Numerical Analysis of Groundwater Ridging Processes Considering Water‐Air Flow in a Hillslope          下载免费PDF全文

Yong Ge Zang  Dong Mei Sun  Ping Feng  Stephan Semprich 《Ground water》2018,56(4):594-609

In this study, a water‐air two‐phase flow model was employed to investigate the formation, extension, and dissipation of groundwater ridging induced by recharge events in a hypothetical hillslope‐riparian zone, considering interactions between the liquid and gas phases in soil voids. The simulation results show that, after a rain begins, the groundwater table near the stream is elevated instantaneously and significantly, thereby generating a pressure gradient driving water toward both the stream (the discharge of groundwater to the stream) and upslope (the extension of groundwater ridging into upslope). Meanwhile, the airflow upslope triggered by the advancing wetting front moves downward gradually. Therefore, the extension of groundwater ridging into upslope and the downward airflow interact within a certain region. After the rain stops, groundwater ridging near the stream declines quickly while the airflow in the lower part of upslope is still moving into the hillslope. Thus, the airflow upslope mitigates the dissipation of groundwater ridging. Additionally, the development of groundwater ridging under different conditions, including rain intensity, intrinsic permeability, capillary fringe height, and initial groundwater table, was analyzed. Changes in intrinsic permeability affect the magnitude of groundwater ridging near the stream, as well as the downward speed of airflow, thereby generating highly complex responses. The capillary fringe is not a controlling factor but an influence factor on the formation of groundwater ridging, which is mainly related to the antecedent moisture. It was demonstrated that groundwater ridging also occurs where an unsaturated zone occurs above the capillary fringe with a subsurface lateral flow.  相似文献   

Transcriptomic analysis reveals the effect of the exopolysaccharide of Psychrobacter sp. B-3 on gene expression in RAW264.7 macrophage cells     

ZHANG Pingping  LI Jiang  YU Leiye  WEI Jingfang  XU Tong  SUN Guojie 《海洋学报(英文版)》2018,(8)

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南海神狐海域沉积物自生黄铁矿和石膏S同位素特征及对甲烷渗漏强度的示踪   总被引：1，自引：1，他引：0  

张美  陆红锋  管红香  刘丽华  邬黛黛  吴能友 《海洋学报(英文版)》2018,37(7):20-27

The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor environments.Anaerobic oxidation of methane(AOM) coupled with bacterial sulfate reduction results in the precipitation of solid phase minerals in seepage sediment,including pyrite and gypsum.Abundant aggregates of pyrites and gypsums are observed between the depth of 667 and 850 cm below the seafloor(cmbsf) in the entire core sediment of HS328 from the northern South China Sea.Most pyrites are tubes consisting of framboidal cores and outer crusts.Gypsum aggregates occur as rosettes and spheroids consisting of plates.Some of them grow over pyrite,indicating that gypsum precipitation postdates pyrite formation.The sulfur isotopic values(δ~(34) S) of pyrite vary greatly(from –46.6‰ to –12.3‰ V-CDT) and increase with depth.Thus,the pyrite in the shallow sediments resulted from organoclastic sulfate reduction(OSR) and is influenced by AOM with depth.The relative high abundance and δ~(34) S values of pyrite in sediments at depths from 580 to 810 cmbsf indicate that this interval is the location of a paleo-sulfate methane transition zone(SMTZ).The sulfur isotopic composition of gypsum(from–25‰ to –20.7‰) is much lower than that of the seawater sulfate,indicating the existence of a 34 S-depletion source of sulfur species that most likely are products of the oxidation of pyrites formed in OSR.Pyrite oxidation is controlled by ambient electron acceptors such as MnO_2,iron(Ⅲ) and oxygen driven by the SMTZ location shift to great depths.The δ~(34) S values of gypsum at greater depth are lower than those of the associated pyrite,revealing downward diffusion of 34 S-depleted sulfate from the mixture of oxidation of pyrite derived by OSR and the seawater sulfate.These sulfates also lead to an increase of calcium ions from the dissolution of calcium carbonate mineral,which will be favor to the formation of gypsum.Overall,the mineralogy and sulfur isotopic composition of the pyrite and gypsum suggest variable redox conditions caused by reduced seepage intensities,and the pyrite and gypsum can be a recorder of the intensity evolution of methane seepage.  相似文献   

The NE Directed Seismicity Belt in Tibet after the MS8.1 Nepal Earthquake and Its Predictive Significance     

Wang Shuangxu  Zhu Liangyu  Xu Jing  Ji Lingyun  Jiang Fengyun 《中国地震研究》2018,32(1):119-129

After the 2015 M_S8.1 Nepal earthquake, a strong and moderate seismicity belt has formed in Tibet gradually spreading along the northeast direction. In this paper, we attempt to summarize the features and investigate the primary mechanism of this behavior of seismic activity, using a 2-D finite element numerical model with tectonic dynamic settings and GPS horizontal displacements as the constraints. In addition, compared with the NE-trending seismicity belt triggered by the 1996 Xiatongmoin earthquake, we discuss the future earthquake hazard in and around Tibet. Our results show that:the NE-directed seismicity belt is the response of enhanced loading on the anisotropic Qinghai-Tibetan plateau from the Indian plate and earthquake thrusting. Also, this possibly implies that a forthcoming strong earthquake may fill in the gaps in the NE-directed seismicity belt or enhance the seismic hazard in the eastern (the north-south seismic zone) and western (Tianshan tectonic region) parts near the NE-directed belt.  相似文献   

An acoustic-wave theory for casing bond evaluation using viscoelastic slip boundary modeling     

Xiaoming Tang  Can Jiang  Yuanda Su  Xuelian Chen 《中国科学:地球科学(英文版)》2018,61(8):1057-1064

Slip boundary condition is commonly utilized to model elastic wave propagation through layered earth media. The same approach is used here to characterize acoustic wave propagation along a cased borehole with various cement bond conditions. By modeling the cement layer between casing and formation as a viscoelastic slip interface with complex coupling rigidity parameters, one can not only reduce the complexity in the classical elastic wave modeling of the problem, but also efficiently model various complicated wave phenomena that are difficult for the existing modeling. More specifically, the new theory can well describe the effect of the cement bond condition change and the location of the change (i.e., whether it is in the first interface between casing and cement, or the second interface between cement and formation) on the acoustic waves, demonstrating the good modeling capability and predicting power. Application of the theory to field data shows that the theory can correctly model the acoustic wave characteristics and interpret the cement bond condition, thus providing a useful fundament theory for casing bond evaluation using acoustic logging.  相似文献   

美国出口管制下中国外贸风险的省域地理差异     

姜辉 《地理科学》2020,40(10):1618-1626

从总贸易、出口、进口、外资和人员5个视角构建对美风险系数，测度和比较各省区市对美外贸风险的地理差异。结果表明：上海、浙江和福建与美国的进出口贸易规模最大，对美国市场的依赖程度最高，面临的综合外贸风险最大；河南尤其需要防范对美国的出口风险；海南、新疆、天津和西藏等需要加强从美国进口的风险管理；重庆除了需要防范对美出口风险外，还因为实际利用美资最多且依赖程度最大，亟需加强外资风险管理。宁夏和山西虽然从美国的引资规模不大，但是对美资的依赖程度最高，亟需提升外资多元化水平。从人员跨境流动风险来看，上海、北京和浙江面临的风险最大。中国各省区市在应对美国出口管制时应该加强外贸风险的识别和管理，针对不同的风险采取差别化的防范和化解措施。  相似文献   

通过课堂观察提升教师课程知行力的探究     

秦江 《地理教学》2020,(4):57-58,32

课堂是实施课程育人的主阵地,教师的教育观、课程观、课堂观、学生观等在课堂中的具体体现,反映了教师课程知行力的水平。本文以课程知行力的视角,探讨课堂观察的目的、内容和方法,并通过案例剖析的方式,为一线教师开展课堂观察,更新教育观念和教学方式,提升课程知行力提供参考。  相似文献   

Geological Control of Fold Structure on Gas Occurrence and Its Implication for Coalbed Gas Outburst: Case Study in the Qinan Coal Mine,Huaibei Coalfield,China     

Zhang  Kaizhong  Wang  Liang  Cheng  Yuanping  Li  Wei  Kan  Jin  Tu  Qingyi  Jiang  Jingyu 《Natural Resources Research》2020,29(2):1375-1395

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青藏高原农区农户的家庭能源消费研究     

姜璐  邢冉  陈兴鹏  薛冰 《地理科学》2020,40(3):447-454

农村能源转型是能源消费革命的重要组成部分。基于问卷调查和入户访谈,对青海省10个县（区）的318户农区家庭用能信息进行调查,辨识了青海省农区不同收入分层家庭的能源消费模式,并通过建立典型家庭能源流模型,总结了家庭能获取-消费-废弃过程的形态变化。结果显示：青海省农区家庭能源消费以煤炭、薪柴和秸秆为主,非商品能源消费占比为49.6%,清洁能源使用率低。煤炭消费在5类家庭中均占比最高,薪柴和秸秆消费在低收入家庭占比较高。高收入家庭能源消费类型更多,消费量也大,能源流动更复杂。最后,根据青海省的经济地理特征,提出相应政策建议。  相似文献   

新时期新疆水库大坝建设的主要问题与对策建议          下载免费PDF全文

李江  柳莹  刘生云  彭兆轩  吴涛 《干旱区地理》2020,43(6):1409-1416

截止 2018 年，全疆（含兵团）已建、在建及拟建水库 722 座（包括电站水库），总库容 295.0 × 10⁸ m³。有力地改善了水资源调控和利用效率，在灌溉、供水、防洪、发电、旅游等方面发挥了极其 重要的作用。新时期按照水利部“水利工程补短板、水利行业强监管”的工作总基调，针对南北疆 水资源配置不平衡问题、水资源利用不充分问题，谋划提出了兴建数十座大中型山区水库，以及提 升已建水库大坝信息化管理水平、加强水库调度运行管理，在满足生态需水的前提下统筹生活、生 产供水，最大程度发挥水库效益、确保水库安全运行。针对新时期气候变化条件下水库洪水风险 分析、大坝建设需要重点关注的几项关键技术、山区水库替代平原水库、河流健康与生态调度、水库 清淤与能力提升、水库信息化与智能调度以及延长服役期等问题进行了探讨，提出若干对策建议。  相似文献