Hydrochemistry and environmental isotopes of spring water and their relation to structure and lithology identified with remote sensing methods in Wadi Araba,Egypt     

Wannous  Manal  Theilen-Willige  Barbara  Troeger  Uwe  Falk  Marianne  Siebert  Christian  Bauer  Florian 《Hydrogeology Journal》2021,29(6):2245-2266

Springs located at the historical sites of Wadi Araba (Eastern Desert of Egypt) and emerging from the escarpments of the Northern and Southern Galala Plateaus were investigated. A combination of methods, including hydrochemistry, stable and radioisotope composition, and structural analyses based on satellite data, provided information about the structure of the subsurface and the derived groundwater flow paths. Satellite images reveal karst features within the northern plateau, e.g. conical landforms. Karstic caves were documented along both escarpments. Chemical analysis of floodwater from Wadi Araba indicates higher concentrations of terrestrial salts compared to floodwaters from central and southern parts of the desert. δ¹⁸O and δ²H signatures in spring waters resemble those of floodwater and fall on the global meteoric water line, confirming their fast infiltration with minor influence of evaporation. The aquifer feeding the springs of the Northern Galala Plateau has low retention and the springs dry out quickly, even after heavy rainfall. Contrastingly, ³H activities in springs emerging from the Southern Galala Plateau refer to much slower subsurface passage. With respect to ³H content (3.8 TU) in recent flood waters, the spring water at Southern Galala Plateau contains about 40% recently recharged groundwater. However, its largest spring—the St. Antony spring—discharges water with a radiocarbon age of about 15,000 years. In combination with this spring’s constant and high discharge over a period of several months, that age estimate suggests a large reservoir with moderate to high retention.

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Sediment dynamics in an upland temperate catchment: changing sediment sources,rates and deposition     

Robert G. Hatfield  Barbara A. Maher  Jacqueline M. Pates  Philip A. Barker 《Journal of Paleolimnology》2008,40(4):1143-1158

We examine sediment dynamics in an upland, temperate lake system, Lake Bassenthwaite (NW England), in the context of changing climate and land use, using magnetic and physical core properties. Dating and analysis of the sedimentary records of nine recovered cores identify spatially variable sedimentation rates across the deep lake basin. Mineral magnetic techniques, supported by independent geochemical analyses, identify significant variations both in sediment source and flux over the last ∼2100 years. Between ∼100 years BC and ∼1700 AD, sediment fluxes to the lake were low and dominated by material sourced from within the River Derwent sub-catchment (providing 80% of the hydraulic load at the present day). Post-1700 AD, the lake sediments became dominantly sourced from Newlands Beck (presently providing ∼10% of the lake’s hydraulic load). Three successive, major pulses of erosion and increased sediment flux appear linked to specific activities within the catchment, specifically: mining activities and associated deforestation in the mid-late nineteenth century; agricultural intensification in the mid-twentieth century and, within the last decade, the additional possible impact of climate change. These results are important for all upland areas as modifications in climate become progressively superimposed upon the effects of previous and/or ongoing anthropogenic catchment disturbance.  相似文献   

Authigenic replacement of cyanobacterially precipitated calcium carbonate by aluminium‐silicates in giant microbialites of Lake Van (Turkey)     

Barbara Kremer  Jzef Ka mierczak  Stephan Kempe 《Sedimentology》2019,66(1):285-304

Studies of modern cyanobacterial mats and biofilms show that they can precipitate minerals as a consequence of metabolic and degradational activities paired with ambient hydrochemical conditions. This study looked at modern microbial mats forming giant, tower‐like, groundwater‐fed, calcareous microbialites in the world's largest, highly alkaline lake; Van Gölü (Lake Van), East Turkey. Results show that microbial systems play a role not only in carbonate precipitation but also in the formation of siliceous mineral phases. Transmitted light microscopy, scanning electron microscopy and spectral observations revealed that, within the extracellular polymeric substances excreted by the mats abundant minute aragonite grains precipitated first in vivo. These minute grains were quickly succeeded and/or supplemented in the dead biomass of the cyanobacterial mat by authigenic Al–Mg–Fe siliceous phases. Silicon dioxide is available in large concentrations in the highly alkaline water of Lake Van. Divalent cations (Ca and Mg) are delivered to the microbialites mostly by groundwater springs. The precipitation of the fine‐grained siliceous phases is probably mediated by bacteria degrading the cyanobacterial biomass and complexing the excessive cations with their extracellular polymeric envelopes. The bacteria serve as nucleation centres for the subsequent precipitation of siliceous mineral phases. Generally, the biphasic (calcareous and siliceous) mineralization – characterizing Lake Van microbialites – is controlled by their interior highly dynamic hydrogeochemical situation. There, the dramatically different alkaline lake water and the Ca–Mg‐charged groundwater mix at various rates. The early diagenetic replacement of the in vivo aragonite by authigenic siliceous phases significantly increases the fossilization potential of the mat‐forming cyanobacteria. Lake Van and its giant microbialite tufa towers act as a model explaining the transformation of early diagenetic mineral phases observed in many modern and ancient carbonate marine deposits, particularly those influenced by diffusion of silica‐enriched and metal‐enriched pore waters from below the water–sediment interface.  相似文献   

Development of a Practical Tool for the Assessment of Biological Performances in Wastewater Treatment Plants          下载免费PDF全文

Francesca F. Malinverni  Barbara Ruffino 《洁净——土壤、空气、水》2016,44(11):1435-1443

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Assessment of the Global and Regional Land Hydrosphere and Its Impact on the Balance of the Geophysical Excitation Function of Polar Motion   总被引：2，自引：0，他引：2  

Małgorzata Wińska  Jolanta Nastula  Barbara Kołaczek 《Acta Geophysica》2016,64(1):270-292

The impact of continental hydrological loading from land water, snow and ice on polar motion excitation, calculated as hydrological angular momentum (HAM), is difficult to estimate, and not as much is known about it as about atmospheric angular momentum (AAM) and oceanic angular momentum (OAM). In this paper, regional hydrological excitations to polar motion are investigated using monthly terrestrial water storage data derived from the Gravity Recovery and Climate Experiment (GRACE) mission and from the five models of land hydrology. The results show that the areas where the variance shows large variability are similar for the different models of land hydrology and for the GRACE data. Areas which have a small amplitude on the maps make an important contribution to the global hydrological excitation function of polar motion. The comparison of geodetic residuals and global hydrological excitation functions of polar motion shows that none of the hydrological excitation has enough energy to significantly improve the agreement between the observed geodetic excitation and geophysical ones.  相似文献   

Crude Oil Metabolites in Groundwater at Two Spill Sites          下载免费PDF全文

Barbara A. Bekins  Isabelle M. Cozzarelli  Melinda L. Erickson  Ross A. Steenson  Kevin A. Thorn 《Ground water》2016,54(5):681-691

Two groundwater plumes in north central Minnesota with residual crude oil sources have 20 to 50 mg/L of nonvolatile dissolved organic carbon (NVDOC). These values are over 10 times higher than benzene and two to three times higher than Diesel Range Organics in the same wells. On the basis of previous work, most of the NVDOC consists of partial transformation products from the crude oil. Monitoring data from 1988 to 2015 at one of the sites located near Bemidji, MN show that the plume of metabolites is expanding toward a lakeshore located 335 m from the source zone. Other mass balance studies of the site have demonstrated that the plume expansion is driven by the combined effect of continued presence of the residual crude oil source and depletion of the electron accepting capacity of solid phase iron oxide and hydroxides on the aquifer sediments. These plumes of metabolites are not covered by regulatory monitoring and reporting requirements in Minnesota and other states. Yet, a review of toxicology studies indicates that polar metabolites of crude oil may pose a risk to aquatic and mammalian species. Together the results suggest that at sites where residual sources are present, monitoring of NVDOC may be warranted to evaluate the fates of plumes of hydrocarbon transformation products.  相似文献   

Central Asian aridification during the late Eocene to early Miocene inferred from preliminary study of shallow marine-eolian sedimentary rocks from northeastern Tajik Basin     

Xin Wang  Brian Kraatz  Jin Meng  Barbara Carrapa  Peter Decelles  Mark Clementz  Sherzod Abdulov  FaHu Chen 《中国科学:地球科学(英文版)》2016,59(6):1242-1257

The tempo-spatial development of the Cenozoic Asian aridification across the Eocene-Oligocene and its controlling factors are important scientific topics in Earth Sciences, which are pertinent to regional and global tectonic and climatic events. However, sedimentary rocks preserving the record of aridification during this time from central Asia (ACA) are rare. Here we present a preliminary analysis of sedimentary facies of the lower Paleogene in the northeastern Tajik Basin, which reveals that: the lower part of the studied section is dominated by shallow marine deposits of the Paratethys, the middle part is typical of alternations of eolian dune and fluvial deposits, the upper part is represented by eolian loess-sandy loess (L&SL) like facies, and the top exhibits alternations of fluvial-lacustrine and loess like facies. Based on a chronological framework derived from preliminary magnetostratigraphy, published U-Pb dating of a volcanic ash, and regional litho-stratigraphic correlations, we determine that eolian and L&SL facies accumulated in the northeastern Tajik Basin during the Late Eocene and through most of the Oligocene. These sedimentary units indicate that semi-arid to arid environments of ACA had developed at least since the late Eocene. This initial aridification is closely linked to the westward retreat of the Paratethys that was likely driven by a combination of tectonic activity and sea level changes.  相似文献   

Predicting torsion‐induced lateral displacements for pushover analysis: Influence of torsional system characteristics     

Mario De Stefano  Barbara Pintucchi 《地震工程与结构动力学》2010,39(12):1369-1394

The increasing popularity of simplified nonlinear methods in seismic design has recently led to many proposals for procedures aimed at extending pushover analysis to plan asymmetric structures. In terms of practical applications, one particularly promising approach is based on combining pushover analysis of a 3D structural model with the results of linear (modal) dynamic analysis. The effectiveness of such procedure, however, is contingent on one fundamental requirement: the elastic prediction of the envelope of lateral displacements must be conservative with respect to the actual inelastic one. This paper aims at verifying the above assumption through an extensive parametric analysis conducted with simplified single‐storey models. The main structural parameters influencing torsional response in the elastic and inelastic range of behaviour are varied, while devoting special attention to the system stiffness eccentricity and radius. The analysis clarifies the main features of inelastic torsional response of different types of building structures; in this manner, it is found that the above‐mentioned method is generally suitable for structures characterized by moderate to large torsional stiffness, whereas it cannot be recommended for extremely torsionally stiff structures, as their inelastic torsional response almost always exceeds the elastic one. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Legal challenges to the management of transboundary watercourses in Central Asia under the conditions of Eurasian Economic Integration     

Daria S. Boklan  Barbara Janusz-Pawletta 《Environmental Earth Sciences》2017,76(12):437

Worldwide experience has shown that interstate economic integration can help states in strengthening of management of transboundary waters and international water law serves as a reference for developing of relevant interstate cooperation. Transboundary waters in Central Asia play important role in the economic cooperation among riparian states, including those who are members of the Eurasian Economic Union (EAEU). At the current stage of transboundary waters management in Central Asia, the obsolete legal status is evident. The international water law sources developed under the United Nations’ auspices have no binding application due to luck of formal membership of the EAEU states in these treaties. Also the regional set of regulations, especially for the Aral Sea Basin, needs further enhancement and more efficient implementation. The bilateral interstate regulatory framework of the managemennt of waters shared by EAEU states in Central Asia requires development of additional rules to enable better accommodation of challenges existing in terms of the current interstate cooperation. Having said that can one further assume that EAEU could serve as a new legal framework for more effective cooperation on transboundary watercourses in Central Asia? The answer might be yes, but… the current stage of the legal framework for cooperation on transboundary waters within the EAEU requires sufficient enhancements in terms of developing its legal and institutional framework. The first condition for EAEU to serve as framework for cooperation on transboundary waters of Central Asia is to strengthen the regulatory framework for the cooperation of EAEU member states regarding environmental issues in general and transboundary water relations in particular, able to accommodate two main goals: environmental protection on the one hand and economic development on the other hand. The EAEU legal framework shall also lead to improvement of existing institutional cooperation and a dispute settlement mechanism on transboundary waters shared by the member states of the EAEU.  相似文献   

Using nitrate to quantify quick flow in a karst aquifer   总被引：3，自引：0，他引：3  

Mahler BJ  Garner BD 《Ground water》2009,47(3):350-360

In karst aquifers, contaminated recharge can degrade spring water quality, but quantifying the rapid recharge (quick flow) component of spring flow is challenging because of its temporal variability. Here, we investigate the use of nitrate in a two-endmember mixing model to quantify quick flow in Barton Springs, Austin, Texas. Historical nitrate data from recharging creeks and Barton Springs were evaluated to determine a representative nitrate concentration for the aquifer water endmember (1.5 mg/L) and the quick flow endmember (0.17 mg/L for nonstormflow conditions and 0.25 mg/L for stormflow conditions). Under nonstormflow conditions for 1990 to 2005, model results indicated that quick flow contributed from 0% to 55% of spring flow. The nitrate-based two-endmember model was applied to the response of Barton Springs to a storm and results compared to those produced using the same model with δ¹⁸O and specific conductance (SC) as tracers. Additionally, the mixing model was modified to allow endmember quick flow values to vary over time. Of the three tracers, nitrate appears to be the most advantageous because it is conservative and because the difference between the concentrations in the two endmembers is large relative to their variance. The δ¹⁸O-based model was very sensitive to variability within the quick flow endmember, and SC was not conservative over the timescale of the storm response. We conclude that a nitrate-based two-endmember mixing model might provide a useful approach for quantifying the temporally variable quick flow component of spring flow in some karst systems.  相似文献