Chemical Reduction of Hexavalent Chromium Present in Contaminated Soil using a Packed-bed Column Reactor     

Débora V. Franco  Leonardo M. Da Silva  Wilson F. Jardim 《洁净——土壤、空气、水》2009,37(11):858-865

Soil samples extracted from a contaminated landfill with hexavalent chromium, Cr(VI), were treated in a packed-bed column reactor applying different reductant solutions under controlled flow conditions. In all cases, the kinetic study concerning removal of Cr(VI) from packed soil revealed the overall process (leaching and redox reaction) is described by pseudo-first order kinetics. The complexity of the process taking place in non-isotropic medium (packed soil) was evidenced by dependence of the overall pseudo-first order kinetic rate constant, k*, on treatment time, volumetric flow rate, and composition and concentration of the reductant solution. A phenomenological equation was proposed in order to represent k* in non-ideal conditions. The comparative study concerning the use of different reductants revealed application of ferrous sulphate, Fe(II), under flow conditions furnished the best results, since in this case the redox process reached a considerable extent and the reduced chromium, Cr(III), was immobilized in packed soil as an insoluble mixed compound.  相似文献   

Pier scour monitoring system by bed-level image tracking     

Wen-Yi CHANG  Jihn-Sung LAI  Teng-Yi YU  Franco LIN  Lung-Cheng LEE  Whey-Fone TSAI  Chin-Hsiung LOH 《国际泥沙研究》2014,29(2):269-277

A scour monitoring system with a micro camera tracking the bed-level images is proposed in this study.Two image recognition algorithms have been developed to support the bed-level image tracking approach.Through the laboratory experiments of pier scour,this study demonstrates that the proposed system is able to accurately monitor the scour-depth evolution in real time.In addition,five commonly-used temporal scour models are employed to simulate scour-depth evolution and their results are compared with monitoring data.In general,the results indicate that the proposed scour monitoring system has the potential for further applications in the field.  相似文献   

Erratum to: Second California Assessment: integrated climate change impacts assessment of natural and managed systems. Guest editorial     

Guido Franco  Daniel R. Cayan  Susanne Moser  Michael Hanemann  Myoung-Ae Jones 《Climatic change》2012,113(3-4):1099-1100

  相似文献   

Evolution of fluid geochemistry at the Turrialba volcano (Costa Rica) from 1998 to 2008   总被引：3，自引：1，他引：2  

O. Vaselli  Franco Tassi  E. Duarte  E. Fernandez  R. J. Poreda  A. Delgado Huertas 《Bulletin of Volcanology》2010,72(4):397-410

Turrialba (10°02′N, 83°45′W) is a 3,349-m high stratovolcano belonging to the Holocene “Cordillera Central” volcanic belt of Costa Rica. The summit consists of three EW-oriented craters (East, Central, and West). Since its last eruptive phase (1864–1866), the Central and West craters have displayed modest fumarolic activity, with outlet temperatures clustering around 90°C. In 2001, seismic swarms, ground deformation, and increasing fumarolic activity occurred. From 2005 to 2008, new fumarolic vents opened between and within the Central and West craters, and along the western and southwestern outer flanks of the volcanic edifice. These physical changes were accompanied by a drastic modification in the gas chemistry that can be divided in three stages: (1) hydrothermal (from 1998 to autumn 2001), characterized by the presence of H₂O, CO₂, H₂S, and, to a very minor extent, HCl and HF; (2) hydrothermal/magmatic (autumn 2001–2007), with the appearance of SO₂ and a significant increase of HCl and HF; and (3) magmatic-dominated (2007–2008), characterized by increased SO₂ content, SO₂/H₂S > 100, and temperatures up to 282°C. Accordingly, gas equilibrium in the CO₂-CH₄-H₂ system suggests a progressive evolution of the deep fluid reservoir toward higher temperatures and more oxidizing conditions. The chemical–physical modifications of Turrialba in the last decade can be interpreted as part of a cyclic mechanism controlling the balance between the hydrothermal and the magmatic systems. Nevertheless, the risk of rejuvenation of the volcanic activity cannot be excluded, and an appropriate seismic, ground deformation, and geochemical monitoring program is highly recommended. Turrialba lies at a distance of 35 and 15 km from San José and Cartago, respectively, the two largest cities in Costa Rica.  相似文献   

Biochemical and microbial features of shallow marine sediments along the Terra Nova Bay (Ross Sea,Antarctica)   总被引：1，自引：0，他引：1  

Franco Baldi  Davide Marchetto  Francesco Pini  Renato Fani  Luigi Michaud  Angelina Lo Giudice  Daniela Berto  Michele Giani 《Continental Shelf Research》2010

Shallow marine sediments were collected from seven stations (three of which located at Gerlache Inlet, two at Tethys Bay, one at Adelie Cove and one just beneath the Italian Research Base) along the Terra Nova Bay coast (Ross Sea, Antarctica). Their chemical, biochemical and microbiological properties were studied in order to provide further insights in the knowledge of this Antarctic benthic ecosystem. Overall, the organic carbon (OC) represented the major fraction of total carbon (TC) and displayed concentrations similar to or slightly lower than those previously measured in Antarctic bottom sediments. The biopolymeric carbon within OC ranged from 4.1% to 19.9% and showed a wide trophic range (65–834 μg g⁻¹ d.w.). Proteins (PRT) represented on average the main biochemical class contributing to labile organic carbon, followed by lipids (LIP) and carbohydrates (CHO). The activity of aminopeptidase, β-d-glucosidase, alkaline phosphatase and esterase was checked, giving the highest values at Tethys Bay and at the deepest water sediments. The principal component analysis, which was computed considering physical, chemical (elemental and biochemical sedimentary composition) and microbiological parameters (including bacterial abundance, ectoenzymatic activities, T-RFs richness and diversity indices), allowed to obtain two main clusters (“Tethys Bay” and “other stations”). Based on data obtained, two representative 16S rRNA clone libraries using samples from Tethys Bay and Gerlache Inlet were constructed. The sequences of 171 clones were compared to those available in public databases to determine their approximate phylogenetic affiliations. Both aerobic and anaerobic bacteria were disclosed, with the majority of them affiliated with the Gamma- and Deltaproteobacteria, Bacteroidetes and Acidobacteria. The occurrence of strictly anaerobic bacteria suggests that sediments might also undergo anoxic conditions that, in turn, could favor the accumulation of PRT in respect to CHO, assuming that fermentation of amino acids is slower than that of sugars from decomposing polysaccharides.  相似文献   

Electrochemical Ozone Production as an Environmentally Friendly Technology for Water Treatment     

Débora V. Franco  Wilson F. Jardim  Julien F. C. Boodts  Leonardo M. Da Silva 《洁净——土壤、空气、水》2008,36(1):34-44

Perspectives, advances and environmental aspects concerning electrochemical ozone production applied to water purification are presented and discussed in relation to the conventional corona process (silent electric discharge). Ozone generated using a laboratory‐made electrochemical reactor was applied for the discoloration/degradation of dyes used in the Brazilian textile industry and for degradation of endocrine disruptors. A constant ozone load of 0.35 ± 0.02 g/h was used throughout. The study, concerning color removal from dye solutions, revealed that total discoloration is rapidly achieved. The degradation rate of the textile dyes evaluated by TOC is little affected by the dye composition and considerably influenced by the pH and ozonation time. Analysis of the COD/TOC‐ratio indicates that ozonation increases oxidation feasibility of the organic matter (dye by‐products) when compared to the original compounds. Ozonation of mixed aqueous solutions containing different endocrine disruptors revealed these compounds are totally degraded with a very high removal rate.  相似文献   

Respiration partitioning in contrasting subtidal sediments: seasonality and response to a spring phytoplankton deposition     

Maria de Assunção Franco  Jan Vanaverbeke  Dick Van Oevelen  Karline Soetaert  Maria José Costa  Magda Vincx  Tom Moens 《Marine Ecology》2010,31(2):276-290

Biomass and respiration rates of bacteria, nematodes and macrobenthos were estimated in relation to the deposition of the spring phytoplankton bloom at two contrasting sites in the Southern North Sea: one with fine‐grained sediment close to the coastline and another with highly permeable sediments. Sediment community oxygen consumption (SCOC) was also measured. Bacterial biomass was relatively similar at both stations, whereas nematode and macrobenthic biomass were higher in fine‐grained sediment. In fine sediments, bacterial biomass increased quickly after deposition of the phytoplankton bloom, whereas the response of nematodes and macrobenthos was delayed. In coarser sediments, nematodes and macrobenthos also showed a fast response in terms of density and biomass. Respiration in permeable sediments was mainly dominated by bacteria at all periods of the year. Hence, nematode and macrobenthic respiration did not contribute strongly to SCOC. This is in contrast to the patterns observed in finer sediments, where both macrofauna and nematodes were important oxygen consumers as well. Macrobenthos contributed more to total SCOC than did nematodes in winter. However, shortly after the arrival of phytodetritus at the sea floor, nematodes and macrobenthos contributed equally to the total SCOC, indicating that all benthic size classes should be taken into account when investigating marine benthic respiration rates.  相似文献   

Origin of talc in the Ionian Sea waters     

Renzo Sartori  Luciano Tomadin 《Marine Geology》1977,25(4):M13-M18

Talc and/or pyrophyllite have been detected as suspended particulates in the waters of the Ionian Sea (eastern Mediterranean). Differing from similar findings reported in some recent works by many authors, the presence of these silicates is completely attributable to unavoidable contamination during collection and analytical processing of the water samples.  相似文献   

Fluidization： An Important Process in the Formation of the Qiyugou Au-bearing Breccia Pipes in Central China   总被引：2，自引：0，他引：2  

ZHANG Yuanhou ZHANG Shihong Franco PIRAJNO 《《地质学报》英文版》2007,81(2):226-238

Fluidization processes based on experiments are reviewed to gain some useful insights and comparisons with those that occur in hydrothermal systems. Field and petrographic work, and microscope observation were carried out on samples from the Qiyugou Au-bearing breccia pipes from the East Qinling region, Henan Province. Evidence from macro- and micro-textures suggests that the style of breccias in the Qiyugou area can be grouped into three types： （1） jigsaw fit-stockwork texture, in which the interval between clasts is marked by fractures or filled with calcite or quartz veins; （2） larger breccias that are supported by smaller breccias, rock flour and alteration materials; in this type clasts moved over short distances, creating open spaces; （3） fluidized texture, where the clasts of different lithologies have rounded shapes. These observations are compared with those resulting from experiments on fluidization processes. The results of this comparison suggest that fluidization is an important geological process in the formation of the Qiyugou Au-bearing breccia pipes and gold mineralization. In addition, fluidization processes such as expansion, bubbling, slugging, channeling and spouting must have contributed to the formation of the pipes and were conducive to the development of gold mineralization. In the Qiyugou breccia pipes, gold mineralization occurs as disseminations, in stockwork veins, and open space infills. The ore zones form subparallel sheets that are nearly perpendicular to the walls of the pipes.  相似文献   

Pressure and density gradients in H II Regions     

José Franco  Stan E. Kurtz  José A. GarcÍa-Barreto  Guillermo GarcÍa-Segura  Eduardo de la Fuente  Peter Hofner  Alejandro Esquivel 《Astrophysics and Space Science》2001,277(1):71-74

Here we discuss the effects of large ambient pressures and decreasing density gradients on the observed properties of dusty UC hii regions. Dust absorption can effectively reduce the size of the photo ionized region, and density gradients can modify the spectral index of the emission. The effects of the density gradients seem to be present in both galactic and extragalactic HII regions.  相似文献