Subglacial comminution in the deforming bed: Inferences from SEM analysis     

Kathryn C. Rose  Jane K. Hart 《Sedimentary Geology》2008,203(1-2):87-97

This study investigates the variations in erosional processes beneath Briksdalsbreen; a Norwegian valley glacier, with a thin coarse grained deforming bed. The subglacial zone was investigated in situ, close to the central glacial flow line (Site A) and close to the valley wall (Site B), via boreholes. The till was collected using two different sediment samplers and the bed was examined using a borehole video camera. In order to evaluate how representative borehole sampling was of the subglacial environment, the results from in situ subglacial samples were compared with random samples taken from an exposed subglacial surface in the glacier foreland, as well as a sample taken from the site after glacier retreat. The results indicated that the texture of the exposed subglacial surface was similar to in situ samples from subglacial Site B (close to the valley wall), and that the samples collected with the ‘small’ sediment sampler had the closest fit. SEM analysis revealed eroded quartz grains at both sites as a result of rotation (abrasion) and fracture. The samples from close to the valley wall were very poorly sorted, with evidence for rounding and preservation of pre-weathered surfaces, which suggest that a relatively simple pattern of erosion from crushing to rotation dominated. However, the till from the centre of the glacier was better sorted, more angular, and with few pre-weathered surfaces. We suggest that this results from a more complex glacial erosional history associated with greater strain and longer residence time within the deforming layer. When compared with other deformation tills, it was confirmed that there is a relationship between grain size and erosional style. Clay-rich tills show little comminution, fine sand-rich tills generate a significant silt component, whilst the coarse sand-rich tills at Briksdalsbreen showed complex deformational styles but no significant silt component.  相似文献   

面向特大城市的地理国情监测框架体系建设与应用     

杨伯钢  王淼  刘博文 《北京测绘》2017,(3)

地理国情监测是时代赋予测绘地理信息部门的新使命[1]。本文从特大城市的实际需求出发,提出了一个面向特大城市的地理国情普查监测框架体系建设思路,并以北京市的应用实例,分别从框架设计、内容指标、技术体系、数据资源、基础软件、统计分析、监测应用和系统建设等方面进行阐述,可为其他特大城市地理国情监测工作的开展提供参考和借鉴。  相似文献   

A spatiotemporal indexing approach for efficient processing of big array-based climate data with MapReduce     

Zhenlong Li  Fei Hu  John L. Schnase  Daniel Q. Duffy  Tsengdar Lee  Michael K. Bowen 《International journal of geographical information science》2017,31(1):17-35

Climate observations and model simulations are producing vast amounts of array-based spatiotemporal data. Efficient processing of these data is essential for assessing global challenges such as climate change, natural disasters, and diseases. This is challenging not only because of the large data volume, but also because of the intrinsic high-dimensional nature of geoscience data. To tackle this challenge, we propose a spatiotemporal indexing approach to efficiently manage and process big climate data with MapReduce in a highly scalable environment. Using this approach, big climate data are directly stored in a Hadoop Distributed File System in its original, native file format. A spatiotemporal index is built to bridge the logical array-based data model and the physical data layout, which enables fast data retrieval when performing spatiotemporal queries. Based on the index, a data-partitioning algorithm is applied to enable MapReduce to achieve high data locality, as well as balancing the workload. The proposed indexing approach is evaluated using the National Aeronautics and Space Administration (NASA) Modern-Era Retrospective Analysis for Research and Applications (MERRA) climate reanalysis dataset. The experimental results show that the index can significantly accelerate querying and processing (~10× speedup compared to the baseline test using the same computing cluster), while keeping the index-to-data ratio small (0.0328%). The applicability of the indexing approach is demonstrated by a climate anomaly detection deployed on a NASA Hadoop cluster. This approach is also able to support efficient processing of general array-based spatiotemporal data in various geoscience domains without special configuration on a Hadoop cluster.  相似文献   

Pesticides associated with suspended sediemnts entering San Francisco Bay following the first major storm of water year 1996     

Brian A. Bergamaschi  Kathryn M. Kuivila  Miranda S. Fram 《Estuaries and Coasts》2001,24(3):368-380

Estuaries receive large quantities of suspended sediments following the first major storm of the water year. The first-flush events transport the majority of suspended sediments in any given year, and because of their relative freshness in the hydrologic system, these sediments may carry a significant amount of the sediment-associated pesticide load transported into estuaries. To characterize sediment-associated pesticides during a first-flush event, water and suspended sediment samples were collected at the head of the San Francisco Bay during the peak in suspended sediment concentration that followed the first major storm of the 1996 hydrologic year. Samples were analyzed for a variety of parameters as well as 19 pesticides and degradation products that span a wide range of hydrophobicity. Tidal mixing at the head of the estuary mixed relatively fresh suspended sediment transported down the rivers with suspended sediments in estuary waters. Segregation of the samples into groups with similar degrees of mixing between river and estuary water revealed that transport of suspended sediments from the Sacramento-San Joaquin drainage basin strongly influenced the concentration and distribution of sediment-associated pesticides entering the San Francisco Bay. The less-mixed suspended sediment contained a different distribution of pesticides than the sediments exposed to greater mixing. Temporal trends were evident in pesticide content after samples were segregated according to mixing history. These results indicate sampling strategies that collect at a low frequency or do not compare samples with similar mixing histories will not elucidate basin processes. Despite the considerable influence of mixing, a large number of pesticides were found associated with the suspended sediments. Few pesticides were found in the concurrent water samples and in concentrations much lower than predicted from equilibrium partitioning between the aqueous and sedimentary phases. The observed sediment-associated pesticide concentrations may reflect disequilibria between sedimentary and aqueous phases resulting from long equilibration times at locations where pesticides were applied, and relatively short transit times over which re-equilibration may occur.  相似文献   

砂岩储层中原油微生物降解的模拟实验研究   总被引：22，自引：2，他引：22  

陈传平  梅博文 《沉积学报》1997,15(1):135-140

模拟辽河冷东-雷家地区的砂砾岩储层条件，采用该地区的正常原油，在３０℃恒温和充氧下以及有营养元素的水溶液中，进行了原油喜氧微生物降解实验。实验表明，经微生物降解后，原油的化学组成发生了较大变化，饱和烃含量下降，沥青质、非烃含量上升；水溶液的ｐＨ值下降，并在其中检测出了有机酸，可见在微生物的代谢过程中，原油中的烃类分子被部分转化为水溶性含氧酸性产物。降解实验的油样与取自同一地区的两个重质原油饱和烃气相色谱图比较，两者在组成上极其相近，其结果说明辽河油田的重油成因，是原油遭受了喜氧微生物的降解。实验对微生物降解过程的动力学进行了初步研究。微生物对饱和烃馏分中不同化合物的降解序列为:短链正构烷烃、长链正构烷烃、异构烷烃、环状烷烃。但当各组分间的浓度发生较大变化时，降解序列会有所不同。  相似文献   

Evaluation of Hydraulic Conductivities Calculated from Multiport-Permeameter Measurements   总被引：4，自引：0，他引：4  

Steven H. Wolf  Michael A. Celia  Kathryn M. Hess 《Ground water》1991,29(4):516-525

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The future of the past at Göreme in Turkey     

Robert Bowen 《Environmental Geology》1990,16(1):35-41

The structural conservation project at the Göreme circus, with its rock-hewn churches, is a program for safeguarding this area in Cappadocia. The aim of this paper is to inquire into the causes of observed degradation and define a general plan of intervention which associates processes controlling the development of the phenomena with appropriate repair technologies facilitating treatment of the most urgent cases of damage. The first problem noted is clearly erosion. To natural erosion must be added the effects of localized erosion resulting from increasing tourism on the site. The second difficulty is to be seen in fissuring and fracturing in the soft rock, a volcanic tuff. Treatment of fissures in domes involves complete covering of the rock. Also, it must be noted that low-pressure injection grouting with a product suitable for the fissures would assure water-tightness of the monument and restore to the massif its monolithic stability.  相似文献   

矿区水文地质研究进展及中长期发展方向   总被引：2，自引：0，他引：2  

张发旺  陈立  王滨  么红超  许柏青  李敏巍  胡博文  钱龙 《地质学报》2016,90(9):2464-2475

矿区水资源保护和矿山防治水这两个互相矛盾又紧密联系的问题给传统的矿山水文地质学带来了更多的挑战和机遇,迫切需要新理论、新技术的发展。为了更好的实现矿区未来地下水资源的开采、利用与保护以及采煤安全和区域水资源可持续利用,本文选择长治盆地为重点研究区,从采动引起的覆岩移动入手,在资料分析的基础上,采用相似材料模拟、综合物探、野外监测、现场注(压)水试验的方法,运用水文地质学原理研究了采煤引起含水层结构变异厚度及其渗透性变化特征;在此基础上,以长治盆地集中开采区水文地质条件和野外监测数据为基础,建立了区域地下水流场三维动态模拟试验台,为研究含水层结构变异后的地下水循环机理和水资源重新分布提供技术支撑;本文同时指出了我国矿山水文地质研究目前存在的问题和面临的挑战,分析了矿山水文地质学科的发展趋势,展望了未来相关分支学科和关键核心技术的发展方向与前景。  相似文献   

Early middle Miocene tectonic uplift of the northwestern part of the Qinghai–Tibetan Plateau evidenced by geochemical and mineralogical records in the western Tarim Basin     

Chaowen Wang  Hanlie Hong  Hemmo A. Abels  Zhaohui Li  Kai Cao  Ke Yin  Bowen Song  Yadong Xu  Junliang Ji  Kexin Zhang 《International Journal of Earth Sciences》2016,105(3):1021-1037

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Removal of fluoride ion from groundwater by adsorption on lanthanum and aluminum loaded clay adsorbent     

Shengyu Zhang  Ying Lyu  Xiaosi Su  Yuya Bian  Bowen Yu  Yuling Zhang 《Environmental Earth Sciences》2016,75(5):401

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