THE ROLE OF STANDING WATER AND WATER-LOGGED SOILS IN RAISED-FIELD, DRAINED-FIELD AND ISLAND-BED AGRICULTURE     

D. E. Vasey  A.B.  Ph.D.    D. R. Harris  Ph.D.    G. W. Olson  Ph.D.    M. J. T. Spriggs  Ph.D.  B. L. Turner II  Ph.D. 《Singapore journal of tropical geography》1984,5(1):63-72

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Linking snowmelt‐derived fluxes and groundwater flow in a high elevation meadow system,Sierra Nevada Mountains,California     

Christopher S. Lowry  Jeffrey S. Deems  Steven P. Loheide II  Jessica D. Lundquist 《水文研究》2010,24(20):2821-2833

Quantifying snowmelt‐derived fluxes at the watershed scale within hillslope environments is critical for investigating local meadow scale groundwater dynamics in high elevation riparian ecosystems. In this article, we investigate the impact of snowmelt‐derived groundwater flux from the surrounding hillslopes on water table dynamics in Tuolumne Meadows, which is located in the Sierra Nevada Mountains of California, USA. Results show water levels within the meadow are controlled by a combination of fluxes at the hillslope boundaries, snowmelt within the meadow and changes in the stream stage. Observed water level fluctuations at the boundaries of the meadow show the hydrologic connection and subsequent disconnection between the hillslope and meadow aquifers. Timing of groundwater flux entering the meadow as a result of spring snowmelt can vary over 20 days based on the location, aspect, and local geology of the contributing area within the larger watershed. Identifying this temporal and spatial variability in flux entering the meadow is critical for simulating changes in water levels within the meadow. Model results can vary significantly based on the temporal and spatial scales at which watershed processes are linked to local processes within the meadow causing errors when boundary fluxes are lumped in time or space. Without a clear understanding of the surrounding hillslope hydrology, it is difficult to simulate groundwater dynamics within high elevation riparian ecosystems with the accuracy necessary for understanding ecosystem response. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Mineralogy and environmental geochemistry of historical iron slag,Hopewell Furnace National Historic Site,Pennsylvania, USA     

Nadine M. Piatak  Robert R. Seal II 《Applied Geochemistry》2012

The Hopewell Furnace National Historic Site in southeastern Pennsylvania, which features an Fe smelter that was operational in the 18th and 19th centuries, is dominated by three slag piles. Pile 1 slag, from the Hopewell Furnace, and pile 2 slag, likely from the nearby Cornwall Furnace, were both produced in cold-blast charcoal-fired smelters. In contrast, pile 3 slag was produced in an anthracite furnace. Ore samples from the nearby Jones and Hopewell mines that fed the smelter are mainly magnetite-rich with some sulfides (pyrite, chalcopyrite, sphalerite) and accessory silicates (quartz, garnet, feldspar, and clay minerals). Slag piles 1 and 2 are similar mineralogically containing predominantly skeletal and dendritic aluminian diopside and augite, skeletal forsteritic olivine, glass, rounded blebs of metallic Fe, and exotic quartz. Olivine is a major phase in all samples from pile 2, whereas it occurs in only a few samples from pile 1. Samples of the <2 mm-size fraction of surface composite slag material or crushed slag from at depth in piles 1 and 2 are mineralogically similar to the large surface slag fragments from those piles with the addition of phases such as feldspars, Fe oxides, and clay minerals that are either secondary weathering products or entrained from the underlying bedrock. Pile 3 slag contains mostly skeletal forsteritic olivine and Ti-bearing aluminian diopside, dendritic or fine-grained subhedral melilite, glass, euhedral spinel, metallic Fe, alabandite–oldhamite solid solution, as well as a sparse Ti carbonitride phase. The bulk chemistry of the slag is dominated by Al₂O₃ (8.5–16.2 wt.%), CaO (8.2–26.2 wt.%), MgO (4.2–24.7 wt.%), and SiO₂ (36.4–59.8 wt.%), constituting between 81% and 97% of the mass of the samples. Piles 1 and 2 are chemically similar; pile 1 slag overall contains the highest Fe₂O₃, K₂O and MnO, and the lowest MgO concentrations. Pile 3 slag is high in Al₂O₃, CaO and S, and low in Fe₂O₃, K₂O and SiO₂ compared to the other piles. In general, piles 1 and 2 are chemically similar to each other, whereas pile 3 is distinct – a conclusion that reflects their mineralogy. The similarities and differences among piles in terms of mineralogy and major element chemistry result from the different smelting conditions under which the slag formed and include the fuel source, the composition of the ore and flux, the type of blast (cold versus hot), which affects the furnace temperature, and other beneficiation methods.  相似文献   

A framework for understanding the hydroecology of impacted wet meadows in the Sierra Nevada and Cascade Ranges, California, USA   总被引：1，自引：0，他引：1  

Steven P. Loheide II  Richard S. Deitchman  David J. Cooper  Evan C. Wolf  Christopher T. Hammersmark  Jessica D. Lundquist 《Hydrogeology Journal》2009,17(1):229-246

Meadows of the Sierra Nevada and Cascade mountains of California, USA, support diverse and highly productive wet-meadow vegetation dominated by sedges, rushes, grasses, and other herbaceous species. These groundwater–dependent ecosystems rely on the persistence of a shallow water table throughout the dry summer. Case studies of Bear Creek, Last Chance, and Tuolumne meadow ecosystems are used to create a conceptual framework describing groundwater–ecosystem connections in this environment. The water requirements for wet-meadow vegetation at each site are represented as a water-table-depth hydrograph; however, these hydrographs were found to vary among sites. Causes of this variation include (1) differences in soil texture, which govern capillary effects and availability of vadose water and (2) elevation-controlled differences in climate that affect the phenology of the vegetation. The field observations show that spatial variation of water-table depth exerts strong control on vegetation composition and spatial patterning. Groundwater-flow modeling demonstrates that lower hydraulic-conductivity meadow sediments, higher groundwater-inflow rates, and a higher ratio of lateral to basal-groundwater inflow all encourage the persistence of a high water table and wet-meadow vegetation, particularly at the margin of the meadow, even in cases with moderate stream incision.  相似文献   

Lithospheric structure and tectonics at Isidis Planitia, Mars     

J. Andreas Ritzer  Steven A. Hauck II 《Icarus》2009,201(2):528-539

We characterize the lithospheric structure of Isidis Planitia on Mars by analyzing Mars Global Surveyor and Mars Odyssey gravity and topography data using a flexural model of a thin elastic shell including bending and membrane stresses. Isidis Planitia is a circular, relatively flat plain formed near the end of the Early Noachian, at the edge of the highlands-lowlands boundary and the site of a large free-air gravity anomaly, features consistent with modification and filling of an impact basin. Our results suggest that the bulk density of the fill material inside Isidis must be more than 2600 kg m⁻³ and higher densities are probable. A comparison of the faulting observed at Nili Fossae to the predicted zone of extensional strain northwest of Isidis constrains the thickness of the elastic lithosphere to be 100-180 km thick beneath the basin at the time of loading. We also find that loads outside of the basin play a significant role in the interpretation of the tectonics; simplified models tend to overestimate the lithospheric thickness. We place relatively narrow bounds on the thermal gradient (3.4-6.5 K km⁻¹) and heat flux (13.6-26 mW m⁻²) at Isidis at the time of loading.  相似文献   

Despinning plus global contraction and the orientation of lobate scarps on Mercury: Predictions for MESSENGER     

Andrew J. Dombard  Steven A. Hauck II 《Icarus》2008,198(1):274-276

Observations by the Mariner 10 spacecraft suggest that the lobate scarps on Mercury, which have been interpreted to record at most 1-2 km of radial contraction of the planet after the end of the Late Heavy Bombardment, possess a global, preferred N-S orientation but lack a strong latitudinal dependence on their surface expression. Here, we reexamine the idea that a decrease in the planetary rotation rate (despinning) coupled with global contraction of at least 3-5.5 km prior to the end of Late Heavy Bombardment resulted in global N-S oriented thrust faults. The surface expression of these faults is assumed to have been erased by the end of the Late Heavy Bombardment, and the faults were subsequently reactivated by later global contraction, producing generally N-S oriented thrust faults from an isotropic stress field. We use the estimate of >3-5.5 km contraction prior to ∼4 Ga as an additional constraint to thermomechanical simulations of the evolution of Mercury, finding that a wide range of models are consistent with this observation. The fact that a wide range of states are consistent with the contraction of Mercury prior to the end of Late Heavy Bombardment but only a restricted set of states are consistent with the at most 1-2 km of subsequent contraction bolsters the idea that there may be hidden strain on Mercury, features unseen by Mariner 10 but likely visible to the MESSENGER spacecraft.  相似文献   

Adsorption of l-aspartate to rutile (α-TiO₂): Experimental and theoretical surface complexation studies     

Caroline M. Jonsson  Christopher L. Jonsson  Charlene Estrada  Dimitri A. Sverjensky  H. James Cleaves II 《Geochimica et cosmochimica acta》2010,74(8):2356-22386

Interactions between aqueous amino acids and mineral surfaces influence many geochemical processes from biomineralization to the origin of life. However, the specific reactions involved and the attachment mechanisms are mostly unknown. We have studied the adsorption of l-aspartate on the surface of rutile (α-TiO₂, pH_PPZC = 5.4) in NaCl(aq) over a wide range of pH, ligand-to-solid ratio and ionic strength, using potentiometric titrations and batch adsorption experiments. The adsorption is favored below pH 6 with a maximum of 1.2 μmol of adsorbed aspartate per m² of rutile at pH 4 in our experiments. The adsorption decreases at higher pH because the negatively charged aspartate molecule is repelled by the negatively charged rutile surface above pH_PPZC. At pH values of 3-5, aspartate adsorption increases with decreasing ionic strength. The adsorption of aspartate on rutile is very similar to that previously published for glutamate (Jonsson et al., 2009). An extended triple-layer model was used to provide a quantitative thermodynamic characterization of the aspartate adsorption data. Two reaction stoichiometries identical in reaction stoichiometry to those for glutamate were needed. At low surface coverages, aspartate, like glutamate, may form a bridging-bidentate surface species binding through both carboxyl groups, i.e. “lying down” on the rutile surface. At high surface coverages, the reaction stoichiometry for aspartate was interpreted differently compared to glutamate: it likely involves an outer-sphere or hydrogen bonded aspartate surface species, as opposed to a partly inner-sphere complex for glutamate. Both the proposed aspartate species are qualitatively consistent with previously published ATR-FTIR spectroscopic results for aspartate on amorphous titanium dioxide. The surface complexation model for aspartate was tested against experimental data for the potentiometric titration of aspartate in the presence of rutile. In addition, the model correctly predicted a decrease of the isoelectric point with increased aspartate concentration consistent with previously published studies of the aspartate-anatase system. Prediction of the surface speciation of aspartate on rutile indicates that the relative proportions of the two complexes are a strong function of environmental conditions, which should be taken into account in considerations of geochemical systems involving the interactions of biomolecules and minerals in electrolyte solutions.  相似文献   

Reply to comment on “A framework for understanding the hydroecology of impacted wet meadows in the Sierra Nevada and Cascade Ranges, California, USA”: paper published in Hydrogeology Journal (2009) 17:229–246, by Steven P. Loheide II, Richard S. Deitchman, David J. Cooper, Evan C. Wolf, Christopher T. Hammersmark, Jessica D. Lundquist     

Steven P. Loheide II  Richard S. Deitchman  David J. Cooper  Evan C. Wolf  Christopher T. Hammersmark  Jessica D. Lundquist 《Hydrogeology Journal》2010,18(7):1745-1746

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Wollastonite at the Sterling Hill Fe–Zn–Mn ore body, Ogdensburg, New Jersey     

A. Dúzs-Moore  P. B. Leavens  R. E. Jenkins II  N. M. Altounian 《Mineralogy and Petrology》2003,79(3-4):225-241

Summary Wollastonite occurs abundantly at the Sterling Hill Fe–Zn–Mn ore deposit, Ogdensburg, New Jersey, one of the few occurrences of wollastonite in regionally metamorphosed rocks; it is absent from the surrounding Franklin marble. Wollastonite occurs in two distinct bands along the inner margins of the synclinal ore deposit. Minerals associated with wollastonite include calcite, grossular-andradite, diopsidic pyroxene, alkali feldspar, and rarely vesuvianite, quartz or bustamite. Assuming the generally accepted values of 750°C at 5kbar at Sterling Hill during metamorphism in the Grenville Orogeny, thermodynamic modeling of reactions involving garnet and wollastonite suggest XCO₂ 0.35 in the wollastonite-bearing rocks. Infiltrating metamorphic fluid rich in H₂O was necessary for the formation of wollastonite; at XCO₂ of 0.35, the calculated minimum volumetric water:rock ratio is 0.51. The source of the water is believed to be the dehydration of water-rich phases in adjacent ores or mafic rocks. The chemical compositions, textures, stratigraphy, and calculated metamorphic conditions show that wollastonite formed from calcite and quartz at the peak of the Grenville Orogeny.Present address: Maryland State Highway AdministrationReceived August 18, 2002; revised version accepted February 5, 2003  相似文献   

黑龙江五大连池火山群地壳电性结构   总被引：11，自引：3，他引：11  

詹艳赵国泽  王继军肖骑彬  汤吉Rokityansky П 《岩石学报》2006,22(6):1494-1502

对1997年在黑龙江五大莲池火山群观测的7条大地电磁测深剖面资料进行重新处理，对全部测点的实、虚感应矢量和视电阻率曲线等参数的分布特征进行了详细分析，应用NLCG二维反演方法对3条近东西向剖面数据进行了反演，获得的深部电性结构结果显示：五大莲池火山群中的笔架山-老黑山-火烧山火山链上的火山规模明显大于南、北格拉球火山链和东、西焦得布火山链，该带火山活动有从南西向北东推移的规律；以笔架山-老黑山-火烧山火山链为中心在地下约几百米深度到20km左右，存在一个北北东走向、上宽下窄、北宽南窄似铆钉的状体，该块体随着深度的增加其电阻率值从上千欧姆米逐渐减小到小于1欧姆米；在深度约20km以下铆钉的主体仍然显示有向深处延伸的趋势，推测一直穿过地壳与上地幔连接；在深度4～8km左右火烧山、老黑山和笔架山东、西两侧存在低阻块体；结合S波速度、小震活动以及地热研究结果分析，推测笔架山-老黑山-火烧山火山链在地壳内随着深度增大存在不同凝固程度的岩浆系统。  相似文献