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61.
Recent studies have focused on the relationship between solute concentrations and discharge in streams, demonstrating that concentrations can vary little relative to changes in discharge (chemostatic behaviour). Chemostatic behaviour is dependent on catchment characteristics (e.g., lithology, geomorphology, and vegetation) and chemical characteristics of the solute (e.g., availability, reactivity, and mobility). An investigation of 3 springs and a stream near Los Alamos, NM, reveals that springs can behave in a chemostatic fashion as stream systems tend to do. Another unique finding of this study is that the anthropogenic contaminants barium and the high explosive RDX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine) can also behave chemostatically. The chemostatic behaviour of a contaminant has important implications for the residence time of contaminants in a system as well as having a major control on contaminant flux and mass transport. Redox (reduction–oxidation) and biogeochemically sensitive analytes (e.g., Fe, SO4, and NO3) display a combination of chemostatic and chemodynamic behaviour, showing the influence of temporally variable conditions on stream and spring chemistries. 相似文献
62.
Stable isotope variations are extremely useful for flow partitioning within the hydrologic cycle but remain poorly understood throughout the tropics, particularly in watersheds with rapidly infiltrating soils, such as Andisols in Central America. This study examines the fluctuations of stable isotope ratios (δ18O and δ2H) in the hydrologic components of a tropical coffee agroforestry watershed (~1 km2) with Andisol soils in Costa Rica. Samples were collected in precipitation, groundwater, springs, and stream water over 2 years. The local meteoric water line for the study site was δ2H = 8.5 δ18O + 18.02 (r2 = 0.97, n = 198). The isotope ratios in precipitation exhibited an enriched trend during the dry season and a notable depletion at the beginning of the wet season. The δ18O compositions in groundwater (average = ?6.4‰, σ = 0.7) and stream water (average = ?6.7‰, σ = 0.6) were relatively stable over time, and both components exhibited more enriched values in 2013, which was the drier year. No strong correlation was observed between the isotope ratios and the precipitation amount at the event or daily time‐step, but a correlation was observed on a monthly scale. Stream water and base flow hydrograph separations based on isotope end‐member estimations showed that pre‐event water originating from base flow was prevalent. However, isotope data indicate that event water originating from springs appears to have been the primary driver of initial rises in stream flow and peak flows. These results indicate that isotope sampling improves the understanding of water balance components, even in a tropical humid location, where significant variations in rainfall challenge current modelling efforts. Further research using fine‐scale hydrometric and isotopic data would enhance understanding the processes driving spring flow generation in watersheds. 相似文献
63.
半刚性连接钢框架结构弹性时程分析 总被引:2,自引:0,他引:2
用两端带转动弹簧的杆单元代替一般的杆单元,提出了一种新的平面杆系钢结构动力弹性时程分析计算模型。采用虚功原理,通过对单元转角-位移方程的修正,推导了这种计算模型的单元质量矩阵,并编制了相应的弹性时程分析计算程序,分析了连接的半刚性在不同地震动作用下对钢框架结构动力性能的影响,并与有限元结果进行了比较。算例结果表明:连接的半刚性对结构动力性能的影响非常大,结构的抗震性能优于刚性连接的情况。 相似文献
64.
65.
66.
Hydrogeochemical Anomalies in the Springs of the Chiayi Area in West-central Taiwan as Possible Precursors to Earthquakes 总被引:1,自引:0,他引:1
S. R. Song W. Y. Ku Y. L. Chen C. M. Liu H. F. Chen P. S. Chan Y. G. Chen T. F. Yang C. H. Chen T. K. Liu M. Lee 《Pure and Applied Geophysics》2006,163(4):675-691
Water samples from both hot and artesian springs in Kuantzeling in west-central Taiwan have been collected on a regular basis
from July 15, 1999 to the end of August 2001 to measure cation and anion concentrations as a tool to detect major earthquake
precursors. The data identify chloride and sulfate ion anomalies few days prior to major quakes and lasting a few days afterward.
These anomalies are characterized by increases in Cl- concentrations from 34.9% to 41.2% and 71.5% to 138.1% as well as increases in SO42- concentrations from 232.7% to 276.8% and 100.0% to 155.1% above the means in both hot and artesian springs. The occurrence
of these anomalies is probably explained first as stress/strain-induced pressure changes in the subsurface water systems which
then generate precursory limited geochemical discharges at the levels of subsurface reservoirs. Therefore, finally leading
to the mixing of
previously separated subsurface water bodies occurs. This suggests that the hot and artesian springs in the Kuantzeling area
are possible ideal sites for recording strain changes serving well as earthquake precursors. 相似文献
67.
The present studies were carried out along the southern Mediterranean coast of Turkey, where most of the karst springs discharge
from highly karstified carbonate rocks. The case-study was applied in the Kaş-Kalkan karst region, considered one of the most
important touristic Mediterranean provinces in southern Turkey. The purpose of this study is to identify the main water resources
of the karst springs in the inland side and the expected groundwater flow paths that may recharge the coastal springs in the
study area. A comparison of the physiochemical properties and isotopic contents of the karst springs along the Kaş-Kalkan
coastline is also considered an important tool for identifying the hydrogeological characteristics and responses of the different
units in the study area. Relevant studies were carried out also considering the morphological and structural characteristics
of these karst springs and changes in their discharge amounts during the dry and wet periods.
Received: 20 August 1997 · Accepted: 2 December 1997 相似文献
68.
Fluorescent labeling of bacterial cell walls, DNA, and metabolic processes demonstrates high (potentially single molecule) sensitivity, is non-invasive, and in some cases can differentiate strains and species. Robust microscopes such as the custom instruments presented here can provide good image quality in the field and are potentially suitable for flight. However, ambiguous or false-positive results with bacterial stains can occur and can create difficulties in interpretation even on Earth. We present a “real” life detection problem in a sample of biofilms taken from the Canadian High Arctic. The samples consisted of numerous small sulfur-oxidizing bacteria and larger structures resembling fungi or diatoms. The identity of these latter structures remained ambiguous until electron microscopy and X-ray spectroscopy were performed, indicating that they were unusual sulfur minerals probably precipitated by the bacterial communities. While such mineral structures may possibly serve as biosignatures after the cells have disappeared, it is important that they not be mistaken for cells themselves. It is also possible that unusual mineral structures will be performed under extraterrestrial conditions, so great care is needed to differentiate cell structures from minerals. 相似文献
69.
S. D. Nerantzaki D. Efstathiou G. V. Giannakis M. Kritsotakis M. G. Grillakis A. G. Koutroulis 《水文科学杂志》2013,58(10):1190-1203
ABSTRACTCrete is a Mediterranean, karst-dominated island, characterized by long drought periods. The Karst-SWAT model, combined with 11 climate change scenarios, was run to assess climate change impacts on the island under two set-ups, both using the auto-irrigation function of the model: (1) with water drawn from the shallow or deep aquifer, and (2) with irrigated water derived from an unlimited outside source. The first set-up provided insight into the fluctuation of future irrigation needs, and when compared to the second set-up, enabled quantification of the future water deficit. The Water Exploitation Index was used to describe the spatial variability of future water stress on Crete. A decrease in both surface and karstic spring flows is foreseen, especially after 2060 (24.2 and 16.5%, respectively). Simulated irrigation water demand and water deficit show continuous increase throughout the projection period (2020–2098). 相似文献
70.
安徽大别山区位于扬子板块和中朝板块之间的碰撞造山带东部, 南东侧以池-太断裂为界, 北西侧止于金寨深断裂, 向东至庐江东汤池。对大别山区5个温泉, 即太湖县汤泉乡汤湾温泉(AH2)、岳西县温泉镇温泉(AH6)、岳西县菖蒲镇溪沸温泉(AH7)、庐江县东汤池温泉(AH11)和舒城县西汤池温泉(AH12)进行调查和分析。深大断裂和与之平行或斜交的小型断裂控制着大别山区温泉的出露, 地下热储带分布于花岗岩和变质花岗岩中。温泉水温为40~70℃, pH值为7~8.8, 均为中低温、弱碱性温泉。温泉氢氧稳定同位素组成表明, 大别山区温泉的补给水源为大气降水, 并具有轻微的18O漂移现象。利用同位素高程效应公式估算温泉补给区高程为950~1300 m, 补给区平均温度约为8.2℃。地下水在大别山区接受大气降水入渗补给, 经历深循环受到来自深部热源的加热之后, 沿断裂带或破碎带上升, 在山谷、河谷的低处出露形成温泉。估算的热储温度为80~120℃, 热水循环深度为1400~1800 m。结合硅焓方程法和实地调查, 认为AH2和AH7不存在冷热水混合, AH6、AH11和AH12若继续扩大开采, 不排除会发现热水与浅部冷水的混合。 相似文献