Mineralogy and Distribution of Fine-Grained Sediments in Little Traverse Bay,Lake Michigan

Little Traverse Bay, northeastern Lake Michigan, contains sediments ranging in mean grain size from about 1.5? around the bay margins to 7? in the central portion. Mineralogy of the fine-grained fraction of these sediments show the four main mineral groups, quartz, feldspars, clays, and carbonates to have decidedly different distributions within the bay. Quartz and feldspar reach maxima near the center of the bay, while carbonates are highest around the edge. Clay mineral abundance reaches three separate maxima in regions characterized by very poorly sorted sediment. There are two important sources of these sediments, extensive outcrops of Devonian limestones and dolomites along the south shore of the bay and bluffs of reddish glacial till along the northwestern shoreline. Materials from these areas are transported eastward to the bay head by longshore transport incurred by the prevailing westerly winds and then return westward along the deep central trough of the bay as the wind-induced setup is relieved. Essentially all of the calcite and much of the dolomite entering Little Traverse Bay undergoes dissolution during transport resulting in the carbonate-poor sediments of the bay floor.     

长江源曲麻莱段河床沉积物分布特征

基于长江源通天河曲麻莱河段河床沉积物测量和分析,通过各参数的统计及对比,探讨沉积物粒度的基本特性及时空分布规律。结果表明:取样河段沉积物以沙砾石为主,由跃移质和悬移质成分组成,无滚动沉积,粒度参数和频率分布曲线特征显示长江源曲麻莱段河床沉积物分选较差,自然分布频率曲线多为双峰,是较典型的河流动力沉积物。而阶地沉积物则为多峰,分选差,应为河流与冰川共同作用的结果;同一断面河槽附近沉积物粒径较粗,与水流动力分布一致;洲滩沉积物粒径的垂向分布呈现粗细交替的基本规律,可反映不同历史时期河道水文节律以及青藏高原气候的定性变化。沉积物粒度的垂向分布可以为河流历史形态复原和水力反演提供基本数据。     

基于Rouse公式的紊流区悬沙粒径级配垂线分布规律

基于Rouse公式及紊流泥沙沉速公式,分别推导得到了紊流时的悬沙粒径及级配垂线分布公式,前者直接量化了泥沙“上细下粗”的垂线分布规律,后者则可用于计算不同水层及垂线上总的悬沙粒径级配。通过实例,应用粒径级配计算公式得到了不同水层的悬沙粒径级配。结果表明:泥沙粒径“上细下粗”的分布规律明显;在越远离床面的水层,细颗粒所占的比重越大,粒径分布越均匀。当考虑悬浮高度影响时,以最大粒径悬沙的最大悬浮高度为界,该高度之下级配“等宽”,该高度之上级配“上窄下宽”。     

Climatology of Large Sediment Resuspension Events in Southern Lake Michigan

Lake Michigan, particularly the southern basin, is subject to recurrent episodes of massive sediment resuspension by storm-induced waves and currents. The purpose of this paper is to investigate the climatology of these events for Lake Michigan, including an analysis of associated meteorological conditions. This paper begins by examining turbidity records from two water treatment plants (Chicago, IL and St. Joseph, MI) for which long-term records are available. The turbidity records from the two plants show significant differences indicating that turbidity measurements from a single location would probably not be representative of a basin-wide climatology. A one-dimensional sediment resuspension and deposition model for fine-grained sediments is then developed and calibrated with data from the water treatment plants. The one-dimensional model is applied at 15 points around the southern basin for a 45-year period for which Lake Michigan wave climatology is available and the results are averaged to obtain a basin-wide turbidity index (Southern Lake Michigan Turbidity Index, SLMTI). A frequency distribution of the turbidity index is presented and meteorological conditions associated with the largest events are examined. Our analysis indicates that significant resuspension events in southern Lake Michigan are usually caused by a strong cyclone passing to the east of the lake. The most likely time of the year for this to occur is October to April. There is an average of 1 event per year with SLMTI above 25 mg/L and each event typically lasts about 3 days. Our analysis indicates that events have occurred more frequently since the late 1980s as the number of winter storms has increased and ice cover has decreased.     

袁河底泥污染物监测与分析

本文通过对袁河沉积物中氨氮、总氮、总磷和COD(重铬酸钾法)含量的监测,分析袁河底泥污染物的分布规律,并通过同一断面袁河污染物与底泥中相应污染物含量的对比,研究底泥污染物的来源,由此得出除个别断面外,沉积物中污染物含量高的断面河水中的含量相应的也较高。对比袁河与太子河流域可知,袁河流域沉积物污染程度远低于太子河流域。这就为维持袁河河流生态健康,合理利用袁河水资源提供了依据。     

Flocculation of Fine-Grained Lake Sediments Due to a Uniform Shear Stress

Experiments were performed to investigate the effects of fluid shear on the flocculation of fine-grained lake sediments in fresh water. In these experiments, a Couette viscometer was used to apply a uniform shear stress to a sediment suspension. The sediments were from the Detroit River inlet of Lake Erie. They were prepared such that the initial (unflocculated) size distribution contained approximately 90% of its mass in particles less than 10 μm in diameter with the average diameter being about 3.5 μm. Experiments were performed at shear stresses of 1, 2, and 4 dynes/cm² and sediment concentrations of 50, 100, 400, and 800 mg/L, values which are characteristic of those found in the Great Lakes. Data in the form of floc size distribution as a function of time were obtained. For steady-state conditions, the median diameters of the flocs formed were typically 20 to 100 μm depending on shear stress and sediment concentration. Quantitative results for the decrease in the steady-state floc size with increasing shear stress and with increasing sediment concentration were obtained. The times required for flocculation to occur under different conditions were also determined and were typically on the order of 1 hour.     

泥沙粒径与水流紊动关系试验研究

挟沙水流中的泥沙颗粒因水流紊动而悬浮，同时受重力作用而下沉。由于水流中的泥沙颗粒会对水流紊动产生影响，反之，水流紊动也对泥沙颗粒分布产生影响，它们之间作用是相辅相成的。本文采用超声流速仪（MicroADV）量测挟沙水流的时均流速沿垂向分布，同时对泥沙颗粒粒径的分布进行了试验，研究了泥沙颗粒粒径d50和水流紊动强度在沿垂向分布之间的内在联系，结果表明：泥沙颗粒粒径和紊动强度沿垂线的分布一致性较好，并用实测资料对他们进行了拟合，建立了它们之间的关系式，有一定的实用价值。     

长江河口涨潮槽泥沙运动规律

30年来，在对涨潮槽性质和水沙条件有所了解的基础上，于2001年洪季和2003年枯季又一次对长江口新桥水道和南小泓两条典型涨潮槽及与其相邻的南支和南港主槽(落潮槽)的水流、泥沙和河床沉积物进行观测，并进行了专题研究。结果表明：潮流历时涨潮比落潮短；潮流和单宽潮量涨潮比落潮大，优势流小于50％，净水流向槽顶方向：涨潮含沙量、单宽输沙量大于落潮，优势沙小于50％，净输沙向槽顶方向；悬沙粒径组成较细，河床泥沙粒径组成较粗，河床存在推移质泥沙运动，并形成微地貌沙波。     

新型平流式沉淀池沉淀效果试验研究

在进水口加设调流板、在溢流堰上沿水流方向设置溢流槽,从两个方面对传统平流式沉淀池进行了改进,设计出一种新型平流式沉淀池。通过试验研究分析了调流板和溢流槽对泥沙沉淀效果的影响,得出新型平流式沉淀池可以大大提高泥沙的沉淀效率,出池水流平均含沙量最大降幅可达94.8%,特别是对细颗粒泥沙的沉淀效果尤为明显。     

Adsorption of phosphorus in sediment re-suspension under sudden expansion flow conditions

Based on the study of hydraulic characteristics of the sudden expansion water flow of an annular flume, this paper determines the vertical velocity distribution and the turbulence intensity distribution in the mainstream and the recirculation regions to analyze the basic features of this flow field. The adsorption of the phosphorus in the sediment is studied by adding the bacteriostatic agent. The results show that the flow speed in the mainstream region is higher than that in the recirculation region. However, the turbulence intensity in the recirculation region increases more than that in the mainstream region. The adsorption of the phosphorus in the sediment includes the physisorption and the biosorption, and the former is stronger than the latter. With the biosorption in the phosphorus removal process, the phosphorus released by the sediment is mainly completed by the poly-P bacteria in the anaerobic condition. The adsorption of the phosphorus in the sediment in the mainstream region of a sudden expansion water flow is strong and stable, whereas the adsorption in the sediment in the recirculation region is largely fluctuated.     

海河流域典型河流沉积物粒度特征及分布规律

为了解海河流域典型河流沉积物粒度参数空间分布规律,对海河典型河流的表层沉积物进行采集并利用Mstersize2000激光粒度仪进行粒度分析。结果表明,海河典型河流沉积物平均粒径差异显著,分选状况总体较差;山区水系与平原水系相比,沉积物平均粒径减小,呈集中分布,水动力减弱;山区自北向南变化明显,水系沉积物平均粒径减小,分布集中化,分选状况变差,由极正偏-正偏,向对称方向变化,峰度向平坦方向趋近,水动力减弱,符合粒径自然变化规律;平原区水系沉积物粒径参数表明南北变化不明显,因受较多支流、河流-湖泊-洼淀湿地等复杂系统和人为干扰强烈的影响,南北无显著变化规律。总的来说,海河流域河流受人为干扰强度较大,河流沉积物源较为复杂,栖息地物理完整性差。     

汤浦水库泥沙冲淤分布数值模拟

泥沙淤积不仅影响水库库容,其中大量污染物还会影响水库水质。运用MIKE21软件对汤浦水库泥沙分布进行模拟研究。结果表明:泥沙在库区分布不均,河流入库位置淤积较少,局部甚至有冲刷;库区中部是泥沙淤积主要地带,模拟最大淤积厚度约30 cm;坝前位置淤积最小,厚度约为12 cm。模拟结果与沉积物淤积厚度采样结果一致,说明该模型能合理模拟汤浦水库沉积物分布状况。模型提供的沉积物分布状况对控制汤浦水库内源污染有一定参考价值。     

查干湖连通水系的沉积物响应及特征

本文探讨了查干湖自然和人为连通水体的沉积物组成和分布特征。研究发现查干湖沉积物组成特征与自然连通水体霍林河和嫩江有较好的一致性。自然和人为过程的水源补给使得一些矿物发生了迁移,其中石英的累积效应最为明显,湖泊中的碳酸盐主要来自于河流的输入。径流特征和人为活动显著影响着查干湖沉积物的组成分布。从湖区到引水和退水区域,细颗粒含量明显减少而粗颗粒含量明显增加,一些矿物、有机质颗粒物会从引水区域输入至湖区和退水区域逐渐累积。     

Small-scale lacustrine drifts in Lake Champlain,Vermont

High resolution CHIRP (Compressed High Intensity Radar Pulse) seismic profiles reveal the presence of two lacustrine sediment drifts located in Lake Champlain's Juniper Deep. Both drifts are positive features composed of highly laminated sediments. Drift B sits on a basement high while Drift A is built on a trough-filling acoustically-transparent sediment unit inferred to be a mass-transport event. These drifts are oriented approximately north–south and are parallel to a steep ridge along the eastern shore of the basin. Drift A, located at the bottom of a structural trough, is classified as a confined, elongate drift that transitions northward to become a system of upslope asymmetric mudwaves. Drift B is perched atop a structural high to the west of Drift A and is classified as a detached elongate drift. Bottom current depositional control was investigated using Acoustic Doppler Current Profilers (ADCPs) located across Drift A. Sediment cores were taken at the crest and at the edges of the Drift A and were dated. Drift source, deposition, and evolution show that these drifts are formed by a water column shear with the highest deposition occurring along its crest and western flank and began developing circa 8700–8800 year BP.     

Depth distribution and mobility of a harpacticoid copepod within the bed sediment of an alpine brook

The harpacticoid copepod Limnocamptus echinatus (Mrazek) shows a very distinct large-scale vertical distribution within the bed sediments of Oberer Seebach, a second-order gravel stream. The population peak appears in a sediment layer between 15 and 35 cm over long periods on average. Abundances are significantly lower in the topmost sediments and sediment layers below 50 cm depth. The large-scale vertical distribution is mainly influenced by the changes and pattern of temperature and discharge, which influences the current velocity of the surface and interstitial water. Effects appear quite different, when permanent flooded areas and areas that periodically fall dry on the surface are compared. Limnocamptus echinatus is forced deeper into the sediments of the gravel bar during low water temperatures and/or high discharge situations. On permanent flooded areas the vertical distribution is more stable over long periods, but higher fluctuations occur during short periods. The Limnocamptus echinatus population shows higher mobility in deeper sediment layers (40 to 60 cm sediment depth). Comparing longer periods, water flow and the transport of fine material differ in deeper sediment layers. The water current is much slower, producing a tendency for fine material sedimentation. This might be the main reason for the higher mobility in deeper sediment layers and the restriction of 90 per cent of the Limnocamptus echinatus population to a sediment depth of 50 cm. High mobility in vertical and horizontal directions within the bed sediments is interpreted as normal reactions and adaptations to the dynamic behaviour of the system, mainly forced by physical parameters. Biological parameters appear as subdominant for large-scale vertical distributions.     

Identification and Determination of Trace Organic Substances in Sediment Cores from the Western Basin of Lake Ontario

A study was carried out to identify and to determine organic chemicals in sediment from the western basin of Lake Ontario, particularly in the fine-grained sediments near the mouth of the Niagara River. Sediment cores were obtained at five sampling stations, and samples were extracted by the base/neutral and acid method designed by US Environmental Protection Agency for extraction of water samples. The identification of organic compounds in the base/neutral sediment extract was carried out by GC/MS techniques. The major classes of investigated contaminants were aromatics, polynuclear aromatics, alkylated polynuclear aromatics, alkylated benzenes, phthalates, methyl esters of fatty acids, olefins, aldehydes, chlorobenzenes, and benzoates. In addition, all sediment samples were analysed for 2,3,7,8-tetrachloro dibenzo-p-dioxin. In the surface sediments, the abundance of contaminants decreased with the distance from the Niagara River mouth toward the north-west. However, high concentrations of most of the detected organics were present in sediment at the station located east of the River mouth.     

黄河水滴灌系统灌水器结构-泥沙淤积-堵塞行为的相关关系研究

传统的黄河水沉淀-过滤系统存在沉沙池建设成本高、过滤器频繁反冲洗能耗高等问题,让更多的细颗粒泥沙随水流排出灌水器体外是解决黄河水滴灌系统灌水器堵塞的新思路,而摸清泥沙在黄河水滴灌系统内部的淤积特性以及灌水器结构-淤积泥沙特性-堵塞特性参数间的相关关系是探索其排沙能力的前提和基础。为此,本文在河套灌区开展了黄河水滴灌系统灌水器堵塞原位试验,系统分析了6种内镶贴片式灌水器内部细颗粒泥沙含量及粒径分布动态变化特征,探索了三者间的级联关系。结果表明：进入灌水器内部的泥沙99%以上可以排出体外,淤积在灌水器内部的泥沙以粉粒为主、砂粒次之、黏粒最少。随着灌水器堵塞加剧,内部淤积泥沙的黏粒、粉粒比例相对降低,而砂粒比例相对增加,泥沙进入灌水器后存在聚集等行为,使得灌水器内部淤积泥沙粒径明显高于毛管入口。泥沙比表面积淤积量、粉粒比例、砂粒比例、D₅₀、D₉₅对黄河水滴灌系统Dra、克里斯琴森均匀系数CU影响显著（p<0.05）,不同灌水器淤积泥沙粒径明显不同,D₅₀与灌水器结构无量纲参数（流道宽深比W/D、面积长度比A^1/2/L）及断面平均流速v显著（p<0.05）相关。本研究对引黄滴灌灌水器设计及灌溉系统过滤配置具有指导意义。     

Submerged macrophyte communities and the controlling factors in large,shallow Lake Taihu (China): Sediment distribution and water depth

Lake Taihu, the third largest lake in China, is subjected to severe eutrophication and cyanobacterial blooms as a result of development and urbanization. In order to restore the degraded lake ecosystem, it is important to identify which environmental factors control the submerged macrophytes which declined during eutrophication. To characterize community structure of submerged macrophytes and to assess the plant–environmental relationships in Lake Taihu, a monthly investigation was conducted from May to October in 2010. A total of six species were recorded, dominated by Potamogeton malaianus and Vallisneria natans. Multivariate analysis showed that water depth, depth of soft sediments and nutrient variables (orthophosphate of water, organic matter of sediment, total nitrogen and total phosphorus of sediment) were the major factors determining growth and community composition of submerged macrophytes in the lake. A strong predictive association of soft-sediment depth and plant biomass indicated preference of submerged macrophytes for firm bottoms along the eastern shore and approximately 0.2 m could be regarded as an optimum depth for the growth of plants. The biomass of plants responded proportionately to water depth, and approximately 1.8 m could be regarded as the optimum depth for the growth of submerged macrophyte in Lake Taihu. Our results indicated that improvement of habitat and the selection of appropriate submerged macrophytes species are very important for ecological restoration in large eutrophic lakes. This study could provide useful information for managers and policy makers to evaluate and modify restoration practices in large, shallow lakes.     

三湖河口～头道拐段槽蓄水增量影响因素分析

通过2006～2012年6个凌汛年度的实际的气温、槽蓄水增量等因素统计分析,表明近几年黄河内蒙古河段大部分槽蓄水增量主要集中在三湖河口～头道拐段,凌汛期上游来水径流量增大是槽蓄水量增大的主要原因。槽蓄水增量增大与河道淤积及不断修建河道内建筑物导致河道过流能力减小也有一定关系;气温的剧烈变化是槽蓄水增量增大一个重要因素。槽蓄水增量增大主要受上游来水、气温变化、河道边界条件及河道内建筑物等综合因素影响。     

The use of flux-corer experiments in the determination of heavy metal re-distribution in and of potential leaching from the sediments

Metal dynamics between sediments, interstitial water and overlying water are particularly complex. The movement of metals, their availability, and possible toxicity are influenced by various chemical and physical reactions and factors such as oxygen/redox gradients, pH, grain size, etc. To study the impact of oxygen on the release from and the re-distribution of Cd, Pb, Zn and Cu in sediments, flux-corer experiments have been optimised and performed.The flux experiment was carried out using 3 identical sediment cores. The first (control) sediment core was completely characterised before, the two other cores after the experiment. Pore water extractions and sequential extractions were performed on 2 cm depth intervals throughout the 20 cm long sediment cores.In the flux experiment, the sediment cores were exposed to a small volume of overlying water, which was continuously renewed. The change of trace metal mobility was assessed by following concentration-changes in the outflow. It has been found by the use of the flux-corer experiment, that the Cd, Pb, Zn and Cu concentrations in the outflow are at least 3–6 times higher during oxic conditions. Flux-corer experiments can be useful tools to facilitate the study of the change of heavy metal mobility and distribution in the sediment induced by the change in surface water policy.