Anomalous content of chromium in a Cretaceous sandstone aquifer of the Bauru Basin,state of São Paulo,Brazil     

Reginaldo Bertolo  Christine Bourotte  Leonardo Marcolan  Sonia Oliveira  Ricardo Hirata 《Journal of South American Earth Sciences》2011,31(1):69-80

Anomalous and natural concentrations of Cr⁶⁺, occasionally exceeding the permitted limit for human consumption (0.05 mg/L), have been detected in groundwater in the northwestern region of the state of São Paulo. As part of a water-rock interaction investigation, this article describes the chemical and mineralogical characterization of rock samples taken from boreholes in the municipality of Urânia, with the objective of identifying Cr-bearing minerals and determining how chromium is associated with these minerals. Rock sample analysis were performed using X-ray Fluorescence, X-ray Diffraction, Scanning Electron Microscopy, electron microprobe and sequential extraction techniques. Chemical analyses indicated that the quartzose sandstones show a geochemical anomaly of chromium, with an average content of 221 ppm, which is higher than the reported chromium content of generic sandstones (35 ppm). Diopside was identified as the primary Cr-bearing mineral potentially subject to weathering processes, with a chromium content of up to 1.2% as Cr₂O₃. Many of the diopside grains showed dissolution features, confirming the occurrence of weathering. Sequential extraction experiments indicated that 99.3% of the chromium in samples is tightly bonded to minerals, whereas 0.24% is weakly bonded via adsorption. Assuming hypothetically that all adsorbed chromium is released via desorption, the theoretical Cr concentration in water would be one order of magnitude higher than the concentrations of Cr⁶⁺ detected in groundwater.  相似文献   

A spatter-forming, large-scale paroxysm at Stromboli Volcano (Aeolian Islands, Italy): insight into magma evolution and eruption dynamics     

Sonia La Felice  Patrizia Landi 《Bulletin of Volcanology》2011,73(9):1393-1406

This study focuses on a pyroclastic sequence related to a large-scale paroxysm that occurred during the seventeenth century ad and which can be considered one of the most powerful and hazardous explosive events at the volcano in the past few centuries. Paroxysms are energetic, short-lived explosions which sporadically interrupt normal Strombolian activity at Stromboli and commonly erupt a deep-derived, volatile-rich crystal-poor high-potassium basalt (“low porphyricity” (LP)), together with a shallow, degassed crystal-rich high-potassium to shoshonitic basalt (“high porphyricity” (HP)), which feed normal activity at the volcano. The studied deposit, crops out along the flanks of Sciara del Fuoco and, from base to top, consists of: (1) a layer of HP and LP ash and lapilli; (2) an unwelded layer of coarse HP lapilli and flattened dark scoriae; (3) weakly welded spatter made up of dense HP pyroclasts at the base, overlain by strongly vesicular LP clasts. The textural and chemical zoning of minerals and the glass chemistry of the LP products record repeated mafic recharge events, mixing with an old mushy body and episodes of rapid crystallization due to sudden degassing. Collapse of a foam layer originated by deep degassing probably triggered this large-scale, spatter-forming paroxysm. Decompression induced rapid degassing and vesiculation of the deep volatile-rich magma. The rapid ascent of the foamy magma blob pushed the shallow HP magma out and finally produced a fire fountain that emplaced the LP portion of the spatter.  相似文献   

Using soil moisture forecasts for sub-seasonal summer temperature predictions in Europe     

René Orth  Sonia I. Seneviratne 《Climate Dynamics》2014,43(12):3403-3418

Soil moisture exhibits outstanding memory characteristics and plays a key role within the climate system. Especially through its impacts on the evapotranspiration of soils and plants, it may influence the land energy balance and therefore surface temperature. These attributes make soil moisture an important variable in the context of weather and climate forecasting. In this study we investigate the value of (initial) soil moisture information for sub-seasonal temperature forecasts. For this purpose we employ a simple water balance model to infer soil moisture from streamflow observations in 400 catchments across Europe. Running this model with forecasted atmospheric forcing, we derive soil moisture forecasts, which we then translate into temperature forecasts using simple linear relationships. The resulting temperature forecasts show skill beyond climatology up to 2 weeks in most of the considered catchments. Even if forecasting skills are rather small at longer lead times with significant skill only in some catchments at lead times of 3 and 4 weeks, this soil moisture-based approach shows local improvements compared to the monthly European Centre for Medium Range Weather Forecasting (ECMWF) temperature forecasts at these lead times. For both products (soil moisture-only forecast and ECMWF forecast), we find comparable or better forecast performance in the case of extreme events, especially at long lead times. Even though a product based on soil moisture information alone is not of practical relevance, our results indicate that soil moisture (memory) is a potentially valuable contributor to temperature forecast skill. Investigating the underlying soil moisture of the ECMWF forecasts we find good agreement with the simple model forecasts, especially at longer lead times. Analyzing the drivers of the temperature forecast skills we find that they are mainly controlled by the strengths of (1) the soil moisture-temperature coupling and (2) the soil moisture memory. We find a negative relationship between these controls that weakens the forecast skills, nevertheless there is a middle ground between both controls in several catchments, as shown by our results.  相似文献   

Benthic foraminifera and geochemical studies with influence on pollution studies along the coast of Cuddalore,Tamil Nadu-ITS,India     

M. Suresh Gandhi  A. Sonia Nathan 《Arabian Journal of Geosciences》2014,7(3):917-925

Foraminifers, being sensitive to minute changes, either undergo morphological changes or even disappear from the area completely due to pollution or under unfavourable conditions. The characteristics of foraminifers to incorporate the signature of presence of pollutants are considered to be an effective tool for temporal pollution monitoring studies. Totally, 12 offshore samples (both sediment and water) were taken along a normal profile along the coast of Cuddalore for pollution studies. Apart from foraminiferal studies, geochemical studies of the sediments collected are also undertaken to correlate and substantiate the findings. The near-shore area has a higher concentration of trace elements. If these concentrations exceed or go below permissible limits, it is collateral for the marine community and for those who consume these marine resources. The concentration of trace elements like lead, zinc, manganese, copper, chromium and nickel was illustrated to give an idea of the trace element concentration of the study area. The sedimentological studies reveal the organic matter and calcium carbonate content of the samples, and the bottom water measurements reveal the temperature, salinity and dissolved oxygen of sample locations. These are used to determine whether the conditions prevailing could sustain life. The ratio of living to dead species is also determined and correlated with sedimentological and geochemical parameters. Pollution studies have given way to identify morphological abnormalities in the species mainly in Spiroloculina, Quinqueloculina, Elphidium, etc. but we could not find many effects among the faunal assemblages because of the nature of the sediments found in that area.  相似文献   

Influence of the hyporheic zone on the phosphorus dynamics of a large gravel‐bed river,Garonne River,France     

Philippe Vervier  Sonia Bonvallet‐Garay  Sabine Sauvage  H. Maurice Valett  José‐Miguel Sanchez‐Perez 《水文研究》2009,23(12):1801-1812

Phosphorus (P) concentrations in sediments and in surface and interstitial water from three gravel bars in a large river (Garonne River, southern France) were measured daily, downstream of a wastewater treatment plant for a city of 740 000 inhabitants (Toulouse). Measurements were made of vertical hydraulic gradient (VHG), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP) and total phosphorus (TP) in water and of three extractable forms of phosphorus (water extractable, NaOH extractable and H₂SO₄ extractable) in hyporheic sediments from the gravel bars. Dissolved phosphorus was the major contributor to TP (74–79%) in both interstitial and surface waters on all sampling dates, and in most cases surface water P concentrations were significantly higher than interstitial concentrations. Hyporheic sediment TP concentrations ranged between 269 and 465 µg g^?1 and were highest in fine sediment fractions. Acid‐extractable P, a non‐bioavailable form, represented at least 95% of sediment TP. A positive relationship was observed between VHG and TP in two of the gravel bars, with wells that were strongly downwelling having lower TP concentrations. These results suggest that in downwelling zones, hyporheic sediments can trap surface‐derived dissolved P, and that much of this P becomes stored in refractory particulate forms. Bioavailable P is mainly present in dissolved form and only occupies a small fraction of total P, with particulate P comprising the majority of total P. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Assessing climate change impacts on European wind energy from ENSEMBLES high-resolution climate projections     

Isabelle Tobin  Robert Vautard  Irena Balog  François-Marie Bréon  Sonia Jerez  Paolo Michele Ruti  Françoise Thais  Mathieu Vrac  Pascal Yiou 《Climatic change》2015,128(1-2):99-112

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Reconstructing the subsurface ocean decadal variability using surface nudging in a perfect model framework     

Jérôme Servonnat  Juliette Mignot  Eric Guilyardi  Didier Swingedouw  Roland Séférian  Sonia Labetoulle 《Climate Dynamics》2015,44(1-2):315-338

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Collisions of two solid bodies in Keplerian orbits; new orbits and systematic effects     

Sonia Clairemidi  Françoise Depasse 《Earth, Moon, and Planets》1987,39(1):37-50

It has been shown in various papers dealing with systems of colloding bodies in a Keplerian field that the dynamical evolution does not depend only on the initial orbital conditions. This is a consequence of the wide range of orbits generated by the collision process. From the study of a few pairs of orbits we examine what factors which produce that variety of orbits, and search for systematic effects. The role of the positions along the orbits, of inelasticity, of size, of mass and of relative inclination is emphasized.  相似文献   

Geotechnical instrumentation for monitoring field performance. John Dunnicliff with the assistance of Gordon E. Green,A Wiley-Interscience Publication, 1988. ISBN 0-471-00546-0. Number of pages: 577     

Sonia H. Armaleh 《国际地质力学数值与分析法杂志》1995,19(3):227-227

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Integrated provenance and detrital thermochronology studies on the ANDRILL AND‐2A drill core: Late Oligocene–Early Miocene exhumation of the Transantarctic Mountains (southern Victoria Land,Antarctica)     

Massimiliano Zattin  Franco M. Talarico  Sonia Sandroni 《地学学报》2010,22(5):361-368

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