首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7篇
  免费   1篇
地球物理   5篇
地质学   3篇
  2020年   1篇
  2016年   1篇
  2012年   1篇
  2010年   1篇
  2008年   2篇
  2004年   1篇
  1966年   1篇
排序方式: 共有8条查询结果,搜索用时 15 毫秒
1
1.
The link between spatiotemporal patterns of stream water chemistry and catchment characteristics for the mesoscale Dill catchment (692 km2) in Germany is explored to assess the catchment scale controls on water quality and to characterize water sources. In order to record the spatiotemporal pattern, ‘snapshot sampling’ was applied during low, mean and high flow, including 73 nested sites throughout the catchment. Water samples were analysed for the elements Li, B, Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Mo, Ba, Pb and U using inductively‐coupled‐plasma mass spectrometry, and for electric conductivity and pH. Principle component analysis and hierarchical cluster analysis were used to find typical element associations and to group water samples according to their hydrochemical fingerprints. This revealed regional hydrochemical patterns of water quality which were subsequently related to catchment attributes to draw conclusions about the controls on stream chemistry. It was found that various lithologic signals and anthropogenic point source inputs controlled the base flow hydrochemistry. During increased flows, stream waters were diluted causing additional hydrochemical variability in response to heterogeneous precipitation inputs and differences in aquifer storage capacities. The hydrochemical patterns further displayed in‐stream mixing of waters. This implied, that stream waters could be apportioned to the identified water sources throughout the catchment. The basin‐wide hydrochemical variability has the potential to outrange the tracer signatures typically inferred in studies at the hillslope scale and is able to strongly influence the complexity of the catchment output. Both have to be considered for further catchment scale tracer and modelling work. Despite the likelihood of non‐conservative behaviour, the minor and trace elements enhanced the rather qualitative discrimination of the various groundwater types, as the major cations were strongly masked by point source inputs. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
2.
In this study, the Mean Transit Time and Mixing Model Analysis methods are combined to unravel the runoff generation process of the San Francisco River basin (73.5 km2) situated on the Amazonian side of the Cordillera Real in the southernmost Andes of Ecuador. The montane basin is covered with cloud forest, sub‐páramo, pasture and ferns. Nested sampling was applied for the collection of streamwater samples and discharge measurements in the main tributaries and outlet of the basin, and for the collection of soil and rock water samples. Weekly to biweekly water grab samples were taken at all stations in the period April 2007–November 2008. Hydrometric data, Mean Transit Time and Mixing Model Analysis allowed preliminary evaluation of the processes controlling the runoff in the San Francisco River basin. Results suggest that flow during dry conditions mainly consists of lateral flow through the C‐horizon and cracks in the top weathered bedrock layer, and that all subcatchments have an important contribution of this deep water to runoff, no matter whether pristine or deforested. During normal to low precipitation intensities, when antecedent soil moisture conditions favour water infiltration, vertical flow paths to deeper soil horizons with subsequent lateral subsurface flow contribute most to streamflow. Under wet conditions in forested catchments, streamflow is controlled by near surface lateral flow through the organic horizon. Exceptionally, saturation excess overland flow occurs. By absence of the litter layer in pasture, streamflow under wet conditions originates from the A horizon, and overland flow. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
3.
We investigated controls on the water chemistry of a South Ecuadorian cloud forest catchment which is partly pristine, and partly converted to extensive pasture. From April 2007 to May 2008 water samples were taken weekly to biweekly at nine different subcatchments, and were screened for differences in electric conductivity, pH, anion, as well as element composition. A principal component analysis was conducted to reduce dimensionality of the data set and define major factors explaining variation in the data. Three main factors were isolated by a subset of 10 elements (Ca2+, Ce, Gd, K+, Mg2+, Na+, Nd, Rb, Sr, Y), explaining around 90% of the data variation. Land-use was the major factor controlling and changing water chemistry of the subcatchments. A second factor was associated with the concentration of rare earth elements in water, presumably highlighting other anthropogenic influences such as gravel excavation or road construction. Around 12% of the variation was explained by the third component, which was defined by the occurrence of Rb and K and represents the influence of vegetation dynamics on element accumulation and wash-out. Comparison of base- and fast flow concentrations led to the assumption that a significant portion of soil water from around 30 cm depth contributes to storm flow, as revealed by increased rare earth element concentrations in fast flow samples. Our findings demonstrate the utility of multi-tracer principal component analysis to study tropical headwater streams, and emphasize the need for effective land management in cloud forest catchments.  相似文献   
4.
Traditional Boussinesq or kinematic simulations of interflow (i.e., lateral subsurface flow) assume no leakage through the impeding layer and require a no-flow boundary condition at the ridge top. However, recent analyses of many interflow-producing landscapes indicate that leaky impeding layers are common, that most interflow percolates well before reaching the toe slope, and therefore, the downslope contributing length is shorter than the hillslope length. In watersheds characterised by perched interflow over a low conductivity layer through permeable topsoil, interflow with percolation may be modelled with a kinematic wave model using a mobile upslope boundary condition defining the hillslope portion contributing interflow to valleys. Here, we developed and applied a dynamic interflow model to simulate interflow using a downslope travel distance concept such that only the active contributing length is modelled at any time. The model defines a variable active area based on the depth of the perched layer, the topographic slope and the ratio of the hydraulic conductivity of topsoil to that of the impeding layer. It incorporates a two-layer soil moisture accounting water balance analysis, a pedo-transfer function, and percolation and evaporation routines to predict interflow rates in continuous and event-based scenarios. We tested the modelling concept on two sets of data (2-year dataset of rainfall observations for the continuous simulation and a multi-day irrigation experiment for the event simulation) from a 121-m-long open interflow collection trench on an experimental hillslope at the Savannah River Site, South Carolina. The continuous model simulation partially represented the observed interflow hydrograph and perched water depth in the experimental hillslope with correlation coefficients of 0.85 and 0.35, respectively. Model performance improved significantly at event-scale analysis. The modelling approach realistically represents interflow dynamics in hillslopes with leaky impeding layers and can be integrated into catchment-scale hydrology models for more detailed hillslope process modelling.  相似文献   
5.
Few high‐elevation tropical catchments worldwide are gauged, and even fewer are studied using combined hydrometric and isotopic data. Consequently, we lack information needed to understand processes governing rainfall–runoff dynamics and to predict their influence on downstream ecosystem functioning. To address this need, we present a combination of hydrometric and water stable isotopic observations in the wet Andean páramo ecosystem of the Zhurucay Ecohydrological Observatory (7.53 km2). The catchment is located in the Andes of south Ecuador between 3400 and 3900 m a.s.l. Water samples for stable isotopic analysis were collected during 2 years (May 2011–May 2013), while rainfall and runoff measurements were continuously recorded since late 2010. The isotopic data reveal that andosol soils predominantly situated on hillslopes drain laterally to histosols (Andean páramo wetlands) mainly located at the valley bottom. Histosols, in turn, feed water to creeks and small rivers throughout the year, establishing hydrologic connectivity between wetlands and the drainage network. Runoff is primarily composed of pre‐event water stored in the histosols, which is replenished by rainfall that infiltrates through the andosols. Contributions from the mineral horizon and the top of the fractured bedrock are small and only seem to influence discharge in small catchments during low flow generation (non‐exceedance flows < Q35). Variations in source contributions are controlled by antecedent soil moisture, rainfall intensity, and duration of rainy periods. Saturated hydraulic conductivity of the soils, higher than the year‐round low precipitation intensity, indicates that Hortonian overland flow rarely occurs during high‐intensity precipitation events. Deep groundwater contributions to discharge seem to be minimal. These results suggest that, in this high‐elevation tropical ecosystem, (1) subsurface flow is a dominant hydrological process and (2) (histosols) wetlands are the major source of stream runoff. Our study highlights that detailed isotopic characterization during short time periods provides valuable information about ecohydrological processes in regions where very few basins are gauged. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
6.
Atmospheric precipitation samples were collected in the Bohemian Karst (30 km SW from Prague, Czech Republic) at six localities in the vicinity of the limestone-quarry Čertovy schody during years 1996–2003. Samples were analyzed for major components (Na+, K+, Mg2+, Ca2+, F, Cl, NO3, HCO3, SO42−) and trace metals (Cu, Mn, Fe, Zn, Pb, Be, As, Sr, Cd, Al, Cr). Deposition fluxes were calculated from more than 10 000 elemental analyses of samples collected monthly. The fluxes of monitored substances show temporal and spatial variability. The most marked attribute is the strong affection by local emission sources confirmed by the investigation of seasonal variability, temporal trend and correlation analysis.  相似文献   
7.
Zusammenfassung Im südanatolischen Taurus wurden während des Paläozoikums in einer Orthogeo synklinale Sedimente in weitgehender fazieller und faunistischer Übereinstimmung mit der Entwicklung in Mittel- und Südosteuropa abgelagert. Durch Faltungen, Regionalmetamorphose und Magmentätigkeit, welche sich innerhalb des Zeitraums vom Mitteldevon bis zum Unteren Jura ereigneten, entstanden im Taurus Massive mit variszischer Konsolidierung. An den variszischen Magmenzyclus sind entsprechende Erzlagerstätten gebunden. Der initiale Vulkanismus im Mittel- und Oberdevon lieferte Roteisen- und Blei-Zinklagerstätten. Im Zusammenhang mit dem subsequenten Vulkanismus in Oberperm und Untertrias stehen Blei-Zinklagerstätten mit schwerspätig-kalkspätiger Gangart. Im Gefolge des spättektonischen Plutonismus entstanden zuletzt in der Trias Skarnlagerstätten des Eisens.
During the paleozoic period a deposition of sediments corresponding to the evolution of facies and fauna in middle and southeastern Europe took place in the south-anatolian Taurus. Folding, regional metamorphism and magmatic activity, which happened in the period from Middle Devonian to Lower Jurassic, formed intratauridic massives with hercynian consolidation. In connexion to the magmatic cycle occur some characteristic groups of ore deposits. The initial vulcanism during middle-upper devonian period produced hematite and lead-zinc deposits. Together with the subsequent vulcanism of the Upper Permian and Lower Triassic occurred lead-zinc-barite deposits. The late tectonic plutonism in the Triassic formed scarn deposits of iron ores.
  相似文献   
8.
An attempt to indicate the sources and pathways of selected chemical substances in precipitation over central Bohemia was accomplished with help of bulk samples, collected in a forested rural landscape approx. 30 km SE from Prague, capital of the Czech Republic. Samples have been collected monthly throughout the 1990s. They were analyzed to determine the concentration of selected major cations and anions (Na+, K+, Ca2+, Mg2+, NH4 +, SO4 2-, NO3 -, Cl-), as well as several minor and trace elements (Al, As, Be, Cd, Cu, Fe, Mn, Pb, Sr, Zn, F-).Set of the bulk samples shows strong mutual correlation of the main acidifiers - compounds of N, S (and F). Good correlation occurs also at the typical lithogenic elements Al, K, Na, Ca, Mg, Sr, and the typical elements originating from the flue gases of the combustion chambers burning low quality brown coal - As, (Be), Cd, Cu, Pb, and Zn. The only strong correlation of Cl with Na (and Mg) indicates that majority of these elements originates from the oceanic spray. The content of pollutants in precipitation depends on the air masses types and on the rout of their approach to the sampling site. The typing of synoptic situations was employed for the determination of the air masses types and routs and of the corresponding fronts and precipitation fields.  相似文献   
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号