Chemical aspects of iron oxide coagulation in water: Laboratory studies and implications for natural systems     

Liyuan Liang  James J. Morgan 《Aquatic Sciences - Research Across Boundaries》1990,52(1):32-55

Initial coagulation rates of colloidal hematite (-Fe₂O₃) particles (diameter less than 0.1 µm) were measured experimentally in well-defined laboratory systems at constant temperature. The relative stability ratio,W, was obtained at various ionic strengths in NaCl medium and at pH values in the range from 3 to 12. ExperimentalW values ranged from 1 to 10⁴ in various systems. The results delineate the roles ofspecific andgeneralized coagulation mechanisms for iron oxides. Among the specifically-interacting species (G _ads ⁰ >G _coul ⁰ ) studied were phosphate, monomeric organic acids of various structures, and polymeric organic acids. The critical coagulation-restabilization concentrations of specifically-interacting anions (from 10^–7 to 10^–4 molar) can be compared with the general effects of non-specific electrolyte coagulants (10^–3 to 10^–1 molar). The laboratory results are interpreted with the help of a Surface Complex Formation/Diffuse Layer Model (SCF/DLM) which describes variations of interfacial charge and potential resulting from variations of coagulating species in solution. Comparison of these laboratory experiments with observations on iron behavior in estuarine and lake waters aids in understanding iron removal mechanisms and coagulation time scales in natural systems.  相似文献   

用非线性模型研究环境温度场和涡度场对台风发生、发展的影响   总被引：1，自引：0，他引：1  

杨成彬  郑祖光  王雨 《大气科学》1994,18(Z1):810-819

本文采用二维板对称高截断谱模式研究了环境温度场和偶度场对台风发生、发展的影响，指出整层平均的环境温度场的水平梯度和涡度场是影响台风重要因子。较强的环境温度汤梯度的作用类似于水平方向不均匀加热场的作用，能造成暖区上升、冷区下沉的热力直接环流，并且温度场的梯度越大，环流越强。对于整层平均的绝对涡度场而言，只有弱的正的平均绝对涡度才有利于台风的维持。  相似文献   

滇中郝家河砂岩铜矿的地球化学及其成因意义   总被引：1，自引：0，他引：1  

秦德先  马宏 《地质论评》1994,40(2):183-192

本文论术字滇中生代地层与矿区及春外围马头山组中铜的时空分布与迁移富集规律，揭示了矿床的沉积－后期叠加改造成因。成矿作用经历了同生沉积形成矿源层，后期叠加改造形成矿体的过程。后期改造中铜元素发生了大量迁移，矿质主要来自矿体之下伏紫色矿源层。  相似文献   

潜水延迟给水理论模型探讨     

谢承迪 《甘肃地质》1994,3(2):73-82

基于对失饱和带毛管与潜水流间交互作用的分析，提出了以“失水带迟后反应”模式计算延迟给水下的定降深流动①的成因方法。它能自然地解释水位、水头的Ｗａｌｔｏｎ三阶段演变规律，且拟合实测资料，具较强实用性。现行的纽曼代表性模型未能考虑延迟给水作用，因而其水位计算结果与实测线型相反．博尔顿法是经验性的，未予揭示该现象成因。本法基本上解决了上述问题。文后图示了各参变量对水头时空分布的影响。验算表明，将本法用于潜水出流试验推求含水层参数，可获更佳结果。  相似文献   

江汉平原渍涝灾害遥感的初步研究   总被引：2，自引：0，他引：2       下载免费PDF全文

喻光明 《水科学进展》1994,5(1):64-70

提出了采用遥感技术与地理信息系统结合研究渍涝灾害的方案,其内容包括:(1)信息源选择与信息处理1(2)清访机理与灾情分析;(3)灾情预报与防治决策.讨论了实施技术系统的基本功能:(1)图像与数据处理1(2)基本信息的提取与分析,(3)损失分析模型与预报模型.作为本方案论证的一部分,还介绍了笔者近期在这一领域中的部分研究成果.  相似文献   

晚石炭世腕足动物古生物地理区形成机制—环境控制论   总被引：2，自引：0，他引：2  

王成文 《吉林地质》1994,13(2):13-21

晚石炭世腕足动物地理分布以及散布过程受环境控制。在控制腕足动物地理分布的诸多环境因素中，温度是首要因素，板块构造亦具巨大影响。在腕足动物散布过程中，温度的驱赶作用，洋流的携带作用，海浸与海退等环境因素犹如传送带一样，将腕足动物（幼虫）携带到能满足其生态需要的生存、繁衍场所。腕足动物具快速散布的潜能，该潜能的发挥取决于环境。由于研究的类别以及其所处地质年代不同，各种环境因素控制作用的主次地位可能变更。这就是环境控制论的主要内容。  相似文献   

Prediction of tension crack location and riverbank erosion hazards along destabilized channels     

Stephen E. Darby  Colin R. Thorne 《地球表面变化过程与地形》1994,19(3):233-245

Riverbank erosion, associated sedimentation and land loss hazards are a land management problem of global significance and many attempts to predict the onset of riverbank instability have been made. Recently, Osman and Thorne (1988) have presented a Culmann-type analysis of the stability of steep, cohesive riverbanks; this has the potential to be a considerable improvement over previous bank stability theories, which do not account for bank geometry changes due to toe scour and lateral erosion. However, in this paper it is shown that the existing Osman-Thorne model does not properly incorporate the influence of tension cracking on bank stability since the location of the tension crack on the floodplain is indirectly determined via calculation or arbitrary specification of the tension crack depth. Furthermore, accurate determination of tension crack location is essential to the calculation of the geometry of riverbank failure blocks and hence prediction of land loss and bank sediment yield associated with riverbank instability and channel widening. In this paper, a rational, physically based method to predict the location of tension cracks on the floodplain behind the eroding bank face is presented and tested. A case study is used to illustrate the computational procedure required to apply the model. Improved estimates of failure block geometry using the new method may potentially be applied to improve predictions of bank retreat and floodplain land loss along river channels destabilized as a result of environmental change.  相似文献   

Rill erosion along the thalweg of a hillslope hollow: A case study from the cotswold hills,Central England     

M. C. Slattery  T. P. Burt  J. Boardman 《地球表面变化过程与地形》1994,19(4):377-385

Rill erosion is an important erosional form on agricultural soils in England, causing large losses of soil, particularly on cultivated slopes. This paper describes a rill system that developed in a small agricultural catchment in north Oxfordshire during the winter of 1992–93. The rill system comprised two components: a system of ‘feeder rills’ along the valley-side slopes, which were the result of flow concentration and erosion along wheelings, and a thalweg rill, which formed along a dry valley bottom as a result of surface runoff concentration from the feeder rills. Total volumetric soil loss from the rill system was 32·28 m³, equivalent to 3·01 m³, ha^?1 for the rill catchment area, or 3·91 t ha^?1. Mean discharge for the thalweg rill and feeder rills, calculated during a storm event, was 31·101s^?1 and 1·171s^?1, respectively. All flows were fully turbulent and supercritical. We emphasize the need for a spatially distributed approach to the study of runoff and erosion at the catchment scale.  相似文献   

吉林中部石炭系岩石建造及其构造环境     

贾大成  卢焱  崔圣哲 《吉林大学学报(地球科学版)》1994,(1)

吉林中部石炭系出露较全，具有独特的区域大地构造环境，在吉林晚古生代褶皱带演化中具有特殊性。本文将吉中石炭系划分为６个岩石建造，每一建造各具特征，并以岩石建造为手段，进行区域大地构造分析，认为该区石灰纪是在弧后一大陆边缘基础上形成的裂谷一拗陷带的构造环境，具有由先期裂谷发展阶段转变为末期拗陷带的演化过程，从而表明该区石炭纪为一拉张的构造历史时期。  相似文献   

斯堪的那维亚臭氧亏损和地面加热     

Zhou Libo  Zou Han  Ji Chongping  Wang Wei  Jian Yongxiao 《大气科学进展》2001,18(3):454-466

对ＮＡＳＡ的ＴＯＭＳ臭氧资料进行分析后指出：冬季在北极的斯堪的那维亚地区存在一个明显的臭氧亏损区，亏损区的中心值达－５０ ＤＵ，相当于该区域平均值的 １５％。对臭氧亏损和北大西洋海温的东西向差异作相关分析得到：其季节变化的相关系数为－０．９６，逐月（ １６８个月）变化的相关系数为－０．７０。同样对臭氧亏损与地面加热进行相关分析后指出：斯堪的那维亚地区的臭氧亏损和该地区地面的热通量关系极其密切，其相关系数均在－０．８７以上。由此我们认为：北大西洋暖流向北输送能量，引起斯堪的纳维亚地区地面加热，由此造成了冬季该地区的臭氧亏损。  相似文献