The impacts of cattle access points on deposited sediment levels in headwater streams in Ireland

Cattle access to streams has been linked globally with degradation of stream water quality, driven largely by bank erosion and resultant instream, fine sediment deposition. The majority of evidence on such effects is however based in arid and semiarid regions of the United States and Australia, with few studies relating to cool temperate climates such as Northwest Europe. In this study, “Quorer” resuspendable sediment samples were taken from riffle geomorphic units upstream (control) and at two points downstream (pressure and recovery) of cattle access points in headwater streams in agricultural catchments in Ireland to assess levels of deposited stream sediment. Samples were taken in April/May (2016) prior to the grazing season and in October (2016) at the end of the grazing season. Sites in good‐high ecological status catchments and less than good ecological status catchments were included in the study. Higher levels of sediment were found downstream of cattle access points in both good‐high status and less than good status catchments; however, the impacts of access points were spatially confined to, in most cases, the area immediately downstream of the point of access. There was a strong correlation between deposited sediment mass and organic matter (OM) mass, with levels of OM increasing linearly with deposited sediment mass. Levels of measured sediment were negatively correlated with riparian habitat health (measured using a qualitative habitat assessment). The results of this study highlight the need for measures to prevent cattle access to headwater streams where access points can be many in order to manage local habitat quality and downstream water quality issues.     

杭州湾南岸滩涂沉积物中HCHs与DDTs污染特征分析

摘 要：目的 了解六六六（hexachlorocyclohexanes,HCHs）与滴滴涕(dichloro diphenyl trichloroethanes,DDTs)在杭州湾南岸滩涂沉积物中的污染现状。方法 于2018年4月，采集杭州湾南岸地区4个采样点不同深度（0~80 cm）滩涂沉积物，利用气相色谱-串联质谱法（gas chromatography tandem mass spectrometry, GC-MS/MS）测定了该区域中HCHs与DDTs的含量，对其分布规律进行分析，使用共识沉积物质量基准法对其生态学风险进行了评估。结果 所有样品中均检出，HCHs与DDTs含量分别为4.20~6.24 μg/kg与3.37~4.73 μg/kg，主要以β-HCH、δ-HCH以及DDE为主，其污染主要来源于历史性工业品，整体污染处于较低水平；20.3%的沉积物样品中DDEs含量以及28.1%的样品DDTs总量介于阈值效应浓度(threshold concentration, TECs) 和可能效应浓度(probable effect concentration, PECs)之间。结论 杭州湾南岸沉积物中HCHs与DDTs的污染处于较低水平，具有较小的生态学风险。     

流域泥沙灾害与泥沙资源性的研究

泥沙灾害与泥沙资源性是流域泥沙的重要属性,二者在一定条件下可以相互转化。本文论述了泥沙淤积、泥沙冲刷、岸滩崩塌、山地崩塌与泥石流、粗沙淤积的土地沙化等泥沙灾害,指出泥沙灾害具有时空分布的不均匀性、渐变性或突发性、群发性、转化性及危害严重性等;流域泥沙资源化的主要途径包括填海造陆及造地、引洪淤灌、堤防淤临淤背、建筑材料、湿地形成(河流、湖泊与河口海岸)等,指出流域泥沙资源化及其优化配置既要解决思想观念、基本理论、目标效益等方面的问题,还要考虑与水资源联合配置问题。     

轻质滤料滤池的试验与研究

轻质滤料滤池是以比水密度略小的滤料为滤床的滤池，通过以净水厂的原水和污水处理厂的二级处理出水为过滤试验对象，所取得的结果表明：下向流轻质滤料滤池对浊度和悬浮固体（SS）的去除率分别可以达到80％和45％，而滤床的水头损失不超过15cm。因此轻质滤料滤池可以以预过滤的形式配置在过滤处理的净水和污水的处理工艺中。     

Quantifying and characterizing contemporary riparian sedimentation

Fluvial processes of erosion, sediment transport and deposition determine the changing form and sedimentary structure of naturally adjusting riparian zones. Riparian sediment storage has both scientific and management importance in relation to: (i) the quantities of sediment that are involved; (ii) the quality of the sediment; and (iii) the dispersal of biological materials, notably the vegetation propagules that are transported and deposited in association with the sediment. After discussing the significance of riparian sedimentation processes, this paper reviews methods for quantifying contemporary sediment deposition within water bodies and their margins. Methods for investigating contemporary riparian sedimentation are given particular emphasis, and the extent to which different methods provide comparable estimates and have been used to support the analysis of different physical and chemical properties of the sediment are outlined. The importance of the following are stressed: (i) selecting a sampling method that is suited to the sedimentation environment; (ii) incorporating careful cross‐calibration if measurements from different methods are to be combined; and (iii) replicating measurements to give more robust estimates if small traps are employed. It is concluded that artificial turf mats provide a useful design of sediment trap across a range of environmental conditions because: (i) their surface roughness reduces problems of sediment removal by flood waters or rainfall; (ii) their pliability permits installation on irregular surfaces; (iii) they can be securely attached to the ground with metal pins to resist high shear stresses from river flows; (iv) they are robust and light and so easily manipulated in the field and laboratory; (v) it is possible to fully recover the deposited sediment to accurately determine the amount of sediment deposited and to support a range of other analyses. Results are presented to illustrate how artificial turf mats can be used to estimate the quantity and quality of deposited sediment and to explore the associated deposition of viable seeds. This provides one example of the important hydroecological role of riparian sedimentation processes and of the potential for the development of innovative, interdisciplinary research on riparian sediment dynamics. Copyright © 2003 John Wiley & Sons, Ltd.     

伶仃洋三维潮流输沙的数值模拟

作者使用垂向坐标变换技术，结合有限差分方法建立了三维潮流输沙的数学模型。为了增加模型的稳定性和减少数值耗散，对悬沙对流扩散方程中的水平对流项采用三阶迎风格式离散。应用本模型对伶仃洋的枯季和洪季的潮流输沙的悬沙场进行了数值模拟，将模拟结果与实测资料进行比较，二者吻合较好。模拟结果分析表明：伶仃洋悬沙运动主要集中在西滩，对伶仃航道影响不大；洪季水体含沙浓度高于枯季；水体含沙浓度沿水深存在浓度梯度，且洪季的浓度梯度明显大于枯季。     

20世纪的泥沙运动力学

在20世纪，泥沙运动力学的研究取得了不少突出的成绩，但与其他学科同时期的进展相比，发展还是比较缓慢的。按取得的进展来看，20世纪可分为两个阶段；在上半叶，有6项突破性进展，逐步积累，到1950年，Einstein集大成，提出了第1 个泥沙运动力学理论体系。在下半叶，进入了百家争鸣的时代，一些研究者提出了自己的泥沙运动理论体系，作者列举了8个有代表性的理论体系。受计算机时代的影响，从20世纪70年 代开始出现了根据大量实测资料，利用计算机进行回归分析而得出的阻力和输沙率公式，而不拘泥于发展新的理论。与此同时，一些与实际偏离较远的理论逐渐被淘汰。在21世纪，要搜集系统完整的资料，特别是近底层的资料，并拓宽研究领域到环境，生态等学科。     

黄河黑山峡河段大柳树水库比小观音水库原始库容多40亿m3的作用

一级开发大柳树高坝原始库容比二级开发小观音高坝多 4 0亿m3 ,库容大带来的好处体现在 5～ 7月可多向下游增供水量 ,缓解下游河道断流 ;延长泄放清水时间 ;增加发电效益 ;满足宁蒙河段防凌要求 ;增加汛期集中泄水 ,减缓下游河道淤积萎缩 ;满足南水北调西线工程水量调节要求等。为了更好优化配置黄河水资源 ,从全局和长远利益考虑 ,应采用一级开发方案 ,修建大柳树高坝大库     

河口水流、波浪、潮流、泥沙、河床变形二维数学模型

根据河口“波浪掀沙，潮流输沙”的泥沙运动机制，引入“波浪幅射应力”反应波浪对水体和泥沙的驱动力．考虑波浪对底部泥沙作用力、波浪对水流挟沙能力的影响及风场对水流和泥沙运动的影响．同时考虑泥沙粒径大小、水体含盐度、含沙量及水流紊动程度等因素对絮凝沉速的影响．用ＡＤＩ算法求解沿水深平均方程，破开算子法解悬移质不平衡输沙方程及河床变形方程，引入通度概念处理岸滩不规则边界，建立河口水流、波浪、潮流、泥沙、河床变形二维数学模型．通过实测资料及卫星摇感图像对所建数学模型进行检验，表明它可以较好地预测河口泥沙的运动     

泥沙输移矢量式及其应用

本文基于Parker等人泥沙输移矢量式的分析和研究，增加了上举力的作用，并考虑了泥沙颗粒受力非平衡条件，采用牛顿力学的矢量分析法，推导了泥沙输移的通用矢量式。经对公式简化，且用Ikeda和笔者试验资料的验证，证明计算值与试验值吻合较好。