to the slow flow pattern associated with the full impoundment of the TGR, suitable meteorological conditions. The mainstream and tributaries of the suspended sediment 137Cs activity significantly in dry season and rainy season difference, the coefficients of variation were 57.5% and 158.4%. Deposited sediment amounts in the sampling sites of riparian zone in the Ruxi River showed clear t spatial variations, reduce with the elevation increasing, and average sediment deposition amounts of 145-155m, 155 -165m and 165-175m were 8.66,6.76 and 3.63 kg/m2. Flooding is an important premise condition for sediment deposition in WLFZ of the tributary. The difference of induration intensity and frequency at different elevation determines the rate of sediment deposition. Sediment deposition in tributary show elevation difference characteristics as a result of TGR regulation and seasonal suspended sediment. The sediment deposition of lower elevation (mainly in the summer floods below) mainly comes from upstream watershed sediment and suspended sediment in the upper reaches, and the main source of higher elevation is the suspended sediment from the upper reaches of Yangtze River.(3) According to the 137Cs activity, seasonal characteristics of grain size and organic matter distribution of the sediment in the profile from the zone of Three Gorges reservoir, preliminary cycle identification method of sediment seasonal drawdown is established. The confluence of riparian zone sediment deposition rate was 16 cm/yr, while the tributary river riparian of Ruxi bay was only 10 mm/yr. The sedimentation rate in the WLFZ of Yangtze mainstream was significantly greater than the tributary as a result of significant differences in the source input flux in the mainstream and tributaries of the Three Gorges reservoir. The finer suspended sediment had an enrichment in the central reservoir after long distance sediment transportation in rainy season. Suspended sediment mainly originated from bank erosion caused by the ship wave dry season. However, for the tributary, suspended sediment mainly obtained from the upstream watershed caused by rainstorm events during the rainy season, and the suspended sediment from Yangtze mainstream was the main contributor during the dry season. (4) According to the sediment source composite fingerprinting approaches, three potential sediment source groups were identified as sediment yields from upstream of Yangtze mainstream, sediment production from upstream of local catchments and sediment export from bank erosion in the riparian zone of tributary. A composite of sediment fingerprints of Na、Pb、Mg、Ca、Mn (145-155 m);Pb、Mg、Ca、Mn (155-165 m), and TN、Ca、Mn (165-175 m) were further identified using statistical analysis and the relative contributions of individual sources to sediment in the riparian zone along the Ruxi tributary of the Three Gorges Reservoir were finally estimated. Finally, Yangtze mainstream, upstream of local watershed and bank erosion on different elevation sediment contribution rate were 73.2%、26.8%、0 at elevation of 145-155 m; 72.6%、27.4%、0 at elevation of 155-165 m; 57.3%、 27.4%、39.7%、2.98% at elevation of 165-175 m. 
Pages99
Language中文
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/24589
Collection山地表生过程与生态调控重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
First Author Affilication中国科学院水利部成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
王永艳. 三峡库区支流消落带泥沙沉积的时空特征及物源研究[D]. 北京. 中国科学院大学,2017.
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