Groundwater recharge in an arid grassland as indicated by soil chloride profile and multiple tracers          下载免费PDF全文

Tianming Huang  Zhonghe Pang  Jilai Liu  Lihe Yin  W. Mike Edmunds 《水文研究》2017,31(5):1047-1057

Previous studies have shown that shallow groundwater in arid regions is often not in equilibrium with near‐surface boundary conditions due to human activities and climate change. This is especially the case where the unsaturated zone is thick and recharge rate is limited. Under this nonequilibrium condition, the unsaturated zone solute profile plays an important role in estimating recent diffuse recharge in arid environments. This paper combines evaluation of the thick unsaturated zone with the saturated zone to investigate the groundwater recharge of a grassland in the arid western Ordos Basin, NW China, using the soil chloride profiles and multiple tracers (²H, ¹⁸O, ¹³C, ¹⁴C, and water chemistry) of groundwater. Whereas conventional water balance and Darcy flux measurements usually involve large errors in recharge estimations for arid areas, chloride mass balance has been widely and generally successfully used. The results show that the present diffuse recharge beneath the grassland is 0.11–0.32 mm/year, based on the chloride mass balance of seven soil profiles. The chloride accumulation age is approximately 2,500 years at a depth of 13 m in the unsaturated zone. The average Cl content in soil moisture in the upper 13 m of the unsaturated zone ranges from 2,842 to 7,856 mg/L, whereas the shallow groundwater Cl content ranges from 95 to 351 mg/L. The corrected ¹⁴C age of shallow groundwater ranges from 4,327 to 29,708 years. Stable isotopes show that the shallow groundwater is unrelated to modern precipitation. The shallow groundwater was recharged during the cold and wet phases of the Late Pleistocene and Holocene humid phase based on palaeoclimate, and consequently, the groundwater resources are nonrenewable. Due to the limited recharge rate and thick unsaturated zone, the present shallow groundwater has not been in hydraulic equilibrium with near‐surface boundary conditions in the past 2,500 years.  相似文献   

Fast computation of general forward gravitation problems   总被引：1，自引：0，他引：1  

Fabien Casenave  Laurent Métivier  Gwendoline Pajot-Métivier  Isabelle Panet 《Journal of Geodesy》2016,90(7):655-675

  相似文献   

A secondary sludge flow hazard induced by shallow-source seismic activity in karst mining area,Guangxi, South China: localized karstification in anticline     

Zhiyong Li  Xiguang Li  Adil S. Mohammed  Mike Vorkink  Xiaomin Yan 《Natural Hazards》2016,83(1):75-95

  相似文献   

3D geological modelling of the Renard 2 kimberlite pipe,Québec,Canada: from exploration to extraction     

L&#;pine  Isabelle  Farrow  Darrell 《Mineralogy and Petrology》2018,112(2):411-419

The Renard 2 kimberlite pipe is one of nine diamondiferous kimberlite pipes that form a cluster in the south-eastern portion of the Superior Province, Québec, Canada and is presently being extracted at the Renard Mine. It is interpreted as a diatreme-zone kimberlite consisting of two Kimberley-type pyroclastic units and related country rock breccias, all cross-cut by coherent kimberlite dykes and irregular intrusives. Renard 2 has been the subject of numerous diamond drilling campaigns since its discovery in 2001. The first two geological models modelled kimberlite and country rock breccia units separately. A change in modelling philosophy in 2009, which incorporated the emplacement envelope and history, modelled the entire intrusive event and projected the pipe shape to depth allowing for more targeted deep drilling where kimberlite had not yet been discovered. This targeted 2009 drilling resulted in a > 400% increase in the volume of the Indicated Resource. Modelling only the kimberlite units resulted in a significant underestimation of the pipe shape. Current open pit and underground mapping of the pipe shape corresponds well to the final 2015 geological model and contact changes observed are within the expected level of confidence for an Indicated Resource. This study demonstrates that a sound understanding of the geological emplacement is key to developing a reliable 3D geological and resource model that can be used for targeted delineation drilling, feasibility studies and during the initial stages of mining.

  相似文献   

A new map of glacigenic features and glacial landsystems in central mainland Nunavut,Canada     

Isabelle McMartin  Pierre-Marc Godbout  Janet E. Campbell  Tommy Tremblay  Pouran Behnia 《Boreas: An International Journal of Quaternary Research》2021,50(1):51-75

A new digital map of glacial geomorphic features and interpreted glacial landsystems was produced for an area covering ~415 000 km² in the Keewatin Sector of the Laurentide Ice Sheet (LIS) in Nunavut. The map integrates information from previous surficial geology maps and >14 000 field stations, and is significantly improved by the detailed inventory of ~152 000 glacigenic features using high-resolution ArcticDEM data and Landsat 8 imagery. From this, we identify and map coherent patterns of landform development (landsystems) between the Manitoba border and the Arctic coast, many of which are entirely new and others that are significantly modified or updated. In particular, we recognize six separate ice streams, including one probable remnant ice stream, and we delineate numerous palimpsest streamlined landscapes with associated ice-flow trends and relative ages. A continuum of relict terrains with varying basal ice thermal conditions is mapped for the first time in the ice divide migration zone between Baker Lake and Wager Bay. In addition, deglacial cold-based retreat terrains and preserved warm-based landscapes unaffected by younger glacial events have been identified. These new georeferenced, multi-scale data sets and interpreted glacial landsystems provide a comprehensive framework to strengthen reconstructions of the glacial history and dynamics of one of the largest ice domes of the LIS, identify distinct glacial sediment transport paths for applications to mineral exploration, and test numerical modelling of the LIS in support of climate change studies and long-term evolution of modern ice sheets.  相似文献   

钙华体次生有机体系的界面结晶作用研究     

董发勤  陈禹衡  代群威  郑飞  刘明学  蒋忠诚  张强  李博文  Alper Bab  Mike O''Driscoll  Andelka Plenkovic-Moraj 《中国岩溶》2021,40(1):34-43

本文总结了钙华体次生有机体系中生物群落特征和界面结晶行为,根据生物在碳酸盐沉积中的角色,将钙华体中次生有机体系的界面结晶矿化类型分为生物控制矿化沉积和生物诱导矿化沉积。分述了碳酸钙沉积矿化相关的五种生物代谢活动,讨论了生物胞外聚合物（EPS）对碳酸钙矿物晶型和形貌的影响。针对目前钙华研究中存在的问题,今后应深入研究生物体主要构成元素、生物小分子和生物体内部组织在钙华形成或退化中的作用,进一步厘清钙华体与次生有机体系的多界面溶化方式,为钙华保护修复及钙华退化治理措施提供科学依据。   相似文献   

Deep-water sediment transport patterns and basin floor topography in early rift basins: Plio-Pleistocene syn-rift of the Corinth Rift,Greece     

Martin Muravchik  Gijs A. Henstra  Gauti T. Eliassen  Rob L. Gawthorpe  Mike Leeder  Haralambos Kranis  Emmanuel Skourtsos  Julian Andrews 《Basin Research》2020,32(5):1184-1212

Our current understanding on sedimentary deep-water environments is mainly built of information obtained from tectonic settings such as passive margins and foreland basins. More observations from extensional settings are particularly needed in order to better constrain the role of active tectonics in controlling sediment pathways, depositional style and stratigraphic stacking patterns. This study focuses on the evolution of a Plio-Pleistocene deep-water sedimentary system (Rethi-Dendro Formation) and its relation to structural activity in the Amphithea fault block in the Corinth Rift, Greece. The Corinth Rift is an active extensional basin in the early stages of rift evolution, providing perfect opportunities for the study of early deep-water syn-rift deposits that are usually eroded from the rift shoulders due to erosion in mature basins like the Red Sea, North Sea and the Atlantic rifted margin. The depocentre is located at the exit of a structurally controlled sediment fairway, approximately 15 km from its main sediment source and 12 km basinwards from the basin margin coastline. Fieldwork, augmented by digital outcrop techniques (LiDAR and photogrammetry) and clast-count compositional analysis allowed identification of 16 stratigraphic units that are grouped into six types of depositional elements: A—mudstone-dominated sheets, B—conglomerate-dominated lobes, C—conglomerate channel belts and sandstone sheets, D—sandstone channel belts, E—sandstone-dominated broad shallow lobes, F—sandstone-dominated sheets with broad shallow channels. The formation represents an axial system sourced by a hinterland-fed Mavro delta, with minor contributions from a transverse system of conglomerate-dominated lobes sourced from intrabasinal highs. The results of clast compositional analysis enable precise attribution for the different sediment sources to the deep-water system and their link to other stratigraphic units in the area. Structures in the Amphithea fault block played a major role in controlling the location and orientation of sedimentary systems by modifying basin-floor gradients due to a combination of hangingwall tilt, displacement of faults internal to the depocentre and folding on top of blind growing faults. Fault activity also promoted large-scale subaqueous landslides and eventual uplift of the whole fault block.  相似文献   

Updated Characterization of Dorowa Phosphate Rock Mined in Zimbabwe     

Tumbure  Akinson  Bretherton  Mike R.  Bishop  Peter  Hedley  Mike J. 《Natural Resources Research》2020,29(3):1561-1570

Natural Resources Research - The physical and chemical characteristics of mined phosphate rock will vary temporally as the location and nature of the ore body changes and as the type of equipment...  相似文献   

雪宝顶区块流域钙华形成的生物作用研究     

董发勤  李刚  代群威  周琳  王富东  赵学钦  蒋忠诚  张强  李博文  Enrico Capezzuoli  Mike O''Driscoll  Andelka Plenkovic-Moraj 《中国岩溶》2021,40(1):11-18

钙华不仅具有重要的景观旅游价值,而且对确定区内碳酸盐沉积特征、环境演化规律及同期环境生物的作用与贡献有重要的研究意义.本文在对比国内外典型钙华特征的基础上,以黄龙和九寨沟为例,对雪宝顶区块流域内钙华的沉积特征、环境化学与生物作用进行阐述,指出了雪宝顶区块流域冷水型钙华的形成与演化是化学沉积-溶解作用、生物沉积与溶蚀作用...  相似文献   

Time to talk knowledge     

Mike Taylor 《New Zealand geographer》2019,75(2):85-92

As part of the secondary school qualification repackaging, the Ministry of Education has requested the geography education community define what constitutes their “critical body of knowledge.” In this article, I discuss three knowledge‐oriented themes focused on: (a) recent assessment trends in geography; (b) the predictive value of NCEA Level 3 geography with 100‐level success and (c) the nature of knowledge as expressed by the New Zealand Curriculum and assessment. Taken together, these themes suggest a need for a serious conversation about knowledge in school geography, as a pre‐cursor to the re‐design of the geography standards matrix.  相似文献