Ground-Water Problems in the Mesozoic Pax Mountain Fault Zone     

David S. Snipes  Peter R. Manoogian  Michael W. Davis  Laura L. Burnett  Jerry A. Wylie  Steven B. Heaton 《Ground water》1986,24(3):375-381

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ISOTOPES IN GROUND-WATER INVESTIGATIONS     

Laura Toran 《Ground water》1982,20(6):740-745

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Graben width controlling syn-rift sedimentation: the Palaeogene southern Upper Rhine Graben as an example     

Sebastian Hinsken  Kamil Ustaszewski  Andreas Wetzel 《International Journal of Earth Sciences》2007,96(6):979-1002

Eocene to Early Oligocene syn-rift deposits of the southern Upper Rhine Graben (URG) accumulated in restricted environments. Sedimentation was controlled by local clastic supply from the graben flanks, as well as by strong intra-basinal variations in accommodation space due to differential tectonic subsidence, that in turn led to pronounced lateral variations in depositional environment. Three large-scale cycles of intensified evaporite sedimentation were interrupted by temporary changes towards brackish or freshwater conditions. They form three major base level cycles that can be traced throughout the basin, each of them representing a stratigraphic sub-unit. A relatively constant amount of horizontal extension (ΔL) in the range of 4–5 km has been estimated for the URG from numerous cross-sections. The width of the rift (L _f ), however, varies between 35 and more than 60 km, resulting in a variable crustal stretching factor between the bounding masterfaults. Apart from block tilting, tectonic subsidence was, therefore, largely controlled by changes in the initial rift width (L ₀). The along-strike variations of the graben width are responsible for the development of a deep, trough-like evaporite basin (Potash Basin) in the narrowest part of the southern URG, adjacent to shallow areas in the wider parts of the rift such as the Colmar Swell in the north and the Rhine Bresse Transfer Zone that delimits the URG to the south. Under a constant amount of extension, the along-strike variation in rift width is the principal factor controlling depo-centre development in extensional basins.  相似文献   

Free cupric ion concentrations and Cu complexation in selected Swiss lakes and rivers   总被引：1，自引：0，他引：1  

Hanbin Xue  Andrea Oestreich  David Kistler  Laura Sigg 《Aquatic Sciences - Research Across Boundaries》1996,58(1):69-87

[Cu²⁺] and Cu complexation parameters in some selected freshwater systems in Switzerland were determined by the technique of ligand-exchange and DPCSV. Results from the water columns of some eutrophic and oligotrophic lakes are presented and compared to small acid lakes. Cu is strongly complexed by organic ligands which with very high stability constants at low concentrations are probably biologically produced, as indicated by the seasonal variations in the eutrophic lakes and by the relationship between Cu complexation and algal activity in the eutrophic (pCu=15–16), oligotrophic (pCu=13–14) and acidic (pCu=9–10) lakes. The extent of Cu complexation in river waters was generally lower than in the eutrophic lakes, at similar DOC levels. No obvious correlation between Cu complexation and DOC was observed, indicating that Cu complexing ligands are specific organic compounds.  相似文献   

A metabolism-based trophic index for comparing the ecological values of shallow-water sediment habitats     

W. M. Rizzo  S. K. Dailey  G. J. Lackey  R. R. Christian  B. E. Berry  R. L. Wetzel 《Estuaries and Coasts》1996,19(2):247-256

We determined fluxes of oxygen and nutrients between water and sediments at 21 sites primarily in Virginia and North Carolina estuaries, over the past 15 yr. These sites represented broad ranges in salinity, tidal amplitude, hydrology, nutrient availability, turbidity, light availability, depth, sediment grain size, and anthropogenic disturbance. In general, we found that heterotrophically dominated sediments had the potential to degrade water quality, whereas photoautotrophy in the sediments ameliorated this impact. We propose a benthic trophic state index as a management tool to make general assessments of the degree to which sediments support ecological processes related to photoautotrophy. The index can be based on simple measurements of metabolic parameters. We also evaluated the relative significance of variability in the index across a number of spatial and temporal scales. Reduced photoautotrophy and/or enhanced heterotrophy tended to be associated with finer-grained, organic-rich sediments. This sediment type was common in oligohaline areas at water depths exceeding 2 m. Temporally, autotrophy declined from winter to spring particularly at sandy sites, while interannual variability was more pronounced for mud sites. *** DIRECT SUPPORT *** A01BY074 00011  相似文献   

雅鲁藏布中新生代深水沉积盆地形成和演化(Ⅰ)——喜马拉雅造山带沉积特征及演化          下载免费PDF全文

刘宝珺  余光明  徐强  G. Einsele  W. Frisch  刘光华  J. Wendt  A. Wetzel  L. Ratschbacher  H. P. Luterbacher 《沉积与特提斯地质》1993,(1):32-49

通过对喜马拉雅三叠纪到第三纪区域沉积特征分析,阐明了雅鲁藏布喜马拉雅特提斯造山带从裂谷—被动大陆边缘—前陆盆地的沉积盆地演化史。随着以雅鲁藏布带为代表的喜马拉雅特提斯打开,三叠纪到早侏罗世为特提斯早期裂开的大陆边缘裂谷盆地。早期裂谷中心部位不是现在大陆缝合线的雅鲁藏布一带,而在低分水岭带。晚侏罗世到早白垩世,雅鲁藏布江南测为典型被动大陆边缘,其沉积盆地沉降、海平面变化与沉积作用相吻合。晚白垩世到第三纪为前陆盆地演化阶段,从沉积作用可以识别出晚白垩世晚期为造山第一暮,第三纪初为第二幕。  相似文献   

An experiment on reservoir representation schemes to improve hydrologic prediction: coupling the national water model with the HEC-ResSim     

Jungho Kim  Laura Read  Lynn E. Johnson  David Gochis  Rob Cifelli  Heechan Han 《水文科学杂志》2020,65(10):1652-1666

ABSTRACT

This study experiments with reservoir representation schemes to improve the ability to model active water management in the National Water Model (NWM). For this purpose, we developed an integrated water management model, NWM-ResSim, by coupling the NWM with HEC-ResSim, and two reservoir representation schemes are tested: simulation of reservoir operations and retrieval of scheduled operations. The experiments focus on a pilot reservoir domain in the Russian River basin – Lake Mendocino, California – and its contributing watershed. The evaluation results suggest that the NWM-ResSim improves the simulation performance of reservoir outflow from this managed reservoir over the NWM default level pool routing scheme. The degree of this improvement depends on the suitability of the operation guidance; the reservoir operations simulation scheme could have acceptable errors for the purposes of water resources management, but not for flood operations. Results of the retrieval scheme of scheduled operations demonstrated better performance for sub-daily flood operations.  相似文献   

Variation of the gradient and balmer discontinuity during the eclipse of the variable RW Tauri: Comparison between observations and theory     

Pier Luigi Battistini  Massimo Fracassini  Laura E. Pasinetti 《Astrophysics and Space Science》1971,14(2):438-445

For the first time after Barbier and Chalonge's (1938, 1941) pioneering works, the variations of b andD during the eclipse of a variable (RT Tau), have been observed. The observations have been performed at the Observatories of Jungfraujoch and Haute Provence with the photoelectric system in seven colors of Geneva (Golay, 1964; Hauck, 1968). The comparison between the observed curves ofD and the theoretical ones, provides the limb darkening coefficients; the same comparison between the observed b (reddened) and theoretical ones (not reddened) together with that ofD, points out some anomalies of the variable RW Tau.

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Sommario Per la prima volta, dopo i primi lavori di Barbier e Chalonge (1938, 1941), sono state osservate le variazioni di b eD durante l'eclisse di una variabile (RW Tau). Le osservazioni sono state fatte agli Osservatori della Jungfraujoch e di Haute Provence col sistema fotoelettrico in sette colori di Ginevra (Golay, 1964; Hauck, 1968). Il confronto fra le curve osservate e teoriche diD, fornisce i coefficienti di oscuramento al bordo; lo stesso confronto fra i b osservati (arrossati) e quelli teorici (non arrossati) unitamente a quello delleD mette in evidenza alcune anomalie della variabile RW Tau.

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Effects of common reed (<Emphasis Type="Italic">Phragmites australis</Emphasis>) expansions on nitrogen dynamics of tidal marshes of the northeastern U.S.     

Lisamarie?WindhamEmail author  Laura?A.?Meyerson 《Estuaries and Coasts》2003,26(2):452-464

Several recent studies indicate that the replacement of extant species withPhragmites australis can alter the size of nitrogen (N) pools and fluxes within tidal marshes. Some common effects ofP. australis expansion are increased standing stocks of N, greater differentiation of N concentrations between plant tissues (high N leaves and low N stems), and slower whole-plant decay rates than competing species (e.g.,Spartina, Typha spp.). Some of the greater differences between marsh types involveP. australis effects on extractable and porewater pools of dissolved inorganic nitrogen (DIN) and N mineralization rates. Brackish and salt marshes show higher concentrations of DIN in porewater beneathSpartina spp. relative toP. australis, but this is not observed in freshwater tidal marshes whenP. australis is compared withTypha spp. or mixed plant assemblages. With few studies of concurrent N fluxes, the net effect ofP. australis on marsh N budgets is difficult to quantify for single sites and even more so between sites. The magnitude and direction of impacts ofP. australis on N cycles appears to be system-specific, driven more by the system and species being invaded than byP. australis itself. WhereP. australis is found to affect N pools and fluxes, we suggest these alterations result from increased biomass (both aboveground and belowground) and increased allocation of that biomass to recalcitrant stems. Because N pools are commonly greater inP. australis than in most other communities (due to plant and litter uptake), one of the most critical questions remaining is “From where is the extra N inP. australis communities coming?” It is important to determine if the source of the new N is imported (e.g., anthropogenic) or internallyproduced (e.g., fixed, remineralized organic matter). In order to estimate net impacts ofP. australis on marsh N budgets, we suggest that further research be focused on the N source that supports high standing stocks of N inP. australis biomass (external input versus internal cycling) and the relative rates of N loss from different marshes (burial versus subsurface flow versus denitrification).  相似文献   

Size Fractionation (Dissolved, Colloidal and Particulate) of Trace Metals in the Thur River, Switzerland     

Laura Sigg  Hanbin Xue  David Kistler  René Sshönenberger 《Aquatic Geochemistry》2000,6(4):413-434

The distribution of some trace metals (Cu, Zn, Ni, Co,Fe, Mn) and of DOC over a particulate (> 1 m),a colloidal (size < 0.45 m and molecular weight > 10 kD) and an ultrafiltered fraction (< 10 kD)was determined at several sites on the Thur River,Switzerland, at various times of the year. Thecomplexation of Cu by strong ligands in theultrafiltrate and in the conventional filtrate (<0.45 m) was compared using a ligand-exchange/CSV method.The <0.45 m concentrations of Cu (from anaverage of 7 nM to 24 nM), Zn (<5–23 nM), Ni (5–13 nM),Co (1.5–3 nM) and Mn (7–92 nM)increased downstream. The major part of Cu, Zn, Niand Co usually occurred in the ultrafiltratefraction at all sites, whereas Fe and Mn were mostlyin the particulate fraction, under conditions of lowsuspended matter content (< 10 mg L^-1) in theriver. The percentage of metal in the colloidalfraction, with respect to the 0.45-m filtrate,decreased in the order: Cu (median 11%) > Zn Ni(median 5–6%) > Mn Co (median < 5%). DOCalso consisted mostly of molecules in the < 10 kDrange.Cu was strongly complexed by natural organic ligandsin all filtrate and ultrafiltrate samples. A largepart of the strong Cu binding ligands consisted ofcompounds in the < 10 kD range, but colloidalligands with similar properties also occurred. Cu wasdistributed among the dissolved and the colloidalligands, roughly in proportion to organic carbon.The colloidal fraction (as defined here) did notincrease in its proportional amount downstream and wasonly of limited significance in transporting traceelements in the Thur River under low discharge conditions.  相似文献