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   

400 Years of Astronomical Telescopes     

Peter von Ballmoos  Bernhard Brandl  Ramon Khanna 《Experimental Astronomy》2009,25(1-3):1-2

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The evolution of a tropical rainforest/grassland mosaic in southeastern Brazil since 28,000 C yr BP based on carbon isotopes and pollen records     

Luiz Carlos Ruiz Pessenda  Paulo Eduardo De Oliveira  Milene Mofatto  Vanda Brito de Medeiros  Ricardo Jos Francischetti Garcia  Ramon Aravena  Jos Albertino Bendassoli  Accio Zuniga Leite  Antonio Roberto Saad  Mario Lincoln Etchebehere 《Quaternary Research》2009,71(3):437-452

The lack of paleoecological records from the montane Atlantic Rainforest of coastal Brazil, a hotspot of biological diversity, has been a major obstacle to our understanding of the vegetational changes since the last glacial cycle. We present carbon isotope and pollen records to assess the impact of the glaciation on the native vegetation of the Serra do Mar rainforest in São Paulo, Brazil. From ca. 28,000 to  22,000 ¹⁴C yr BP, a subtropical forest with conifer trees is indicative of cool and humid conditions. In agreement carbon isotopic data on soil organic matter suggest the presence of C₃ plants and perhaps C₄ plants from  28,000 to  19,000 ¹⁴C yr BP. The significant increase in the sedimentation rate and algal spores from  19,450 to  19,000 ¹⁴C yr BP indicates increasing humidity, associated to an erosion process between  19,000 and  15,600 ¹⁴C yr BP. From  15,600 ¹⁴C yr BP to present there is a substantial increase in arboreal elements and herbs, indicating more humid and warmer climate. From  19,000 to  1000 ¹⁴C yr BP, δ¹³C values indicated the predominance of C₃ plants. These results are in agreement with studies in speleothems of caves, which suggest humid conditions during the last glacial maximum.  相似文献   

Quantitative observations of a major coral bleaching event in Barbados, Southeastern Caribbean     

Hazel A. Oxenford  Ramon Roach  Angelique Brathwaite  Leonard Nurse  Renata Goodridge  Fabian Hinds  Kim Baldwin  Christine Finney 《Climatic change》2008,87(3-4):435-449

In late summer 2005 a mass coral bleaching event occurred in the Caribbean. Here we quantify coral bleaching in Barbados at six sites on the island’s sheltered west and exposed southwest coasts, including nearshore fringing and patch reefs and offshore bank reef habitats. Onset of coral bleaching occurred in late August 2005 and persisted for many months after temperatures cooled. All reef habitats and virtually all coral taxa were affected, with an average of 70.6% of all colonies bleaching. Nearshore reefs (<10 m depth) were affected more severely than offshore deeper reefs (>15 m) with an average of 80.6% of all coral colonies bleaching compared with 60.5% on the latter. Inter-species variation in susceptibility to bleaching was marked with >90% of colonies bleaching in some species whilst <10% bleached in others. Follow-up surveys revealed low coral mortality, with an overall mean of 3.8% partial colony death across all species and reefs by February 2006. However, bleached condition has persisted with a mean of 37.7% of all coral colonies still bleached after 5 1/2 months, indicating that loss of live coral is likely to continue for some time. This event represents the most severe bleaching episode ever witnessed on Barbados’ reefs and emphasises the vulnerability of small island states, with a high reliance on healthy coral reef ecosystem services, to elevated sea water temperatures associated with climate variability and global climate change.  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