胶体颗粒在潜流带中沉积过程及机制

潜流带是河流地表水和地下水交混区域,是河流中重要的物质能量交换和水生生物栖息的场所,而胶体颗粒在潜流带中沉积,会改变潜流带中的水动力结构和生态环境。本文利用室内循环水槽实验和多物理场耦合的数值模拟方法,旨在研究胶体颗粒在河流上覆水与潜流带中的迁移过程和胶体颗粒在潜流带中沉积分布特征及其对不同因素的响应规律。结果表明:河流上覆水中胶体会逐渐被河床截留且截留胶体集中于河床浅层;沙波水平方向截留量呈现出迎水面较高、背水面较低的趋势;胶体在潜流带沉积的主要机制是潜流交换、颗粒沉降与河床截留作用。本文能为胶体颗粒在潜流带中的生态环境作用研究提供科学依据,并为河流生态环境修复、河流健康管理提供理论支持。     

潜流带水文-生物地球化学:原理、方法及其生态意义

精确量化潜流带水文交换和生物地球化学反应一直是一个挑战,潜流带水文-生物地球化学研究的核心任务是将小尺度上的水文通量及生物地球化学反应动力学与更大尺度上它们对河流水质和生态的累积效应关联起来.基于潜流带水文-生物地球化学耦合原理,系统综述了渗流仪测量、测压管测量、示踪剂注射试验、温度示踪等潜流带水文学研究方法以及野外示踪试验、室内培养试验等生物地球化学研究方法,针对性地评述了潜流带水文-生物地球化学过程在更大尺度上的累积效应及其对河流生态系统的重要意义,并指出未来的研究将从潜流带研究技术方法的先进化、水文地貌理论与模型的深入化和潜流带生物地球化学过程的尺度化等方面持续地发展.      

河道潜流交换水动力过程现场监测研究进展

河道潜流带是河水与地下水交互作用的关键过渡区,具有高度的动态性和敏感性,频繁的水力交换易引发其内部的生物地球化学反应,并对河流生态安全产生重要影响。为提高河道潜流交换水动力监测结果的真实性和有效性,介绍渗流、水压、溶质、温度等监测方法及其适用性,归纳河床和河岸的监测点布设参数和不同监测手段的数据采集频率,系统总结河段、河床及河岸的潜流交换理论与计算方法,探讨导致潜流监测结果不确定的因素。针对现有监测方法的不足和未来研究的发展方向,提出今后需加强多方法联合监测和多技术集成的应用,开展河岸侧向潜流监测及不确定性分析等工作,为潜流带水文-生物地球化学过程耦合机制研究提供可靠数据。     

平原河流水沙界面生源物质迁移转化过程及水环境调控的研究进展

生源物质作为影响水质的重要因素,其在河流中的迁移转换一直倍受关注。水沙界面物质交换过程受众多环境和水动力因素的影响,过程极其复杂,不仅影响着河流生源要素的通量演变规律,还关系到河流水环境问题。为探究水沙界面生源物质迁移转化过程及作用机制,结合国内外研究最新进展,对泥沙颗粒与生源物质的微界面作用、水沙界面对生源物质的迁移转化作用、水流条件对泥沙吸附解吸生源物质作用机理进行总结和概述,总结阐述了河流水质模型和闸坝泵条件下的水环境调控模型,最后指出平原河流水沙运动对生源物质输运作用机理及水环境调控。针对上述已有的研究成果和存在不足,对今后研究方向提出展望。     

河床沉积物非均质性影响下的潜流交换数值模拟

为了揭示河床沉积物非均质性对潜流交换的影响,构建了沙波地形作用下的地表水-地下水耦合模型,通过生成不同的渗透系数随机场,讨论了不同地表水动力过程和河床沉积物非均质性对潜流交换通量、交换空间及平均停留时间的影响规律。结果表明,所构建的地表水-地下水耦合模型能够准确刻画水沙界面附近流场,模型具有良好的适用性;均质或非均质河床沉积物情景下,水沙界面上的平均交换通量、停留时间与雷诺数之间均呈现幂函数关系,潜流交换深度则在地表水进入完全紊流之后趋于稳定。结果还表明,较强的河床沉积物非均质性能够有效增强水沙界面上潜流交换通量和空间交换频率,但会制约潜流交换空间并缩短水流在潜流带中的停留时间。     

河床起伏条件下生物堵塞对潜流带氮素迁移转化的影响

生物作用造成河床於堵普遍存在,并受到多种环境因素的影响.以往研究较少考虑生物堵塞对潜流带氮循环的影响.采用数值模拟方法建立水流-溶质运移-生物生长耦合模型,模拟河床驱动下的潜流交换过程,探讨生物堵塞作用对氮素迁移转化的影响.研究表明:生物作用导致沙丘表面形成堵塞层和生物聚集区,并限制了NO_3~-的运移深度,潜流带中以NH_4~-为主;河水中充足的有机碳会增大堵塞程度,促进反硝化作用去除NO_3~-;强烈的河床起伏和较大的河流流速均会增大沙丘表面的压力差,增大堵塞范围和细菌生物量,从而加快硝化和反硝化作用速率,有利于NO_3~-、NH_4~-的去除.生物堵塞作用有利于氮污染物的去除,且主要受到河床表面的压力梯度和异养细菌生物量的影响.     

基于连通性恢复的潜流带生态修复研究进展

潜流带是流域生态修复的关键区域之一, 潜流带修复的根本目标是恢复水系间的能量流通、物质传递和信息流动, 即恢复潜流带的连通性。对于潜流带连通性恢复而言, 应统筹考虑水文连通性、生态连通性和功能连通性等多层次的内容。潜流带生态修复相关研究主要基于流体动力学、地质学和生态学等基础理论, 剖析潜流驱动的生物地球化学耦合机制, 研发可促进潜流交换和恢复生物多样性的生态修复技术, 实现潜流带水文条件的改善与生物物种的恢复, 进而达到潜流带生态系统结构和功能综合性修复的目的。本文从潜流带水文连通性、生态连通性和功能连通性等多层次出发, 从潜流带流体动力学性能、介质性能、生物群落组成、食物网结构及环境生态功能等方面, 综述基于生态修复目标的潜流带连通性恢复理论与技术进展, 以实现潜流带生态系统整体稳定性的提升。在未来潜流带生态修复理论与应用研究中, 需发挥多学科交叉的优势, 耦合多组学方法对潜流带生态过程进行微观探索, 系统探究时间和空间尺度上潜流带生态修复过程的演替规律, 进一步构建多因素作用下的潜流带生态修复框架体系。     

分布式水文模型中河流水深及其与地下水相互作用的耦合模拟

大尺度流域水文模型一般只模拟河道径流,对河流水深和流速并不关注。在进行河流-地下水相互作用模拟时,河流水深（水位）是一个重要因素,其时空变化及其对河流-地下水水量交换的影响应加以考虑。本文就流域分布式水文模型中河流水深的时空变化计算及其与地下水的实时耦合模拟进行了研究,提出了相应的计算方法,改进了大尺度水文模型WATLAC,并通过V-型流域考题进行了检验。模拟结果显示,模型有效地模拟了V-型流域的河流水深、地下水水位沿河道的时空变化以及河流与地下水的水交换量,揭示了河流-地下水相互作用关系在降雨过程中的变化规律及主控因子。此外就河床糙率对河流水深及河流与地下水间水交换量的影响做了模拟分析,发现河床糙率的改变将影响河流水深,从而进一步影响河流与地下水的水交换量。本文提出的算法较为真实地模拟了河流洪水演进过程及其对河流-地下水相互作用的影响,模型适用于河流-地下水相互作用明显的区域,可作为评估地表-地下水相互影响的有效计算工具。     

潜流交换温度示踪方法研究进展

潜流带是河流生态系统中活跃的生态群落交错区,是地表水和地下水相互作用的重要界面。研究潜流带内存在的潜流交换机制对评估水资源的开发利用以及维持和修复河流生态系统健康有着重要意义。系统介绍了温度示踪方法的一维垂向稳态和瞬态热运移解析模型,梳理归纳了基于温度示踪的时序数据采集方法、信号分析方法和数值方法的相关研究进展,最后对比论述了温度示踪方法的优势和存在的主要问题,同时指出了地下水的多维流动、温度测量的不确定性以及非理想条件对解析模型的影响仍是未来温度示踪方法需要进一步研究的重点。     

弯曲河岸侧向潜流交换试验

为揭示河岸形态引起的侧向潜流交换规律,利用地表水与地下水双循环水槽系统,通过10组正弦型微弯河岸与4组直线型河岸的潜流交换对比试验,研究不同河岸振幅a、地表水流速u、河流水深h条件下的潜流交换特性。试验结果表明,与垂向潜流交换机理类似,侧向潜流交换也存在对流(泵吸交换)、扩散和微循环3种交换形式。河流雷诺数Re的增大,将加强紊动扩散与微循环作用。河岸弯曲形态的出现,将引起泵吸效应,大大加剧了河岸的潜流交换,且随着河岸振幅与河流流速的增大,河岸形态引起的泵吸交换将逐渐成为潜流交换前期的主要形式。     

A review on using heat as a tool for studying groundwater–surface water interactions

In terms of the research on groundwater–surface water heat-tracing methods, investigation of the interactions within the compound system of the groundwater–surface water–hyporheic zone can effectively reveal the relevant physicochemical processes and microbial properties. The evaluation of these properties represents a key component in qualitative and quantitative research on groundwater–surface water interactions. Therefore, this paper reviews the research results on groundwater–surface water interactions achieved by related researchers using heat as a natural tracer over the last decade. In connection with the application of heat-tracing theory to the basic principles of hyporheic exchange between groundwater and surface water, research on groundwater–surface water interaction through one-dimensional steady-state and transient-state heat transport analytical models, techniques to collect and analyze temperature time series data, and numerical simulation technology is reviewed. In addition, directions for future research using groundwater–surface water heat-tracing methods are suggested. First, hypothetical, difficult temperature boundary and hydrogeological conditions require further research. Second, hydrodynamic exchange capacity and the processes of heat exchange and solute concentration exchange in the hyporheic zone alongside riverbeds should be appropriately and accurately measured under multi-scale influences. Third, the overall study of the heat transport process inside the hyporheic zone induced by complex riverbed forms should be performed, and the response mechanism of riverbed hyporheic exchanges driven by riverbed form, the hydrodynamic force of surface water, and sediment permeability should be revealed. The objectives and goals of this paper are to encourage scholars interested in analyzing groundwater–surface water interactions using heat as a tracer to creatively solve practical problems and to improve the ecological functions of river aquatic habitats through new research results.     

Research Advance of Changing Biogenic Substance Cycling in River Systems by Damming*

River damming transforms allotropic natural rivers into autotrophic 'impound river' (referred to "reservoir"), which changes the processes of river biogenic substance cycle and the matter properties as well as export flux from land to ocean, thus becoming one of the key problems of element biogeochemical cycle. Due to the different behavior of biogenic substances (C, N, P, Si) in biological processes, biogenic substances cycle efficiency is different, in turns, Silicon (Si)>Organic Carbon (OC)>Phosphorus (P). The migration and transformation processes of C and Si are significantly affected by phytoplankton and water retention time. Nitrogen (N) and P are mainly affected by water pH, temperature, Dissolved Oxygen (DO) and retention time. The retention efficiency of biogenic substances is shown as N>C>P>Si at the global scale. Besides, the sedimentation and burial processes of reservoirs constitute the net sink of OC in rivers. River damming alters the stoichiometric characteristics of water elements, nutrient constraints, aquatic communities composition and the coupling effect of C/N/P/Si. The stable isotopic compositions of C, N and Si can effectively trace the source, migration and transformation of biogenic matter. A combination of elements stoichiometric characteristics and stable isotopic composition could effectively indicate the change of source materials in reservoirs. With the increasing demand for clean energy, the intensity of river damming and reservoir construction will increase. Thus, a series of scientific problems including changing law of biogenic substance migration and transformation dynamic, as well as accumulation effect of ecological environment in watershed systems by river cascade damming, should need to be concerned in the biogeochemistry cycle study.     

大坝下游河岸带冬夏季水热交换特征对比

为对比水库下游河岸带冬夏季潜流交换特征及温度场分布规律,在新安江大坝下游开展了河道水、河岸带地下水的水位与温度监测,并结合达西定律推广式等理论进行了分析。结果表明:不论冬夏季,侧向潜流交换量与河道水位呈逆时针“绳套”关系,且离河道越近潜流交换强度越大;冬、夏季潜流交换强度与补给方式存在明显不同,在近河岸处单宽交换总体积分别为55.23 m3（周）、75.08 m3（周）,夏季主要为河道补给河岸带,冬季相反,此外,夏季交换范围更大且交换更快;河岸带温度场受低温波动水影响显著,在垂直方向上夏季表现为“上暖下凉”,冬季相反,在水平方向上夏季低温传播距离较大,且具有明显的分区。因此,在水库下游河流生态治理过程中,应适当考虑不同季节的影响。     

水位变化影响下的河水-地下水侧向交互带地球化学动态

为了解不同水位变化影响下的河水与地下水侧向交互带地球化学特征动态,以重庆市马鞍溪为研究对象,选取丰水期向枯水期过渡的10-12月为研究期,对河水、地下水及交互带的水位、水温、溶解氧（DO）、pH值、电导率（EC）进行监测,结合对水体主要离子浓度的分析。结果表明,随枯水期到来,侧向交互带水位发生较大变化,交互带与河水间的水位梯度缩小,河水入渗动力逐渐减弱。水位的变化及入渗水温的降低,使交互带微生物活动减弱,pH值上升且变幅减小,DO上升。在其影响下,交互带EC下降,变幅减小,交互带对NO₃-、SO₄2-的净化能力降低,对Mn、Zn等重金属固定能力增强。通过分析交互带地球化学特征的变化,可推断出随马鞍溪枯水期的到来,侧向交互带边界由距河岸30~50 cm移动至距河岸30 cm以内。     

Groundwater flow,nutrient, and stable isotope dynamics in the parafluvial-hyporheic zone of the regulated Lower Colorado River (Texas,USA) over the course of a small flood

Periodic releases from an upstream dam cause rapid stage fluctuations in the Lower Colorado River near Austin, Texas, USA. These daily pulses modulate fluid exchange and residence times in the hyporheic zone where biogeochemical reactions are typically pronounced. The effects of a small flood pulse under low-flow conditions on surface-water/groundwater exchange and biogeochemical processes were studied by monitoring and sampling from two dense transects of wells perpendicular to the river. The first transect recorded water levels and the second transect was used for water sample collection at three depths. Samples were collected from 12 wells every 2 h over a 24-h period which had a 16-cm flood pulse. Analyses included nutrients, carbon, major ions, and stable isotopes of water. The relatively small flood pulse did not cause significant mixing in the parafluvial zone. Under these conditions, the river and groundwater were decoupled, showed potentially minimal mixing at the interface, and did not exhibit any discernible denitrification of river-borne nitrate. The chemical patterns observed in the parafluvial zone can be explained by evaporation of groundwater with little mixing with river water. Thus, large pulses may be necessary in order for substantial hyporheic mixing and exchange to occur. The large regulated river under a low-flow and small flood pulse regime functioned mainly as a gaining river with little hydrologic connectivity beyond a narrow hyporheic zone.     

非稳态潜流交换过程研究进展

潜流交换研究涉及地表水-地下水系统交互作用的物理机制、影响因素和生化作用等方面,是近年来水文学、生态学、环境学等学科的研究热点。潜流交换过程包含水流运动、溶质运移以及能量传输过程。以稳态流动条件作为控制因素的潜流交换研究成果已经不能满足相关学科发展的要求。因此,近年来非稳态潜流交换过程的研究及其成果渐受关注。当前相关研...     

A large-scale study of hyporheic nitrate dynamics in a semi-arid catchment,the Tafna River,in Northwest Algeria

Very few studies have evaluated the role of the hyporheic zone (HZ) in aquatic ecosystem functioning or the factors driving hyporheic exchange flows on a large scale, especially in a semi-arid environment such as the Tafna watershed in Algeria. To understand this role through time and space, hydrogeochemical parameters, particularly nitrate concentrations (NO₃–N), were measured monthly between February 2013 and April 2014 in surface water (SW), interstitial water (IW) and groundwater (GW) along a 170-km stretch from the river’s source to the outlet into the main stream of the Tafna River and its Isser and Chouly tributaries. The significant longitudinal evolution of NO₃–N in the HZ was related to stream order and distance from the source. Moreover, the study indicated a significant difference between nitrate concentrations in the riffles (R) and pools (P) of the Tafna wadi. Principal component analysis (PCA) revealed the considerable impact of agriculture on nitrate concentrations. This study indicated on a large scale that nitrate-rich HZ contributed to increasing surface nitrate concentrations in upwelling sites and could be an important nitrate source for downstream SW, particularly during low-water (LW) periods when the Tafna can run dry on the surface. Thus, these results underline the importance of hyporheic zones functioning to the water quality of the watershed (process of enrichment and retention of nitrogen).     

汉江下游河水-地下水侧向交互带中溶解态锰的分布特征

江汉平原浅层地下水中锰含量普遍较高,探究锰在河流交互带中的分布特征有助于认识交互带中锰的生物地球化学过程,对水质的保护具有重要指导意义.通过监测汉江下游侧向交互带河水、地下水中溶解态锰含量及其相关指标,分析不同河水-地下水交互作用方向下溶解态锰的时空分布规律,并探讨其成因.结果表明:研究区侧向交互带中靠近河岸带区域存在溶解态锰的富集,且在有局部反向流的地方锰含量较高;该局部富集的现象在河水补给地下水的交互带中更加明显;泄洪后该富集区域随水流方向发生迁移;研究区地下水中锰的含量与HCO₃-、Ca2+、Mg2+呈极显著正相关,与NO₃-、Fe2+显著负相关,但与交互带地下水中Eh和pH不相关.交互带溶解态锰的时空分布受地形条件、水动力和水化学的共同影响.