Modelling of the retreat process of composite riverbank in the Jingjiang Reach using the improved BSTEM          下载免费PDF全文

Quanli Zong  Junqiang Xia  Meirong Zhou  Shanshan Deng  Yi Zhang 《水文研究》2017,31(26):4669-4681

Bank retreat in the Jingjiang Reach is closely related not only to the near‐bank intensity of fluvial erosion but also to the composition and mechanical properties of bank soils. Therefore, it is necessary to correctly simulate bank retreat to determine the characteristics of fluvial processes in the Jingjiang Reach. The current version of bank stability and toe erosion model (5.4) was improved to predict riverbank retreat, by inputting a dynamic water table, and calculating the approximation of the distribution of dynamic pore water pressure in the soil near the river bank face, and considering the depositional form of the failed blocks, which is assumedly based on a triangular distribution, with the slope approximately equalling the stable submerged bank slope and half of collapsed volume deposited in the bank‐toe region. The degrees of riverbank stability at Jing34 were calculated using the improved bank stability and toe erosion model. The results indicate the following trends: (a) the degrees of riverbank stability were high during the dry season and the rising stage, which led to minimal bank failure, and (b) the stability degrees were low during the flood season and the recession stage, with the events of bank collapse occurring frequently, which belonged to a stage of intensive bank erosion. Considering the effects of bank‐toe erosion, water table lag, and the depositional form of the collapsed bank soil, the bank‐retreat process was simulated at the right riverbank of Jing34. The model‐predicted results exhibit close agreement with the measured data, including the total bank‐retreat width and the collapsed bank profile. A sensitivity analysis was conducted to determine the quantitative effects of toe erosion and water table lag on the degree of bank stability. The calculated results for toe erosion indicate that the amount of toe erosion was largest during the flood season, which was a primary reason for bank failure. The influence of water table lag on the degree of stability demonstrates that water table lag was an important cause of bank failure during the recession stage.  相似文献   

Shallow groundwater dynamics and its driving forces in extremely arid areas: a case study of the lower Heihe River in northwestern China          下载免费PDF全文

Ping Wang  Jingjie Yu  Sergey P. Pozdniakov  Sergey O. Grinevsky  Changming Liu 《水文研究》2014,28(3):1539-1553

Shallow groundwater is an important source of water for the maintenance and restoration of ecosystems in arid environments, which necessitates a deeper understanding of its complex spatial and temporal dynamics driven by hydrological processes. This study explores the dominant hydrological processes that control the shallow groundwater dynamics in the Gobi Desert‐riparian‐oasis system of the lower Heihe River, a typical arid inland river basin located in northwestern China. The groundwater level and temperature were monitored in 14 shallow wells at 30‐min intervals during the 2010–2012 period. After combining this information with meteorological and hydrological data, a comprehensive analysis was conducted to understand the dynamic behaviour of the shallow groundwater system and to determine the dominant factors that control the groundwater flow processes. The results of the study indicate notably large temporal and spatial variations in both the groundwater level and temperature. Noticeable fluctuations in the groundwater level (0.5–1 m) and temperature (4–8 °C) were observed in the riparian zone, evidencing a clear river influence. In comparison, the groundwater fluctuations in the Gobi Desert were more stable (the annual variations of the water table were less than 0.5 m, and the water temperature varied by no more than 2 °C). Strong variations in the groundwater table (1.5–5.0 m/year) and temperature (1.5–6.5 °C), mainly caused by surface flood irrigation and groundwater pumping, were observed in the oasis area. The investigated sites were categorized into three types that reflect the dominant hydrological processes: (1) the riparian zone, dominated by riverbank filtration and groundwater evapotranspiration; (2) the Gobi Desert area, controlled by groundwater evaporation and lateral recharge; and (3) the oasis area, dominated by groundwater evapotranspiration as well as surface–groundwater interactions caused by human activities. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

ICP-MS测定甘肃某农场大气颗粒物中的铬、铜、砷、镉、铅含量     

胡小耕  高永宏 《甘肃地质》2011,(3):89-92

空气滤膜吸附采集甘肃某农场大气粉尘样品,采用盐酸—硝酸—氢氟酸—高氯酸溶解,电感耦合等离子体质谱法（ICP-MS）同时测定溶液中铬、铜、砷、镉、铅等重金属元素含量,分析农田环境大气颗粒中的重金属元素对农作物的影响,同时验证不同仪器工作参数对测定结果的影响。实验表明：在选定的实验条件下,分析元素的检出限低,准确性和精密度...  相似文献   

天然河床渗滤取水工艺的原理与特点研究——以浠水南城水厂为例     

宋凯  李晓  吴方燕 《地下水》2011,(1):106-108

渗滤取水净水机理主要是利用砂砾石层表面的泥膜及砂砾石层本身过滤作用、吸附作用,微生物的降解作用达到去除水中的悬浮物质、降低水的浊度、除菌的效果。以湖北浠水南城水厂渗滤取水工程为例,通过对渗滤工程特点和水质监测数据的研究,分析天然河床渗滤水水质及水源水水质的差异,以及渗滤水水质的可靠度。  相似文献   

基于越南遥感时间序列数据的湄公河三角洲土地利用及河岸变化检测研究   总被引：3，自引：0，他引：3  

阮林道  范巴赫  闵阮青  潘麦黎  蓬晃披 《资源与生态学报(英文版)》2011,(4):370-374

通过采用先进的遥感技术,基于光学和雷达时间序列卫星影像（陆地卫星,SPOT和雷达卫星）,本文对金瓯半岛（位于湄公河三角洲南部）土地覆被变化及湄公河河岸侵蚀情况进行了检测研究。鉴于金瓯半岛典型的土地覆被类型为红树林,通过对1973-2008年红树林遥感影像分析发现,近年来红树林林地面积急剧下降,超过一半的红树林已经转变为虾养殖场。与此同时,检测发现湄公河河岸已经被严重侵蚀,且侵蚀趋势正加速恶化。具体而言,田河和口河的左右两岸被认为是遭受严重侵蚀的热点区域。本文以1966-1968年地形图作为基准线数据,与1989-2009年卫星影像数据进行比照分析,此外采用数字海岸线分析系统（DSAS）模型对未来变化趋势进行了预测。  相似文献   

Purification and characterization of acetylcholinesterase from brain tissues of Oreochromis aurea and its application in environmental pesticide monitoring     

YunHua Ding  XiaoMin Wu  JunBin Fang 《寒旱区科学》2011,3(4):0339-0343

Acetylcholinesterase (AChE) plays an important role in enzyme-based detection of pesticides in the environment. In this paper, AChE from the Triton X-100 extract of brain tissues of Oreochromis aurea was purified by (NH₄)₂SO₄ fractional precipitation, Sephadex G-100 gel filtration, and DEAE-cellulose ion exchange chromatography. Certain biochemical characterizations of the purified enzyme and inhibition of pesticides on the enzyme were also studied. The specific activity of this purified enzyme was 20.628 U/mg protein, fold of purification was 139, and recovery was 22.1%. The optimal temperature of this enzyme was between 35–40 °C, and optimal pH was between 7.5–8.0. The Michaelis constant (K_m) for acetylthiocholine iodide was 0.183 mmol/L. The enzyme activity was inhibited by excess substrate, and optimal substrate concentration was 6 mmol/L. Four pesticides (dichlorvos, phoxim, triazophos, and methomyl) exhibited strong inhibitions on this enzyme with IC₅₀ less than 5 μg/mL. This study suggests that Oreochromis aurea (tilapia) could be a good enzyme source for pesticide monitoring in water environments.  相似文献   

地下水曝气-砂滤处理产生的废弃石英砂中铁砷含量与形态分布     

张耀强  胡冰冰  谢世伟  袁松虎 《地学前缘》2021,28(5):208-214

高铁高砷地下水严重威胁饮水质量,曝气-砂滤法因处理效果好且成本低在农村地区得到广泛应用。砂滤过程石英砂表面富集铁和砷后需定期更换,然而废弃石英砂堆置具有砷释放风险。本文以江汉平原某水厂砂滤池废弃石英砂为研究对象,采用激光剥蚀-等离子体质谱(LA-ICP-MS)、拉曼光谱(Raman)、X射线衍射(XRD)和分步化学提取等手段,研究了砂样中的Fe和As含量及形态分布。结果表明,砂粒表面形成了一层厚度为20100 μm的高铁砷薄层,薄层内部Fe和As含量显著高于两侧,Fe和As分布高度相关(R²=0.985)。砂样表面铁矿物以无定型/弱结晶型为主,同时检出赤铁矿和臭葱石等矿物。砂样中Fe和As总含量分别为20.1 mg/g和53.4 μg/g。砂样表面铁主要以易溶解态、碳酸盐结合态和易还原态为主,As主要吸附在铁矿物上。研究区降雨充沛,当废弃石英砂遭遇雨水冲刷或淹没时,可能导致铁砷薄层中As解吸或随Fe矿物还原溶解而释放。  相似文献   

单井水文地质参数简化计算及意义     

杨忠红  马婧 《四川地质学报》2012,(2):199-200

单井抽水试验是水文地质勘探中广泛实施的手段,其导水系数 K M 或渗透系数 K 值通常是从抽水结果的涌水量 Q 和井中水位降数据计算求得.但单井中水量的水位降深,多受井结构完善程度的制约,难以反映出井点处含水层真实的水位降.另外,在基岩含水层试验中,常以抽水井揭露所谓含水层的岩性岩层厚度作为含水层厚,这又给 K 值的确定带来一定的偏差.就日常工作中在对抽水成果整理方面所遇的一些问题提出见解,以共讨论  相似文献   

人工快速渗滤系统处理农村生活污水实验研究     

李蘅  黄伟  徐文炘  雷金勇  张静  肖筱瑜 《矿产与地质》2012,26(2):161-164

文章研究了不同渗滤介质组成的人工土柱对生活污水的处理能力,结果表明河砂＋斜发沸石＋方解石滤料对COD、NH3-N都有较高去除率,水力负荷也较高。将该组合用于农村生活污水处理工程,出水水质可以达到《城镇污水处理厂污染物排放标准》（GB18918-2002）一级A标准。  相似文献   

Dividing the algal soup: is there niche separation between native bivalves (Echyridella menziesii) and non-native Daphnia pulex in New Zealand?     

《新西兰海洋与淡水研究杂志》2012,46(1):45-59

ABSTRACT

New Zealand's native freshwater mussels (kākahi, kāeo) are considered to be in decline, yet the mechanisms driving this are unclear. The widespread establishment of highly efficient filter-feeding, non-native Daphnia in New Zealand lakes may have led to competition for algae with kākahi. We conducted a controlled laboratory experiment to determine whether differences exist in algal resources utilised by kākahi and North American Daphnia pulex. Echyridella menziesii (adults and juveniles) and D. pulex were exposed to mixed algal samples for three hours to determine whether similar algal resources were removed by the grazers. Relative to controls, both adult and juvenile E. menziesii removed a broad range of algal taxa including diatoms, green algae and filamentous species, ranging in size from 33.6 to 348.0?μm. High densities of D. pulex were unable to cause depletion of these same algae species. Our results suggest niche overlap is limited between the two grazers; E. menziesii utilises larger particles than D. pulex.  相似文献