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1.
Sci Total Environ ; 927: 172257, 2024 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-38608912

RESUMO

Waterborne pathogens threaten 2.2 billion people lacking access to safely managed drinking water services, causing over a million annual diarrheal deaths. Individuals without access to chlorine reagents or filtration devices often resort to do-it-yourself (DIY) methods, such as boiling or solar disinfection (SODIS). However, these methods are not simple to implement. In this study, we introduced an innovative and easily implemented disinfection approach. We discovered that immersing aluminum foil in various alkaline solutions produces alkali-treated aluminum foil (ATA foil) that effectively adsorbs Escherichia coli (E. coli), Salmonella, and Acinetobacter through the generated surface aluminum hydroxide. For example, a 25 cm2 ATA foil efficiently captures all 104E. coli DH5α strains in 100 mL water within 30 min. Using a saturated suspension of magnesium hydroxide, a type of fertilizer, as the alkaline solution, the properties of the saturated suspension eliminate the need for measuring reagents or changing solutions, making it easy for anyone to create ATA foil. ATA foils can be conveniently produced within mesh bags and placed in household water containers, reducing the risk of recontamination. Replacing the ATA foil with a foil improves the adsorption efficiency, and re-immersing the used foil in the production suspension restores its adsorption capacity. Consequently, ATA foil is an accessible and user-friendly alternative DIY method for underserved communities. Verification experiments covering variations in the water quality and climate are crucial for validating the efficacy of the foil. Fortunately, the ATA foil, with DIY characteristics similar to those of boiling and SODIS, is well-suited for testing under diverse global conditions, offering a promising solution for addressing waterborne pathogens worldwide.


Assuntos
Desinfecção , Água Potável , Purificação da Água , Água Potável/microbiologia , Água Potável/química , Desinfecção/métodos , Purificação da Água/métodos , Microbiologia da Água , Abastecimento de Água
2.
Zoological Lett ; 9(1): 18, 2023 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-37789380

RESUMO

The environment around deep sea hydrothermal vents is characterized by an abundance of sulfur compounds, including toxic hydrogen sulfide. However, numerous communities of various invertebrates are found in it. It is suggested that invertebrates in the vicinity of hydrothermal vents detoxify sulfur compounds by biosynthesis of taurine-related compounds in the body. On the other hand, the vent endemic polychaete Alvinella pompejana has spherocrystals composed of sulfur and other metals in its digestive tract. It was considered that the spherocrystals contribute to the regulation of sulfur in body fluids. Paralvinella spp. and Polynoidae. gen. sp. live sympatrically and in areas most affected by vent fluid. In this study, we focused on the digestive tract of Paralvinella spp. and Polynoidae. gen. sp. to examine whether they have spherocrystals. We also investigated the possible involvement of bacteria in the digestive tract in spherulization. Examination with a scanning electron microscope (SEM) equipped with Energy Disperse X-ray Spectroscopy (EDS) detected spherocrystals containing sulfur and iron in the digestive tract of Paralvinella spp. In contrast, such spherocrystals were not observed in that of Polynoidae. gen. sp. although sulfur is detected there by inductively coupled plasma-optical emission spectrometry (ICP-OES). Meta-16S rRNA analysis indicated that the floras of the digestive tracts of the two species were very similar, suggesting that enteric bacteria are not responsible for spherocrystal formation. Analysis of taurine-related compounds indicated that the digestive tissues of Polynoidae. gen. sp. contain a higher amount of hypotaurine and thiotaurine than those of Paralvinella spp. Therefore, the two sympatric polychaetes use different strategies for controlling sulfur, i.e., Paralvinella spp. forms spherocrystals containing elemental sulfur and iron in the digestive tract, but Polynoidae. gen. sp. accumulates taurine-related compounds instead of spherocrystals. Such differences may be related to differences in their lifestyles, i.e., burrow-dweller or free-moving, or may have been acquired phylogenetically in the evolutionary process.

3.
Commun Biol ; 3(1): 136, 2020 04 02.
Artigo em Inglês | MEDLINE | ID: mdl-32242062

RESUMO

The upper oceanic crust is mainly composed of basaltic lava that constitutes one of the largest habitable zones on Earth. However, the nature of deep microbial life in oceanic crust remains poorly understood, especially where old cold basaltic rock interacts with seawater beneath sediment. Here we show that microbial cells are densely concentrated in Fe-rich smectite on fracture surfaces and veins in 33.5- and 104-million-year-old (Ma) subseafloor basaltic rock. The Fe-rich smectite is locally enriched in organic carbon. Nanoscale solid characterizations reveal the organic carbon to be microbial cells within the Fe-rich smectite, with cell densities locally exceeding 1010 cells/cm3. Dominance of heterotrophic bacteria indicated by analyses of DNA sequences and lipids supports the importance of organic matter as carbon and energy sources in subseafloor basalt. Given the prominence of basaltic lava on Earth and Mars, microbial life could be habitable where subsurface basaltic rocks interact with liquid water.


Assuntos
Bactérias/crescimento & desenvolvimento , Sedimentos Geológicos/microbiologia , Processos Heterotróficos , Silicatos , Bactérias/genética , Bactérias/metabolismo , Carbono/metabolismo , Metabolismo Energético , Metabolismo dos Lipídeos , Microbiota , Oceano Pacífico , Ribotipagem
4.
Nat Commun ; 10(1): 400, 2019 02 06.
Artigo em Inglês | MEDLINE | ID: mdl-30728355

RESUMO

Ferromanganese minerals are widely distributed in subseafloor sediments and on the seafloor in oceanic abyssal plains. Assessing their input, formation and preservation is important for understanding the global marine manganese cycle and associated trace elements. However, the extent of ferromanganese minerals buried in subseafloor sediments remains unclear. Here we show that abundant (108-109 particles cm-3) micrometer-scale ferromanganese mineral particles (Mn-microparticles) are found in the oxic pelagic clays of the South Pacific Gyre (SPG) from the seafloor to the ~100 million-year-old sediments above the basement. Three-dimensional micro-texture, and major and trace element compositional analyses revealed that these Mn-microparticles consist of poorly crystalline ferromanganese oxides precipitating from bottom water. Based on our findings, we extrapolate that 1.5-8.8 × 1028 Mn-microparticles, accounting for 1.28-7.62 Tt of manganese, are globally present in oxic subseafloor sediments. This estimate is at least two orders of magnitude larger than the manganese budget for nodules and crusts on the seafloor. Subseafloor Mn-microparticles thus contribute significantly to the global manganese budget.

5.
Microbes Environ ; 33(2): 214-221, 2018 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-29887548

RESUMO

In the present study, the influence of the co-contamination with various chemical forms of antimony (Sb) with arsenite (As[III]) on soil microbial communities was investigated. The oxidation of As(III) to As(V) was monitored in soil columns amended with As(III) and three different chemical forms of Sb: antimony potassium tartrate (Sb[III]-tar), antimony(III) oxide (Sb2O3), and potassium antimonate (Sb[V]). Soil microbial communities were examined qualitatively and quantitatively using 16S rDNA- and arsenite oxidase gene (aioA)-targeted analyses. Microbial As(III) oxidation was detected in all soil columns and 90-100% of added As(III) (200 µmol L-1) was oxidized to As(V) in 9 d, except in the Sb(III)-tar co-amendments that only oxidized 30%. 16S rDNA- and aioA-targeted analyses showed that the presence of different Sb chemical forms significantly affected the selection of distinct As(III)-oxidizing bacterial populations. Most of the 16S rRNA genes detected in soil columns belonged to Betaproteobacteria and Gammaproteobacteria, and some sequences were closely related to those of known As(III) oxidizers. Co-amendments with Sb(III)-tar and high concentrations of Sb2O3 significantly increased the ratios of aioA-possessing bacterial populations, indicating the enrichment of As(III) oxidizers resistant to As and Sb toxicity. Under Sb co-amendment conditions, there was no correlation between aioA gene abundance and the rates of As(III) oxidation. Collectively, these results demonstrated that the presence of different Sb chemical forms imposed a strong selective pressure on the soil bacterial community and, thus, the co-existing metalloid is an important factor affecting the redox transformation of arsenic in natural environments.


Assuntos
Antimônio/química , Arsenitos/química , Bactérias/metabolismo , Microbiologia do Solo , Poluentes do Solo/química , Solo/química , Antimônio/análise , Tartarato de Antimônio e Potássio/análise , Tartarato de Antimônio e Potássio/química , Arsenitos/análise , Bactérias/genética , Monitoramento Ambiental , Oxirredução , Óxidos/análise , Óxidos/química , Oxirredutases/genética , RNA Ribossômico 16S/genética , Poluentes do Solo/análise
6.
Genome Announc ; 6(20)2018 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-29773618

RESUMO

Mariprofundus micogutta strain ET2 was isolated in 2014 from a deep-sea hydrothermal field on the Bayonnaise Knoll of the Izu-Ogasawara arc. Here, we report its draft genome, which comprises 2,497,805 bp and contains 2,417 predicted coding sequences.

7.
J Water Health ; 16(1): 159-163, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29424729

RESUMO

Although many kinds of materials for water purification are known, easy-to-use methods that ensure the safety of drinking water for rural populations are not sufficiently available. Sorbent-embedded sheets provide methods for the easy removal of contaminants from drinking water in the home. As an example of such a sorbent-embedded sheet, we prepared a Linde type A (LTA) zeolite-embedded sheet (ZES) and examined its Pb(II) removal behaviour. Different amounts of LTA were added either as powder or as ZES to 0.3 mM Pb(NO3)2 solutions containing 2.5 mM Ca(NO3)2, in which the ratio of the negative charges in LTA to the positive charges in Pb(II) (LTA/Pb ratio) ranged from 1 to 20. After shaking, the mixtures were centrifuged to remove the powder, while the ZES was simply removed from the mixture by hand. The LTA powder removed more than 99% of the Pb(II) from the solution at all LTA/Pb ratios within 1 h, while the ZES removed >99% of the Pb(II) at LTA/Pb ratios of 2 and higher; at the highest LTA/Pb ratio of 20, the ZES removed >99% of the Pb(II) in 30 s. Therefore, the use of appropriate sorbent-embedded sheets enable the facile removal of contaminants from water.


Assuntos
Países em Desenvolvimento , Água Potável/química , Chumbo/química , Poluentes Químicos da Água/química , Purificação da Água/instrumentação , Zeolitas/farmacologia , Adsorção , Qualidade da Água
8.
Microbes Environ ; 32(3): 283-287, 2017 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-28781344

RESUMO

Natural bacteriogenic iron oxides (BIOS) were investigated using local-analyzable synchrotron-based scanning transmission X-ray microscopy (STXM) with a submicron-scale resolution. Cell, cell sheath interface (EPS), and sheath in the BIOS were clearly depicted using C-, N-, and O- near edge X-ray absorption fine structure (NEXAFS) obtained through STXM measurements. Fe-NEXAFS obtained from different regions of BIOS indicated that the most dominant iron mineral species was ferrihydrite. Fe(II)- and/or Fe(III)-acidic polysaccharides accompanied ferrihydrite near the cell and EPS regions. Our STXM/NEXAFS analysis showed that Fe species change continuously between the cell, EPS, and sheath under several 10-nm scales.


Assuntos
Bactérias , Compostos Férricos/análise , Ferro , Síncrotrons , Espectroscopia por Absorção de Raios X
9.
J Hazard Mater ; 322(Pt A): 318-324, 2017 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-26412016

RESUMO

This study investigated how silver nanoparticles (AgNP) and ionic silver (AgNO3) undergo phase-transformations in soils under aerobic and anaerobic conditions using extended X-ray absorption fine structure (EXAFS) spectroscopy. After 30 days of aerobic incubation, 88% of AgNP added to the soil remained persistent, whereas AgNO3 was completely transformed into Ag associated with humus and clay minerals. In the anaerobic soil, 83% of the spiked AgNP was transformed into Ag2S, accompanied by significant decrease in water- and acid-extractable Ag fractions. About 50% of AgNO3 spiked to the anaerobic soil underwent transformations into metallic Ag and associations with clay minerals. Oxide (Ag2O) and carbonate (Ag2CO3) forms of Ag were not predominant in aerobic and anaerobic soils. The redox potential of soil had a profound effect on determination of the phase-transformation pathways for AgNP and ionic Ag.

10.
Arch Microbiol ; 199(2): 335-346, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-27766355

RESUMO

A novel iron-oxidizing chemolithoautotrophic bacterium, strain ET2T, was isolated from a deep-sea sediment in a hydrothermal field of the Bayonnaise knoll of the Izu-Ogasawara arc. Cells were bean-shaped, curved short rods. Growth was observed at a temperature range of 15-30 °C (optimum 25 °C, doubling time 24 h) and a pH range of 5.8-7.0 (optimum pH 6.4) in the presence of NaCl at a range of 1.0-4.0 % (optimum 2.75 %). The isolate was a microaerophilic, strict chemolithoautotroph capable of growing using ferrous iron and molecular oxygen (O2) as the sole electron donor and acceptor, respectively; carbon dioxide as the sole carbon source; and either ammonium or nitrate as the sole nitrogen source. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that the new isolate was related to the only previously isolated Mariprofundus species, M. ferrooxydans. Although relatively high 16S rRNA gene similarity (95 %) was found between the new isolate and M. ferrooxydans, the isolate was distinct in terms of cellular fatty acid composition, genomic DNA G+C content and cell morphology. Furthermore, genomic comparison between ET2T and M. ferrooxydans PV-1 indicated that the genomic dissimilarity of these strains met the standard for species-level differentiation. On the basis of its physiological and molecular characteristics, strain ET2T (= KCTC 15556T = JCM 30585 T) represents a novel species of Mariprofundus, for which the name Mariprofundus micogutta is proposed. We also propose the subordinate taxa Mariprofundales ord. nov. and Zetaproteobacteria classis nov. in the phylum Proteobacteria.


Assuntos
Proteobactérias/classificação , Proteobactérias/isolamento & purificação , Água do Mar/microbiologia , Crescimento Quimioautotrófico , Ácidos Graxos/análise , Fontes Hidrotermais , Ferro/metabolismo , Filogenia , Proteobactérias/genética , Proteobactérias/metabolismo , RNA Ribossômico 16S/genética
11.
Microbes Environ ; 31(3): 329-38, 2016 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-27592518

RESUMO

Accretionary prisms are mainly composed of ancient marine sediment scraped from the subducting oceanic plate at a convergent plate boundary. Large amounts of anaerobic groundwater and natural gas, mainly methane (CH4) and nitrogen gas (N2), are present in the deep aquifers associated with an accretionary prism; however, the origins of these gases are poorly understood. We herein revealed regional variations in CH4 and N2 production processes in deep aquifers in the accretionary prism in Southwest Japan, known as the Shimanto Belt. Stable carbon isotopic and microbiological analyses suggested that CH4 is produced through the non-biological thermal decomposition of organic matter in the deep aquifers in the coastal area near the convergent plate boundary, whereas a syntrophic consortium of hydrogen (H2)-producing fermentative bacteria and H2-utilizing methanogens contributes to the significant production of CH4 observed in deep aquifers in midland and mountainous areas associated with the accretionary prism. Our results also demonstrated that N2 production through the anaerobic oxidation of organic matter by denitrifying bacteria is particularly prevalent in deep aquifers in mountainous areas in which groundwater is affected by rainfall.


Assuntos
Água Subterrânea/microbiologia , Metano/metabolismo , Nitrogênio/metabolismo , Anaerobiose , Isótopos de Carbono/análise , Hidrogênio/metabolismo , Marcação por Isótopo , Japão
12.
Appl Environ Microbiol ; 82(19): 5741-55, 2016 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-27422841

RESUMO

UNLABELLED: It has been suggested that iron is one of the most important energy sources for photosynthesis-independent microbial ecosystems in the ocean crust. Iron-metabolizing chemolithoautotrophs play a key role as primary producers, but little is known about their distribution and diversity and their ecological role as submarine iron-metabolizing chemolithotrophs, particularly the iron oxidizers. In this study, we investigated the microbial communities in several iron-dominated flocculent mats found in deep-sea hydrothermal fields in the Mariana Volcanic Arc and Trough and the Okinawa Trough by culture-independent molecular techniques and X-ray mineralogical analyses. The abundance and composition of the 16S rRNA gene phylotypes demonstrated the ubiquity of zetaproteobacterial phylotypes in iron-dominated mat communities affected by hydrothermal fluid input. Electron microscopy with energy-dispersive X-ray microanalysis and X-ray absorption fine structure (XAFS) analysis revealed the chemical and mineralogical signatures of biogenic Fe-(oxy)hydroxide species and the potential contribution of Zetaproteobacteria to the in situ generation. These results suggest that putative iron-oxidizing chemolithoautotrophs play a significant ecological role in producing iron-dominated flocculent mats and that they are important for iron and carbon cycles in deep-sea low-temperature hydrothermal environments. IMPORTANCE: We report novel aspects of microbiology from iron-dominated flocculent mats in various deep-sea environments. In this study, we examined the relationship between Zetaproteobacteria and iron oxides across several hydrothermally influenced sites in the deep sea. We analyzed iron-dominated mats using culture-independent molecular techniques and X-ray mineralogical analyses. The scanning electron microscopy-energy-dispersive X-ray spectroscopy SEM-EDS analysis and X-ray absorption fine structure (XAFS) analysis revealed chemical and mineralogical signatures of biogenic Fe-(oxy)hydroxide species as well as the potential contribution of the zetaproteobacterial population to the in situ production. These key findings provide important information for understanding the mechanisms of both geomicrobiological iron cycling and the formation of iron-dominated mats in deep-sea hydrothermal fields.


Assuntos
Compostos Férricos/metabolismo , Fontes Hidrotermais/microbiologia , Ferro/metabolismo , Proteobactérias/classificação , Microbiota , Oxirredução , Oceano Pacífico , Proteobactérias/genética , Proteobactérias/metabolismo , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Análise de Sequência de RNA , Espectroscopia por Absorção de Raios X
13.
Microbes Environ ; 31(1): 63-9, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26947441

RESUMO

We herein investigated the mechanisms underlying the contact leaching process in pyrite bioleaching by Acidithiobacillus ferrooxidans using scanning transmission X-ray microscopy (STXM)-based C and Fe near edge X-ray absorption fine structure (NEXAFS) analyses. The C NEXAFS analysis directly showed that attached A. ferrooxidans produces polysaccharide-abundant extracellular polymeric substances (EPS) at the cell-pyrite interface. Furthermore, by combining the C and Fe NEXAFS results, we detected significant amounts of Fe(II), in addition to Fe(III), in the interfacial EPS at the cell-pyrite interface. A probable explanation for the Fe(II) in detected EPS is the leaching of Fe(II) from the pyrite. The detection of Fe(II) also indicates that Fe(III) resulting from pyrite oxidation may effectively function as an oxidizing agent for pyrite at the cell-pyrite interface. Thus, our results imply that a key role of Fe(III) in EPS, in addition to its previously described role in the electrostatic attachment of the cell to pyrite, is enhancing pyrite dissolution.


Assuntos
Acidithiobacillus/metabolismo , Biopolímeros/química , Biopolímeros/metabolismo , Microbiologia Ambiental , Ferro/análise , Sulfetos/metabolismo , Microanálise por Sonda Eletrônica , Ferro/metabolismo , Microscopia Eletrônica de Transmissão e Varredura , Oxirredução
14.
Environ Sci Technol ; 47(17): 9660-7, 2013 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-23909642

RESUMO

In this study, we investigated the behavior of Sb(V) during the transformation of poorly crystalline Fe(III) oxyhydroxides (two-line ferrihydrite) with various Sb/Fe molar ratios at pH 6.0. Both XRD and Fe EXAFS analyses confirmed that goethite and hematite are the primary transformation products of the ferrihydrite in the presence of Sb(V). The crystallization kinetics showed that the transformation rate with Sb(V) was approximately the same as that of the control (without Sb(V)), which indicates that the presence of Sb(V) does not influence the transformation rate to a noticeable extent. Throughout the transformation, Sb(V) dominantly partitioned in the solid phase and no desorption of Sb(V) was observed. Furthermore, Sb EXAFS analyses suggested that Sb(V) in the solid phase is structurally incorporated into crystalline goethite and/or hematite generated by the ferrihydrite transformation. Hence, Sb(V) transfers into the thermodynamically stable solids from the metastable ferrihydrite with aging, indicating a rigid immobilization of Sb(V). These findings are valuable for making predictions on the long-term fate of Sb associated with ferrihydrite in natural environments.


Assuntos
Antimônio/química , Poluentes Ambientais/química , Compostos Férricos/química , Cristalização , Monitoramento Ambiental , Compostos de Ferro/química , Cinética , Minerais/química , Termodinâmica , Espectroscopia por Absorção de Raios X
15.
Environ Sci Technol ; 46(6): 3304-11, 2012 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-22360427

RESUMO

Ubiquitous presence of microbes in aquatic systems and their inherent ability of biomineralization make them extremely important agents in the geochemical cycling of inorganic elements. However, the detailed mechanisms of environmental biomineralization (e.g., the actual reaction rates, the temporal and spatial dynamics of these processes) are largely unknown, because there are few adequate analytical techniques to observe the biogenic oxidation/reduction reactions in situ. Here, we report a novel technical approach to characterize specific biominerals associated with a target microbe on high spatial resolution. The technique was developed by combining directly in situ phylogenetic analysis, fluorescence in situ hybridization (FISH), with a synchrotron microprobe method, micro X-ray absorption fine structure spectroscopy (µ-XAFS), and was applied to iron mineral deposition by iron(II)-oxidizing bacteria (IOB) in environmental samples. In situ visualization of microbes revealed that in natural iron mats, Betaproteobacteria dominated by IOB were dominantly localized within 10 µm of the surface. Furthermore, in situ chemical speciation by the synchrotron microprobe suggested that the Fe local structure at the IOB accumulating parts was dominantly composed of short-ordered Fe-O(6) linkage, which is not observed in bulk iron mat samples. The present study indicates that coupled XAFS-FISH could be a potential technique to provide direct information on specific biogenic reaction mediated by target microorganism.


Assuntos
Bactérias/metabolismo , Compostos Férricos/metabolismo , Bactérias/classificação , Bactérias/genética , Hibridização in Situ Fluorescente , Filogenia , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Síncrotrons , Espectroscopia por Absorção de Raios X
16.
Environ Sci Technol ; 44(10): 3712-8, 2010 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-20426473

RESUMO

In this study, we investigated local structures of Sb species in synthetic Sb(V)-coprecipitated and -adsorbed ferrihydrite and goethite, which are common iron(III) oxyhydroxides in environment, at various Sb/Fe molar ratios by extended X-ray absorption fine structure (EXAFS) analyses. The EXAFS analyses showed that Sb(V) is adsorbed on ferrihydrite and goethite by the formation of an inner-sphere surface complex at pH 7.5. In the EXAFS spectra of the coprecipitated ferrihydrite and goethite, some features of the spectra significantly differed from those in the adsorbed samples. The EXAFS simulation indicated that the difference is due to the larger coordination number of the Fe atom to the Sb atom in the coprecipitation samples, indicating a structural incorporation (heterovalent substitution) of Sb(V) into ferrihydrite and goethite. The incorporation of Sb(V) into the structure was also confirmed in natural iron(III) oxyhydroxides in contaminated soil near an Sb mine tailing using mu-EXAFS. This study directly provided the first evidence for the structural incorporation of Sb(V) into the iron(III) oxide structure. Our findings are important for understanding the fate of Sb in the aquatic environment because the behavior of the elements incorporated into solids by such a substitution is not greatly influenced by aquatic factors such as the pH and ionic strength because of isolation of the incorporated metal(loid) ions from the aqueous phase.


Assuntos
Antimônio/química , Compostos de Ferro/química , Adsorção , Minerais
17.
Environ Sci Technol ; 44(4): 1281-7, 2010 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-20085342

RESUMO

The aim of this study was to determine the mechanism of Sb immobilization occurring under reductive soil conditions. In this work, we investigated the distribution and speciation of Sb in reductive soil formed in Sb mine tailing by micro-X-ray absorption near edge structure spectroscopy (micro-XANES) and electron probe microanalyzer (EPMA). EPMA and Fe K-edge micro-XANES analyses of the soil grains indicated that Sb in soil was strongly associated with Fe(III) hydroxides secondarily formed during sedimentation. The Sb concentrations in Sb hot-spot were found to be as high as 10-30 wt % (as Sb(2)O(5)). We also found quartz particles coated by secondary rims bearing Fe(III) hydroxides and Sb. The Sb K-edge micro-XANES analyses of the rims showed that a significant amount of Sb(III) was present only at the surfaces of the rims (thickness <10 microm), indicating that Sb reduction occurred in the reducing soil. The facts suggest that the reduction to Sb(III) in the system can be an important factor for Sb immobilization under reducing conditions, since the Sb(III) sorbs more strongly on Fe(III) hydroxides than Sb(V) and its solubility is also much lower than that of Sb(V) species.


Assuntos
Antimônio/análise , Antimônio/química , Mineração , Solo/análise , Monitoramento Ambiental , Oxirredução , Espectroscopia por Absorção de Raios X
18.
Environ Sci Technol ; 43(2): 318-23, 2009 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-19238958

RESUMO

Green rusts (GRs), which are mixed ferrous/ferric hydroxides, occur in many suboxic soils and sediments and are thought to play an important role in the fate and transport of many inorganic contaminants. In this study, the interaction of Sb with sulfate GR (GRSO4) was investigated using multitechnique approaches such as X-ray absorption fine structure (XAFS), XRD, and BET analyses. XANES analyses show that the oxidation states of Sb(V) sorbed on GRSO4 is dominantly Sb(V), suggesting that GRSO4 does not work as a strong reductant in the system of the present study. The sorption experiment EXAFS, and XRD results suggested that there are two bonding modes for Sb(V) sorption on GRSO4, (i) the sorption to edge sites with inner-sphere complex and (ii) to interlayer surface with outer-sphere complex. In addition, it was found that fraction (i) is dominant for Sb(V) sorption on GRSO4. The transformation of "metastable" GRSO4 was inhibited by the presence of Sb(V). The transformed products of GRSO4, such as magnetite and Fe(OH)2, have larger surface areas and higher capacities as adsorbent for Sb(V) than GRSO4, and the fraction of the transformed product largely affectsthe distribution of Sb between water and solid, a mixture of GRSO4, magnetite, and Fe(OH)2.


Assuntos
Antimônio/química , Compostos Férricos/química , Sulfatos/química , Adsorção , Antimônio/isolamento & purificação , Ferro , Soluções , Análise Espectral , Difração de Raios X
19.
Chemosphere ; 70(5): 942-7, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17761212

RESUMO

Green rust (Fe(4)(II)Fe(2)(III)(OH)(12)SO(4).3H(2)O) is an intermediate phase in the formation of iron (oxyhydr)oxides such as goethite, lepidocrocite, and magnetite. It is widely considered that green rust occurs in many soil and sediment systems. Green rust has been shown to reduce sorbed Se(VI), Cr(VI), and U(VI). In addition, it is also reported that green rust does not reduce As(V) to As(III). In this study, we have investigated for the first time the interaction between Sb(V) and green rust using XAFS and HPLC-ICP-MS. Most of the added Sb(V) was adsorbed on green rust, and Sb(III), a reduced form, was observed in both solid and liquid phases. Thus, it was shown that green rust has high affinity for Sb(V), and that Sb(V) was reduced to more toxic Sb(III) by green rust despite the high stability of the Sb(V) species even under reducing condition as reported in previous studies. Therefore, green rust can be one of the most important reducing agents for Sb(V), which can influence the Sb mobility in suboxic environments where green rust is formed.


Assuntos
Antimônio/química , Compostos Férricos/química , Compostos Ferrosos/química , Oxigênio/química , Poluentes do Solo/análise , Poluentes Químicos da Água/análise , Cromatografia Líquida de Alta Pressão , Clima , Óxido Ferroso-Férrico/química , Compostos de Ferro/química , Cinética , Minerais , Modelos Teóricos , Oxirredução , Poluentes do Solo/química , Análise Espectral , Luz Solar , Poluentes Químicos da Água/química
20.
Environ Sci Technol ; 42(24): 9045-50, 2008 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-19174869

RESUMO

The oxidation state and coordination environment of antimony (Sb) incorporated into polyethylene terephthalate (PET) bottles were estimated based on X-ray absorption fine structure (XAFS) at Sb K-edge. Prior to XAFS analyses, Sb concentrations in 177 PET bottles collected in Japan and China were determined, showing that 30.5% and 100% of Japanese and Chinese PET bottles, respectively, contained more than 10 mg/kg of Sb. Most of the bottles used for aseptic cold filling and carbonated drinks contained a larger amount of Sb. Extended X-ray absorption fine structure (EXAFS) showed that the first neighboring atom of Sb in PET was estimated to be oxygen with a coordination number of about three. In addition, the contribution of Sb to Sb shell was discounted in the EXAFS, showing that Sb was not present as Sb2O3 in PET, although Sb was initially added as Sb2O3 in the production of PET. This information is consistent with the coordination environment estimated from the polycondensation reaction catalyzed by Sb, where Sb can be present as either Sb glycolate or Sb glycolate binding to the end group of the PET polymer. X-ray absorption near-edge structure (XANES) showed that Sb(III) initially added as Sb2O3 into PET was partially oxidized and the Sb(V) fractions reached approximately 50% in some samples. However, the oxidation state and coordination environment of Sb in PET had no relationship with the concentrations of Sb that leached into water from PET. Based on the present XAFS results and previous studies on the effects of temperature and others, it was concluded that the leaching behavior of Sb into water is primarily due to the degradation of PET itself, but is not related to the Sb species in the PET bottles.


Assuntos
Antimônio/isolamento & purificação , Polietilenotereftalatos/química , Análise Espectral/métodos , China , Japão , Poluentes Químicos da Água
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