The CO₂ absorption method as an alternative to benzene synthesis method forC dating     

Riffat M. Qureshi  Ramon Aravena  Peter Fritz  Robert Drimmie 《Applied Geochemistry》1989,4(6)

A fast and economical routine sample preparation system is described for direct counting of¹⁴C for hydrological purposes. The method employs commercially available CO₂ absorbers, such as Carbosorb, and liquid scintillation counters. The maximum error involved individual analyses is about ±4pmc (1 δ) on the Beckman counter and about ±2 pmc on the Quantulus counter with a resulting detection limit of 21,000–29,000 a for the Beckman LS7500 and 1220 Quantulus, respectively for a counting time of 1000 min. To avoid physical weighing procedures, an indirect method is presented to determine the grams of C absorbed in the counting solution by using the H-# quench monitor technique available in the Beckman liquid scintillation counters. On one sample preparation system at least five samples can be prepared per normal working day. The applicability of the CO₂-absorption method is discussed with reference to two field sites and with reference to comparisons with data obtained on the same samples measured with conventional techniques.  相似文献   

From granitoid to kyanite-bearing micaschist during fluid-assisted shearing (Ile d’Yeu, France)     

Caroline Sassier  Philippe Boulvais  Denis Gapais  Ramon Capdevila  Hervé Diot 《International Journal of Earth Sciences》2006,95(1):2-18

We describe amphibolite-facies shear zones affecting an orthogneiss from the Armorican Hercynian belt (Ile d’Yeu, western France). The deformation pattern is consistent with top-to-the-South thrusting followed by E–W extension, as documented elsewhere in the region. Shearing was accompanied by channelled fluid flow that transformed the orthogneiss into a peraluminous micaschist. Structural and mineralogical data indicate rather early strain localization. Then, temperature increase associated with crustal thickening favoured more distributed deformations marked by shear zone stretching and the development of a HT regional foliation. Chemical analyses made across five shear zones show mass transfers that mainly implied losses in Ca and Na, and gains in H₂O, Mg, and K. Most results indicate constant volume transformation, but some suggest records of either gains or losses of volume (between +20% and −30%). This might reflect variable records of fluid-rock interactions according to the timing of initiation and subsequent evolution of individual shear zones, early thrusting stages being marked by up-temperature flow, and late thrusting stages by down-temperature flow. δ¹⁸O analyses suggest that fluids experienced significant isotopic exchange with orthogneisses.  相似文献   

The characterization of sardine (Sardina pilchardus Walbaum) schools off the Spanish-Atlantic coast   总被引：1，自引：0，他引：1  

Muino  Ramon; Carrera  Pablo; Iglesias  Magdalena 《ICES Journal of Marine Science》2003,60(6):1361-1372

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Suspended sediment transport in a small Mediterranean agricultural catchment     

Joan Estrany  Celso Garcia  Ramon J. Batalla 《地球表面变化过程与地形》2009,34(7):929-940

The aim of this study is to analyze suspended sediment transport in a Mediterranean agricultural catchment under traditional soil and water conservation practices. Field measurements were conducted in Can Revull, a small ephemeral catchment (1.03 km²) on the island of Mallorca. This study uses continuous turbidity records to analyse suspended sediment transport regimes, construct and interpret multiple regression models of total suspended sediment concentration (SSC) and of SSC related to stormflow discharge, and assess the sediment loads and yields of three hydrological years (2004–2005 to 2006–2007). An annual average SSC of 17.3 mg l^?1, with a maximum of 2270 mg l^?1, was recorded in the middle of the winter period when rainfall intensities are high and headwater slopes are ploughed and thus bare. Strong seasonal contrasts of baseflow dynamics associated with different degrees of dilution provide a large scatter in SSC and in the derived rating curves, reflecting that other factors control the supply of suspended sediment. Multiple regression models identify rainfall intensity as the most significant variable in sediment supply. However, under baseflow conditions, physical and biological processes generate sediment in the channel that is subsequently removed during high flow. In contrast, when baseflow is not present, rainfall intensity is the only process that supplies sediment to the channel, mostly from hillslopes. Considering the study period as average in terms of total annual rainfall and intensities, suspended sediment yields were an order of magnitude lower than those obtained in other Mediterranean catchments, a factor that can be related to the historical use of soil conservation practices. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Factors determining subsidence in urbanized floodplains: evidence from MT‐InSAR in Seville (southern Spain)          下载免费PDF全文

Ana Ruiz‐Constán  Antonio M. Ruiz‐Armenteros  Jesús Galindo‐Zaldívar  Francisco Lamas‐Fernández  Joaquim João Sousa  Carlos Sanz de Galdeano  Antonio Pedrera  Sergio Martos‐Rosillo  Miguel Caro Cuenca  J. Manuel Delgado  Ramon F. Hanssen  Antonio J. Gil 《地球表面变化过程与地形》2017,42(14):2484-2497

Major rivers have traditionally been linked with important human settlements throughout history. The growth of cities over recent river deposits makes necessary the use of multidisciplinary approaches to characterize the evolution of drainage networks in urbanized areas. Since under‐consolidated fluvial sediments are especially sensitive to compaction, their spatial distribution, thickness, and mechanical behavior must be studied. Here, we report on subsidence in the city of Seville (Southern Spain) between 2003 and 2010, through the analysis of the results obtained with the Multi‐Temporal InSAR (MT‐InSAR) technique. In addition, the temporal evolution of the subsidence is correlated with the rainfall, the river water column and the piezometric level. Finally, we characterize the geotechnical parameters of the fluvial sediments and calculate the theoretical settlement in the most representative sectors. Deformation maps clearly indicate that the spatial extent of subsidence is controlled by the distribution of under‐consolidated fine‐grained fluvial sediments at heights comprised in the range of river level variation. This is clearly evident at the western margin of the river and the surroundings of its tributaries, and differs from rainfall results as consequence of the anthropic regulation of the river. On the other hand, this influence is not detected at the eastern margin due to the shallow presence of coarse‐grain consolidated sediments of different terrace levels. The derived results prove valuable for implementing urban planning strategies, and the InSAR technique can therefore be considered as a complementary tool to help unravel the subsidence tendency of cities located over under‐consolidated fluvial deposits. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Easily altered minerals and reequilibrated fluid inclusions provide extensive records of fluid and thermal history: gypsum pseudomorphs of the Tera Group, Tithonian-Berriasian, Cameros Basin     

Laura González-Acebrón  Robert H. Goldstein  Ramon Mas  Jose Arribas 《Central European Journal of Geosciences》2012,4(2):246-260

This study reports a complex fluid and thermal history using petrography, electron microprobe, isotopic analysis and fluid inclusions in replacement minerals within gypsum pseudomorphs in Tithonian-Berriasian lacustrine deposits in Northern Spain. Limestones and dolostones, formed in the alkaline lakes, contain lenticularly shaped gypsum pseudomorphs, considered to form in an evaporative lake. The gypsum was replaced by quartz and non-ferroan calcite (Ca-2), which partially replaces the quartz. Quartz contains solid inclusions of a preexisting non-ferroan calcite (Ca-1), anhydrite and celestine. High homogenization temperatures (T _h ) values and inconsistent thermometric behaviour within secondary fluid inclusion assemblages in quartz (147?C351°C) and calcite (108?C352°C) indicate high temperatures after precipitation and entrapment of lower temperature FIAs. Th are in the same range as other reequilibrated fluid inclusions from quartz veins in the same area that are related to Cretaceous hydrothermalism. Gypsum was replaced by anhydrite, likely during early burial. Later, anhydrite was partially replaced by Ca-1 associated with intermediate burial temperatures. Afterward, both anhydrite and Ca-1 were partially replaced by quartz and this by Ca-2. All were affected during higher temperature hydrothermalism and a CO₂-H₂O fluid. Progressive heating and hydrothermal pulses, involving a CO₂-H₂O fluid, produce the reequilibration of the FIAs, which was followed by uplift and cooling.  相似文献   

Large floods,alluvial overprint,and bedrock erosion     

Jens M. Turowski  Alexandre Badoux  James Leuzinger  Ramon Hegglin 《地球表面变化过程与地形》2013,38(9):947-958

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Reach and catchment-scale influences on invertebrate assemblages in a river with naturally high fine sediment loads     

Cristina Buendia  Chris N. Gibbins  Damià Vericat  Ramon J. Batalla 《Limnologica》2013,43(5):362-370

Stream invertebrate distribution patterns reflect local sedimentary and hydraulic conditions, which in turn are influenced by a range of factors operating at larger scales. We assessed whether spatial variation in invertebrate assemblages across a meso-scale catchment is best understood in terms of the characteristics of the study reaches themselves or the characteristics of respective upstream catchment areas. The study river experiences naturally high fine sediment loads as a result of the extraordinary supply of sediment from high erodible marls in its catchment. We hypothesized that between-reach variation in the volume of fine sediment stored within the channel results from a combination of reach and upstream catchment characteristics, and that these characteristics help explain variation in invertebrate assemblages. The storage of fine sediment in study reaches correlated with a number of upstream catchment characteristics, as well as reach-scale hydraulic conditions. Variability in invertebrate assemblages correlated most strongly (62% of variance explained) with the characteristics of the catchment upstream from each reach (area of contribution), with the characteristics of the reaches accounting for only 35% of the variability. The explanatory power of the reach-scale habitat variables was reduced when the effect of upstream catchment conditions was removed. This suggests inbuilt effects of larger scale conditions on reach habitat and invertebrate assemblages. Results lend support to theories of scale hierarchy within river systems and help emphasize the need to target management at upstream catchment areas.  相似文献   

Modelling the Effect of Tree Foliage on Sprayer Airflow in Orchards   总被引：1，自引：0，他引：1  

Ayenew Melese Endalew  Christof Debaer  Nick Rutten  Jef Vercammen  Mulugeta Admasu Delele  Herman Ramon  Bart M. Nicolaï  Pieter Verboven 《Boundary-Layer Meteorology》2011,138(1):139-162

The effect of tree foliage on sprayer airflow through pear trees in a fruit orchard was studied and modelled in detail. A new three-dimensional (3-D) computational fluid dynamics model that integrates the 3-D canopy architecture with a local closure model to simulate the effect of the stem and branches and leaves of trees separately on airflow was developed. The model was validated with field observations made in an experimental orchard (pcfruit, Sint-Truiden, Belgium) in spring and summer 2008 and was used to investigate the airflow from three air-assisted orchard sprayers (Condor V, Duoprop and AirJet quatt). Velocity magnitudes were measured before and behind leafless and fully-leafed pear canopies across the row while the operating sprayers are passing along the row, and were compared with the simulations. The simulation results predicted the measured values well with all the local relative errors within 20%. The effect of foliar density on airflow from the three air assisted sprayers was manifested by changing the magnitude and direction of the sprayers’ air velocity behind the canopy, especially at the denser regions of the canopy and by changing the pattern of velocity decay horizontally along the jet. The developed methodology will also allow a thorough investigation of atmospheric airflow in canopy structures.  相似文献   

Interaction between deep and shallow groundwater systems in areas affected by Quaternary tectonics (Central Italy): a geochemical and isotope approach   总被引：4，自引：3，他引：1  

Marco Petitta  Paolo Primavera  Paola Tuccimei  Ramon Aravena 《Environmental Earth Sciences》2011,63(1):11-30

Hydro- and isotope geochemistry are used to refine groundwater conceptual models in two areas of central Italy (Acque Albule Basin and Velino River Valley) affected by extensional Quaternary tectonics, where deep and shallow groundwater flow systems are interacting. The role of geology, of recent deposits filling the plains and of main tectonic features controlling groundwater flowpaths and deep-seated fluids emergences are investigated and discussed. Environmental isotopes (²H and ¹⁸O) confirm recharge in the surrounding carbonate aquifers, and meteoric origin of both shallow and deep groundwater. Major ion chemistry indicates a mixing between shallow Ca-HCO₃ groundwater from carbonate aquifers and deep Ca-HCO₃-SO₄ groundwater, characterised by higher salinity and temperature and high concentration in sulphates. Isotopic composition of dissolved sulphates (δ ³⁴S and δ ¹⁸O) and dissolved inorganic carbon (δ ¹³C), henceforth indicated as DIC, are used to verify the presence of different sources of groundwater, and to validate the mixing model suggested by the major ion analyses. Sulphate isotope composition suggests a marine origin for the groundwater characterised by elevated sulphate concentration, whose source is present in the deep buried sequences. Carbon isotope composition confirms the role of a DIC source associated to CO₂ degassing of a deep reservoir. Groundwater conceptual models are improved underlining the importance of Plio-Pleistocene sequences filling the tectonic depression. In the Acque Albule area, the travertine plateau represents a mixing stratified aquifer, where deep groundwater contribution is spread into the shallow aquifer. The alluvial–clastic–lacustrine leaky aquifer of Velino Valley enables a complete mixing of shallow and deep groundwater allowing spot-located discharge of deep groundwater along tectonic patterns and facilitating sulphate reduction in the lacustrine sediments, explaining locally the presence of H₂S.  相似文献