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1.
对太湖西北部主要入湖河流、河口及近岸湖区64个表层沉积物样品进行粒度分析,结合粒度参数计算和聚类分析,探讨了表层沉积物的粒度分布特征及其沉积类型.研究结果表明:研究区沉积物平均粒径介于4.0~58.7μm之间,粒级组分为黏土、粉砂和砂,其含量的均值分别为7.19%、81.81%和11.00%.太湖西北部表层沉积物以粉砂和砂质粉砂为主;研究区粒度总体呈南粗北细的分布特征,太湖西部沿岸区距离物源区较近且水动力条件复杂,沉积物粒度较粗.太湖北部入湖河流沉积物的频率曲线峰形较宽,峰值位于细粒级;西岸入湖河道多呈单峰态,粒径偏粗;河口区沉积物粒径较河道偏粗,粗颗粒含量高.Q型聚类分析结果表明,研究区可分为4类沉积区,其中3类沉积区有典型特征:第1类沉积区主要分布在太湖西部沿岸,其沉积物粒度相对较粗;第2类沉积区主要位于入湖河流河口,沉积物粒度最粗;第3类沉积区位于蓝藻频发的梁溪河,其沉积物黏土含量极高,表明沉积物粒度特征可能与污染状况有一定的联系. 相似文献
2.
梯级筑坝对黑河水质时空分布特征的影响 总被引：1，自引：0，他引：1
为探究梯级大坝建设对河流水质变化规律的影响,将黑河上中游划分为坝上河段、坝下河段及自然河段,于2017年12月-2018年8月选取了24个主要控制断面进行水质调查,并采用多元统计的方法对比分析了不同时空尺度上的水质分布特征.结果表明:黑河上中游水质时空变化的主要影响因子为水温(WT)、pH值、溶解氧(DO)、电导率(EC)、总氮(TN)、总磷(TP)和五日生化需氧量(BOD_5).空间尺度上,WT、EC、BOD_5、高锰酸盐指数(CODMn)、TN等指标具有显著性差异,其中坝上河段受BOD_5、CODMn影响较大,自然河段WT、EC和TN为关键指标,而各个因子对坝下河段水质影响较小.时间尺度上,WT、EC、BOD_5、氨氮与季节变化存在明显相关性,是不同河段水质时间变化的控制因子,且大多数水质因子在非汛期变化最明显.降水、温度、水文条件等季节性影响因素和梯级水库联合运用模式是该区域水质时间差异的主要原因;空间差异主要受祁连、张掖地区外源性污染物排放以及筑坝环境下水动力条件改变而产生的沉积滞留效应和沿程累积效应影响.研究表明,外源性污染源依然是导致水质变差的主要因素,梯级筑坝则是导致水质变差的间接因素.因此控制该区域人类活动所造成的外源性污染源,并针对不同种类污染物的季节变化特征实施合理的水库运行方式是改善水电梯级开发河段水质状况的关键. 相似文献
3.
金沙江下游4个梯级水电站总装机容量相当于两座三峡水库,是“西电东送”中部地区的源头工程,工程效益发挥对经济社会发展意义重大。2012年以来,向家坝、溪洛渡、乌东德和白鹤滩电站等陆续蓄水运行,层层拦截金沙江的泥沙,2013—2020年向家坝出库年输沙量均值下降至152万t,减幅超过99%。大量泥沙淤积在梯级水库内,同时向家坝以下河道发生长距离冲刷。本文以自金沙江下游工程筹建以来的观测资料为基础,针对梯级水库的泥沙淤积和坝下游河道冲刷规律开展研究,结果表明:金沙江下游四个梯级电站自建成运行至2020年底,累计淤积泥沙约5.98亿m3,其中溪洛渡库区淤积量占比达92.5%,2013-2020年溪洛渡和向家坝水库排沙比分别为2.64%和22.2%,其水库泥沙主要淤积在常年回水区的干流河道内,以死库容内淤积为主,侵占有效库容的比例小于1.3%。金沙江下游库区干流河道的峡谷特征明显,淤积多表现为主河槽的平铺式淤高。溪洛渡和向家坝库区淤积的泥沙沿程分选特征明显,越靠近坝前,中数粒径减小、细颗粒泥沙沙量百分数增加,极细颗粒泥沙会在库区一定范围内大量沉积。向家坝下游河床普遍冲刷,但... 相似文献
4.
梯级筑坝对河流水环境演化的影响是国内外关注的热点.小型山区河流高密度梯级开发对水体生源要素的空间格局以及水环境演化的累积影响特征尚不清楚.以重庆市五布河为研究对象，对流域内8个“河流-水库-下泄水”交替系统中表层水体理化因子及碳（C）、氮（N）、磷（P）形态组成进行季节性监测，探讨了梯级筑坝对小型河流生源要素空间格局及水体富营养化风险影响的累积特征及驱动机制.结果表明：梯级水电开发对五布河流域水生生境和生源要素空间分配的影响具有潜在的累积效应，各库区水体碳氮磷浓度均呈逐级增加的空间规律；水库段的有机碳及不同形态的氮、磷浓度均高于入库河流，因此水体养分浓度呈现出河段尺度（即单个河流-水库-下泄水系统）和流域尺度（即上游至下游）耦合的空间变异模式.上游水库中溶解性氮、磷的再释放及下泄输移能够补给下游库区，加之下游水库泥沙对氮、磷的吸附-沉积作用的减弱，导致水体氮、磷总量及溶解性氮、磷的占比沿程增加，呈现梯级筑坝对水环境演化的累积影响.梯级筑坝影响下河流碳氮磷总量的相关性减弱，而溶解性养分间的相关性增强，形成了特殊的养分协同演化；水库群之间水力滞留时间的差异与水体碳氮磷浓度具有较好的线性关系，是影响流域养分分配的关键因素.五布河流域水体均为高富营养化风险，由于梯级筑坝下水体溶解性养分的逐级增加，下游水库水华风险更大；水力滞留时间与水体富营养化指数及叶绿素a浓度呈显著正向关，结合氮磷比特征的分析，本研究认为外源磷输入控制及水力滞留时间的调节是五布河梯级水库富营养化防控的有效途径. 相似文献
5.
南黄海表层沉积物粒度端元反演及其对沉积动力环境的指示意义 总被引：2，自引：0，他引：2
《中国科学:地球科学》2015,(10)
应用端元分析模型对南黄海表层沉积物粒度数据进行了反演,分离出四个端元.根据各端元频率分布曲线及平面分布特征,结合南黄海沉积动力格局,分析了各端元与研究区物源和水动力环境的对应关系.端元1和端元2反映了海洋动力过程对陆源沉积物的输运和分选,端元3和端元4反映了海洋动力对残留砂的改造.南黄海海洋锋面主要对陆源较粗颗粒沉积物的输运有影响,陆源较粗颗粒沉积物基本不能跨越山东外海海洋锋面.陆源细颗粒沉积物受海洋锋面影响较小,并在潮汐动力条件较弱的南黄海中部大量沉降,构成南黄海中部泥质区主体.南黄海中部细颗粒沉积物可能有西北和西南两个不同物源方向,其北部沉积物主要来自沿岸流输运跨越锋面后的黄河沉积物的细颗粒部分,西南部沉积物主要来自跨越苏北海洋锋面具有长江和黄河混合物源的苏北沿岸沉积物的细颗粒部分.和直接利用沉积物粒度数据研究沉积动力环境的传统方法相比,利用沉积物粒度端元分析方法分离出的沉积物不同端元分析区域沉积动力环境效果更好. 相似文献
6.
三峡水库举世瞩目,是长江保护与治理的关键性枢纽工程,水库自2003年蓄水运行后库区水沙条件均发生了显著改变,对库区水生态环境产生了深远影响。本文系统综述了三峡水库蓄水运行后库区的水流动力特性和泥沙淤积特性,总结了蓄水后水库的新水沙运动情况;从水库蓄水运行后水质参数特征,营养物质、重金属和典型有毒有机污染物的赋存特征等方面,分析了三峡水库库区新水沙变化条件下的水环境响应特征;基于水库蓄水前后浮游植物、底栖动物等重点生物群落的现存量和群落特征变化规律,探索了三峡水库新水沙变化条件下库区的水生态响应特征;最后对未来三峡水库运行下的水生态环境效应研究提出展望,本文可为三峡水库水生态环境保护科学研究和管理提供新的认识和决策参考。 相似文献
7.
石梁河水库是江苏省最大的人工湖泊.开展水库沉积速率研究,对认识水库环境变化具有重要意义.本文对石梁河水库沉积物岩芯粒度组成特征进行了分析,表明沉积物以黏土质粉砂和粉砂质黏土为主,从底部向上呈明显的变细趋势,并记录了1970年的强降雨事件.采用137Cs同位素测年分析,得到1963年和1986年两个时标.通过石梁河水库的沉积年代序列,推算出平均沉积速率:1963 1970年为10.85 cm/a,1970 1986年为3.81 cm/a,1986 2005年为1.32 cm/a.对比粒度沉积特征和流域降水记录,粗颗粒物质和降雨量的变化趋势基本相同,沉积物粒度组成特点直接反映了沉积时的降水、水动力搬运强度等信息.在河川来水来沙、坝前水位变化和地形等条件下,石梁河水库表现为三角洲淤积,且沉积速率逐渐变缓,符合水库淤积的一般规律.此外,石梁河水库上游建设的众多大型水库,拦截了大量泥沙,也使得沉积速率呈现减小趋势. 相似文献
8.
[专稿]长江上游水库改变干流磷通量、效应与修复对策 总被引：7，自引：6，他引：1
磷主要随河川径流循环,是水域重要营养或污染物质,是长江及河口浮游生物限制因子.在自然与人类活动作用下,磷循环规律及变化对水生态环境具有重要作用.本文根据实测资料、理论和模型系统分析了长江磷自然循环属性、水库作用及可能的环境影响.长江磷以颗粒态为主,与泥沙关系密切,受水库影响大量沉积;颗粒磷的潜在生物有效磷(BAP)较高,总量超过人类排放;自然背景下磷与淡水系统关系较小,到河口及周边海域释放BAP是这里生态系统关键的营养资源;水库拦截使在底泥沉积并在缺氧环境释放的BAP成为河流上游潜在污染源.水库拦沙也破坏了下游河流泥沙的磷缓冲机制,增加环境脆弱性,降低污染承受能力,抬高水库下泄背景溶解磷浓度和河口碳、氮的相对程度,增加干流最下游大型水库污染和水华风险.另一方面,实测资料对比研究表明,我国河流地表水环境监测规范中的磷分析方法存在问题,采用"澄清样"方法使磷大量漏测,上下游、河湖库及汛枯期间磷通量监测口径不同、标准不一,很难适应流域一体化管理要求;依此监测的评估也会严重低估水库作用,忽视其拦磷和抬高背景溶解磷等机制,误导污染源解析,影响环境管理与决策.流域水库改变泥沙、磷及循环规律是当前长江干流环境条件的实质性改变,是长江保护生态面临的主要问题和修复重点之一,建议在大型水库持续挖泥用以功能性修复河流物质通量和消除上游潜在污染内源. 相似文献
9.
对贵州省麦岗水库沉积物环境磁性特征的研究表明,亚铁磁性矿物主导了沉积物矿物磁性特征,但同时也存在反铁磁性矿物等其他矿物,超顺磁颗粒在沉积物中广泛存在.在所选矿物磁性参数中,χlf、χfd、SOFT与粒度不相关;χARM、SIRM、F300与粒度相关,但相关系数不高;χARM/χlf、χARM/SIRM和粒度显著相关,可以作为粒度的代用指标.研究结果显示,磁性参数确实可以作为粒度的代用指标.但对比研究表明,在不同沉积环境,甚至相似沉积环境的沉积物中,矿物磁性参数和粒度的关系可能不同,在特定沉积环境中,利用磁性参数作为粒度的代用指标应该在充分研究的基础上进行,使研究结果更为可靠. 相似文献
10.
通过对崩积楔沉积物进行粒度特征分析,研究崩积楔形成时的沉积条件和环境特征。沿系舟山北麓断裂,具体分析了水峪剖面、湖村剖面上各期崩积楔共21个样品的粒度及粒度参数。在崩积楔体中,砾、砂、黏土等各个粒级均有较大范围的分布,其中砾级总体概率含量达50%～70%。粒度分布为多峰态,分选差,偏度为极正偏,尖峰度>1,说明崩积楔是以砾级为主体的非均一性混杂堆积。崩积楔样品与作为物源的断层下盘样品的粒度分析对比表明,作为一种近源堆积,崩积楔的粒度特征与其下盘沉积物在粒度分布上有一定的继承性 相似文献
11.
Senapathi VENKATRAMANAN Thirunavukkarasu RAMKUMAR Irudhayanathan ANITHAMARY Govindaraj RAMESH 《国际泥沙研究》2011,(4):460-470
The distribution of grain size parameters along 11 km stretch of the beach sediments between Karikal and Nagore,reveals that the mean grain size exhibits a marked decreasing trend on either side of the mouth of the Tirumalairajanar River which flow from west to east.The sediments are mainly of medium to coarse grained,moderately sorted,near-symmetrical skewed to fine skewed and leptokurtic to mesokurtic in nature.Interrelationship of various parameters shows bimodal nature of sediments having dominance of medium to coarse sand.The major part of the sediment fall in a coarse to fine grained category(sand and silt).Based on the CM(Coarser one percentile value in micron) pattern,the sediment fall in rolling and suspension field.These factors includes the sediments discharged from the river mixes with offshore sediments and with the sediments eroded from a source rock.The effect of wave sorting, and the northward drifting of sediments by littoral current are understandable.Results indicate that the Tirumalairajanar River is the most important source for modern sediments in the study area.The agitation by waves is an important sorting mechanism in the study area,and the net sediment transport in the study area is northward.The findings are based on the grain sizes and also corroborated by shortterm observations of the beach sediment dynamics and transport during the monsoon and summer seasons between Karaikal and Nagore region. 相似文献
12.
2018年金沙江上游白格滑坡造成了近百年来最为严重的干流堵江事件,堰塞湖的形成和溃决给下游金沙江干流河道的水沙条件及梯级水电站运行造成影响.本文依据堰塞湖附近临时观测和金沙江干流河道控制性水文站的相关资料,研究堰塞体泄流对下游河道水沙输移的影响,同时结合梯级水库调度情况,计算了梯级水库的拦沙量.结果表明,堰塞湖溃决在金沙江中游形成了超历史的水沙过程,金沙江中游梯级电站开展应急调度后,堰塞湖溃决造成的特大洪水被削减为一般洪水.金沙江中游梯级梨园、阿海和金安桥电站累积拦截泥沙约1400万t,龙开口、鲁地拉和观音岩电站共计拦截泥沙约43万t,滑坡体产生的泥沙仍有约74%滞留在堰塞体附近.若滑坡体泥沙全部输移至金沙江中游梯级水库内,梨园电站的有效库容极有可能不满足水库所需调节库容的要求. 相似文献
13.
We explore the link between channel‐bed texture and river basin concavity in equilibrium catchments using a numerical landscape evolution model. Theory from homogeneous sediment transport predicts that river basin concavity directly increases with bed sediment size. If the effective grain size on a river bed governs its concavity, then natural phenomena such as grain‐size sorting and channel armouring should be linked to concavity. We examine this hypothesis by allowing the bed sediment texture to evolve in a transport‐limited regime using a two grain‐size mixture of sand and gravel. Downstream ?ning through selective particle erosion is produced in equilibrium. As the channel‐bed texture adjusts downstream so does the local slope. Our model predicts that it is not the texture of the original sediment mixture that governs basin concavity. Rather, concavity is linked to the texture of the sorted surface layer. Two different textural regimes are produced in the experiments: a transitional regime where the mobility of sand and gravel changes with channel‐bed texture, and a sand‐dominated region where the mobility of sand and gravel is constant. The concavity of these regions varies depending on the median gravel‐ or sand‐grain size, erosion rate, and precipitation rate. The results highlight the importance of adjustments in both surface texture and slope in natural rivers in response to changes in ?uvial and sediment inputs throughout a drainage network. This adjustment can only be captured numerically using multiple grain sizes or empirical downstream ?ning rules. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
14.
WANG Guixian CHEN Zhicongand ZHANG Ren Associate professor Tsinghua University. Associate Professor Tsinghua University Professor Tsinghua University. 《国际泥沙研究》1991,(1)
The fluctuationg backwater region of a reservoir has a twofold property of a river as well as a reservoir and undergoes scouring and deposition alternately. Phys- ical model simulating the fluvial processes in a fluctuating backwater region has to ensure the similarities of both scouring and deposition. This causes some difficulties in model design and the selection of model sediment. This paper describes the model study of the fluctuating backwater region of the Gezhouba Project on the Yangtze River. Plastic particles with specific gravity of 1 .056 are used. The physical. model covers a reach of mountainous river 130 km in length. The experimental results show that the total amount of deposit, its distribution along the reach, the size distribution of the deposit, and lengths of the backwater region for various discharges all agree very well with the measured data in reservoir after 5 years of operation. This fact indicates that the model design, including the selection of model sediment, is quite acceptable. 相似文献
15.
《水文科学杂志》2013,58(4):777-792
Abstract Based on data from five hydrometric stations, Pingshan station on the Jinshajiang River, Gaochang station on the Minjiang River, Wulong station on the Wujiang River, Wusheng station on the Jialingjiang River and Yichang station on the Yangtze River, a study has been made of the temporal variation in grain size of suspended sediment load in the upper Yangtze River. The results show that in the past 40 years, the grain size of the suspended sediment load in the main stem and major tributaries of the upper Yangtze River has had a decreasing trend, that can be explained by the effect of reservoir construction and implementation of soil conservation measures. The reservoirs in the upper Yangtze River Basin, all used for water storage for hydro-electric generation and/or irrigation, have trapped coarse sediment from the drainage area above the dam and, thus, the sediment released now is much finer than before the construction of the reservoirs. The downstream channels are all gravel-bedded or even in bedrock, with little fine sediment, and thus, the released flow can hardly get a supply of fine sediment through eroding the bed. Then, after the downstream adjustment, the grain size of suspended sediment is still fine. Large-scale soil conservation measures have significantly reduced sediment yield in some major sediment source areas. The relatively coarse sediment is trapped and, thus, the sediment delivered to the river becomes finer. 相似文献
16.
The physical properties of silt in river reservoirs are important to river dynamics. Unfortunately, traditional techniques yield insufficient data. Based on porous media acoustic theory, we invert the acoustic parameters for the top river-bottom sediments. An explicit form of the acoustic reflection coefficient at the water–sediment interface is derived based on Biot’s theory. The choice of parameters in the Biot model is discussed and the relation between acoustic and geological parameters is studied, including that between the reflection coefficient and porosity and the attenuation coefficient and permeability. The attenuation coefficient of the sound wave in the sediments is obtained by analyzing the shift of the signal frequency. The acoustic reflection coefficient at the water–sediment interface is extracted from the sonar signal. Thus, an inversion method of the physical parameters of the riverbottom surface sediments is proposed. The results of an experiment at the Sanmenxia reservoir suggest that the estimated grain size is close to the actual data. This demonstrates the ability of the proposed method to determine the physical parameters of sediments and estimate the grain size. 相似文献
17.
Coastal erosion that is generated by the reduction of the annual sediment yield at river outlets, due to the construction of reservoirs, constitutes one of the main environmental problems in many parts of the world. Nestos is one of the most important boundary rivers, flowing through Bulgaria and Greece, characterized by its great biodiversity. In the Greek part of the river, two reservoirs, the Thisavros Reservoir and the Platanovrysi Reservoir, have already been constructed and started operating in 1997 and 1999, respectively. The present paper constitutes the first attempt where the assessment of reservoir sedimentation effect on the coastal erosion for the case of the Nestos River delta and the adjacent shorelines is addressed in detail, through mathematical modeling, modem remote sensing techniques and field surveying. It is found that the construction and operation of the considered reservoirs have caused a dramatic decrease （about 83%） in the sediments supplied directly to the basin outlet and indirectly to the neighbouring coast and that this fact has almost inversed the erosion/accretion balance in the deltaic as well as the adjacent shorelines. Before the construction of the reservoirs, accretion predominated erosion by 25.36%, while just within five years after the construction of the reservoirs, erosion predominates accretion by 21.26%. 相似文献