Influence of metal oxides in the colorimetric determination of acid volatile sulfide in sediments     

Janaina L. Oliveira  Alessandra Eugênio  Júlio C. Rodrigues de Azevedo  Jorge Nozaki 《洁净——土壤、空气、水》2006,34(4):383-388

The sediment of Lagoa dos Patos‐MS, Brazil, was investigated to verify the influence of metal sulfides and oxyhydroxides of Mn and Fe on the heavy metal availability. The spectrophotometric method of methylene blue was used, with 8 interlinked tubes containing the samples with SnCl₂, where N₂ was introduced to release the H₂S extracted with 6.0 mol L^–1 HCl, and trapped in 0.05 M NaOH solution. The influence of SO₄^2–, Mn(IV) and Fe(III) oxyhydroxides was investigated with samples constituted by a mixture of MnO₂; Na₂SO₄; FeCl₃, and sediments. The presence of SnCl₂ was very important to avoid the interferences of iron and manganese oxyhydroxides. The method of standard addition was applied and the efficiency was (100.8 ± 9.4)%. The ratio among the quantities of metals potentially available and the acid volatile sulfide (AVS) indicate that the system presents small metals availability to the benthic community, by the existence of sulfide capable to immobilize the metal as insoluble sulfide.  相似文献   

Intercomparison of Boron Isotope and Concentration Measurements. Part II: Evaluation of Results   总被引：3，自引：1，他引：3  

Roberto Gonfiantini  Sonia Tonarini  Manfred Grning  Alessandra Adorni‐Braccesi  Assad S. Al‐Ammar  Marcus Astner  Sebastien Bchler  Ramon M. Barnes  Randy L. Bassett  Alain Cocherie  Annette Deyhle  Andrea Dini  Giorgio Ferrara  Jrme Gaillardet  Judith Grimm  Catherine Guerrot  Urs Krhenbühl  Graham Layne  Damien Lemarchand  Anette Meixner  D. Jack Northington  Maddalena Pennisi  Eva Reitznerov  Ilia Rodushkin  Naoji Sugiura  Regina Surberg  Sabine Tonn  Michael Wiedenbeck  Samuel Wunderli  Yingkai Xiao  Thomas Zack 《Geostandards and Geoanalytical Research》2003,27(1):41-57

The Istituto di Geoscienze e Georisorse (IGG), on behalf and with the support of the International Atomic Energy Agency (IAEA), prepared eight geological materials (three natural waters and five rocks and minerals), intended for a blind interlaboratory comparison of measurements of boron isotopic composition and concentration. The materials were distributed to twenty seven laboratories - virtually all those performing geochemical boron isotope analyses in the world -which agreed to participate in the intercomparison exercise. Only fifteen laboratories, however, ultimately submitted the isotopic and/or concentration results they obtained on the intercomparison materials. The results demonstrate that interlaboratory reproducibility is not well reflected by the precision values reported by the individual laboratories and this observation holds true for both boron concentration and isotopic composition. The reasons for the discrepancies include fractionations due to the chemical matrix of materials, relative shift of the zero position on the δ¹¹B scale and a lack of well characterized materials for calibrating absolute boron content measurements. The intercomparison materials are now available at the IAEA (solid materials) and IGG (waters) for future distribution.  相似文献   

Numerical investigation of the Break-down threshold for a restricted three-body problem     

Alessandra Celletti  Claude Froeschl 《Planetary and Space Science》1998,46(11-12)

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Sylvio Ferraz-Mello: Canonical Perturbation Theories. Degenerate Systems and Resonance     

Alessandra Celletti 《Celestial Mechanics and Dynamical Astronomy》2008,100(4):331-333

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New insights on late Quaternary palaeogeographic setting in the Northern Adriatic Sea (Italy)     

Sara Picone  Francesca Alvisi  Enrico Dinelli  Caterina Morigi  Alessandra Negri  Mariangela Ravaioli  Carmela Vaccaro 《第四纪科学杂志》2008,23(5):489-501

Sedimentological, geochemical and micropalaeontological data from sediment cores in the northwestern Adriatic Sea were obtained to reconstruct the stratigraphic framework and palaeogeographic setting during the last post‐glacial sea‐level rise (14000–6000 yr BP). Four lithostratigraphic units were identified: (a) distal plain deposits (>14000 yr BP), submerged during the first phases of marine ingression; (b) coastal lagoon system; (c) barrier‐lagoon system, which is dated back to between 10019 ± 61 and 10228 ± 174 cal. yr BP from ¹⁴C dating on peat and shell remains; (d) marine prodelta deposits (<5500 yr BP). Geochemical data allow the identification of three distinct sediment sources: River Po, River Adige and Eastern Alpine rivers characterised by decreasing Ni/Mg ratios (50–70, 8–15 and 5–10, respectively) and Ba/Al ratios of 45–55, 55–65 and 35–45, respectively. The three sources display different relative abundances in time. During the Lateglacial, the Po is the main sediment source for the southern cores, whereas the Eastern Alps and the River Adige are the main sediment sources for the northern cores. This suggests a northern position of the Po River bed compared to previous studies. Coastal drowning led to a homogenization of the provenance signal within the sediments. Only after the marine transgression does a River Po signal appear in the northern cores. At the same time, in the southern cores the signal of Eastern Alpine rivers becomes stronger. Transgressive barrier‐lagoon and recent sediments do not display a predominant signal for provenance indicators. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Spectral measurements of aerosol particle extinction in the 0.4–3.7 μm wavelength range, performed at Sagres with the IR‐RAD sun‐radiometer     

Vito Vitale  Claudio Tomasi  Wolfgang Von Hoyningen&#;huene  Ubaldo Bonafe  Stefano Marani  Angelo Lupi  Alessandra Cacciari  Pietro Ruggeri 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):716-733

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Local geodetic and seismic energy balance for shallow earthquake prediction     

Flavio Cannavó  Alessandra Arena  Carmelo Monaco 《Journal of Seismology》2015,19(1):1-8

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A kriging approach based on Aitchison geometry for the characterization of particle-size curves in heterogeneous aquifers   总被引：2，自引：0，他引：2  

Alessandra Menafoglio  Alberto Guadagnini  Piercesare Secchi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(7):1835-1851

We consider the problem of predicting the spatial field of particle-size curves (PSCs) from a sample observed at a finite set of locations within an alluvial aquifer near the city of Tübingen, Germany. We interpret PSCs as cumulative distribution functions and their derivatives as probability density functions. We thus (a) embed the available data into an infinite-dimensional Hilbert Space of compositional functions endowed with the Aitchison geometry and (b) develop new geostatistical methods for the analysis of spatially dependent functional compositional data. This approach enables one to provide predictions at unsampled locations for these types of data, which are commonly available in hydrogeological applications, together with a quantification of the associated uncertainty. The proposed functional compositional kriging (FCK) predictor is tested on a one-dimensional application relying on a set of 60 PSCs collected along a 5-m deep borehole at the test site. The quality of FCK predictions of PSCs is evaluated through leave-one-out cross-validation on the available data, smoothed by means of Bernstein Polynomials. A comparison of estimates of hydraulic conductivity obtained via our FCK approach against those rendered by classical kriging of effective particle diameters (i.e., quantiles of the PSCs) is provided. Unlike traditional approaches, our method fully exploits the functional form of PSCs and enables one to project the complete information content embedded in the PSC to unsampled locations in the system.  相似文献   

Sediment balances in the Blue Nile River Basin   总被引：2，自引：1，他引：1  

Yasir SAALI  Alessandra CROSATO  Yasir AMOHAMED  Seifeldin HABDALLA  Nigel GWRIGHT 《国际泥沙研究》2014,29(3):316-328

Rapid population growth in the upper Blue Nile basin has led to fast land-use changes from natural forest to agricultural land.This resulted in speeding up the soil erosion process in the highlands and increasing sedimentation further downstream in reservoirs and irrigation canals.At present,several dams are planned across the Blue Nile River in Ethiopia and the Grand Ethiopian Renaissance Dam is currently under construction near the border with Sudan.This will be the largest hydroelectric power plant in Africa.The objective of this paper is to quantify the river flows and sediment loads along the Blue Nile River network.The Soil and Water Assessment Tool was used to estimate the water flows from un-gauged sub-basins.To assess model performance,the estimated sediment loads were compared to the measured ones at selected locations.For the gauged sub-basins,water flows and sediment loads were derived from the available flow and sediment data.To fill in knowledge gaps,this study included a field survey in which new data on suspended solids and flow discharge were collected along the Blue Nile and on a number of tributaries.The comparison between the results of this study and previous estimates of the sediment load of the Blue Nile River at El Deim,near the Ethiopian Sudanese border,show that the sediment budgets have the right order of magnitude,although some uncertainties remain.This gives confidence in the results of this study providing the first sediment balance of the entire Blue Nile catchment at the sub-basin scale.  相似文献   

Carbon in Meteoroids: Wild 2 Dust Analyses, IDPs and Cometary Dust Analogues     

Alessandra Rotundi  Frans J. M. Rietmeijer 《Earth, Moon, and Planets》2008,102(1-4):473-483

Assuming that similar organic components as in comet 81P/Wild 2 are present in incoming meteoroids, we try to anticipate the observable signatures they would produce for meteor detection techniques. In this analysis we consider the elemental and organic components in cometary aggregate interplanetary dust particles and laboratory analyses of inter- and circumstellar carbon dust analogues. On the basis of our analysis we submit that (semi) quantitative measurements of H, N and C produced during meteor ablation will open an entire new aspect to using meteoroids as tracers of these volatile element abundances in active comets and their contributions to the mesospheric metal layers.  相似文献