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Adsorption of Pb(2+), Cu(2+) and Cd(2+) in FDU-1 silica and FDU-1 silica modified with humic acid

Silva, Luis Carlos Cides da; SANTOS, L. B. O. dos; Abate, Gilberto; Cosentino, Ivana Conte; Fantini, Marcia Carvalho de Abreu; MASINI, J. C.; MATOS, J. R.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
608.03316%
Ordered mesoporous silica with cubic structure, type FDU-1, was synthesized under strong acid media using B-50-6600 poly(ethylene oxide)-poly(butilene oxide)-poly(ethylene oxide) triblock copolymer (EO(39)BO(47)EO(39)) and tetraethyl orthosilicate (TEOS). Humic acid (HA) was modified to the synthesis process at a concentration of 1.5 mmol per gram of SiO(2). Thermogravimetry, small angle X-ray diffraction, nitrogen adsorption and high resolution transmission electron microscopy were used to characterize the samples. The pristine FDU-1 and FDU-1 with incorporated 1.5 mmol of HA were tested for adsorption of Pb(2+), Cu(2+) and Cd(2+) in aqueous solution. Incorporation of humic acid into the FDU-1 silica afforded an adsorbent with strong affinity for Cd(2+), Cu(2+) and Pb(2+) from single ion solutions. Adsorption of Cu(2+) was significantly enhanced after incorporation of humic acid, a fact that can be explained by the formation of complexes with carboxylic and phenolic groups at low concentrations of the metal cation. The results demonstrated the potential applicability of FDU-1 with incorporated HA in the removal of low concentrations of heavy metal cations from aqueous solution, such as wastewaters, after usual precipitation of metal hydroxides in alkaline medium and proper pH conditioning in the range between 6 and 7. (C) 2007 Elsevier Inc. All rights reserved.

EVALUATION OF METAL TOXICITY BY A MODIFIED METHOD BASED ON THE FUNGUS GERRONEMA VIRIDILUCENS BIOLUMINESCENCE IN AGAR MEDIUM

MENDES, Luiz Fernando; STEVANI, Cassius Vinicius
Fonte: SETAC PRESS Publicador: SETAC PRESS
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
604.96727%
Metal cation toxicity to basidiomycete fungi is poorly understood, despite its well-known importance in terrestrial ecosystems. Moreover, there is no reported methodology for the routine evaluation of metal toxicity to basidiomycetes. In the present study, we describe the development of a procedure to assess the acute toxicity of metal cations (Na(+), K(+), Li(+), Ca(2+), Mg(2+), Co(2+), Zn(2+), Ni(2+), Mn(2+), Cd(2+), and Cu(2+)) to the bioluminescent basidiomycete fungus Gerronema viridilucens. The method is based on the decrease in the intensity of bioluminescence resulting from injuries sustained by the fungus mycelium exposed to either essential or nonessential metal toxicants. The assay described herein enables LIS to propose a metal toxicity series to Gerronenia viridilucens based on data obtained from the bioluminescence intensity (median effective concentration [EC50] values) versus metal concentration: Cd(2+) > Cu(2+) > Mn(2+) approximate to Ni(2+) approximate to Co(2+) > Zn(2+) > Mg(2+) > Li(+) > K(+) approximate to Na(+) > Ca(2+), and to shed some li-ht on the mechanism of toxic action of metal cations to basidiomycete fungi. Environ. Toxicol. Chem. 2010;29:320-326. (C) 2009 SETAC; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Fundacao de Amparo Pesquisa do Estado de Sao Paulo (FAPESP)[01/04753-6]; Fundacao de Amparo Pesquisa do Estado de Sao Paulo (FAPESP)[06/53628-3]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ceramic Crucible Corrosion by Heavy Metal Oxide Glasses, Part I: Phenomenological Study

Garcia dos Santos, Iêda Maria; Moreira, R. C M; De Souza, A. G.; Paskocimas, C. A.; Leite, E. R.; Varela, José Arana; Longo, Elson
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 198-205
ENG
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704.4789%
Heavy metal oxide (HMO) glasses have received special attention due to their optical, electrical and magnetic properties. The problem with these glasses is their corrosive nature. In this work, three ceramic crucibles (Al 2O 3, SnO 2 and ZrO 2) were tested in the melting of the system 40 PbO-35 BiO 1.5-25 GaO 1.5 (cation-%). After glass melting, crucibles were transversally cut and analyzed by scanning electronic microscopy (SEM), coupled to microanalysis by energy dispersive spectroscopy (EDS). Results indicated that zirconia crucibles presented the highest corrosion, probably due to its smallest grain size. Tin oxide crucibles presented a low corrosion with small penetration of the glass into the crucible. This way, these crucibles are an interesting alternative to melt corrosive glasses in instead of gold or platinum crucibles. It is important to emphasize the lower cost of tin oxide crucibles, compared to gold or platinum ones.

Bacterial activity in heavy metals polluted soils: Metal efflux systems in native rhizobial strains

Pereira, Paula Sá; Rodrigues, Mónica; Simões, F.; Domingues, Lucília; Castro, Isabel Videira e
Fonte: Taylor & Francis Publicador: Taylor & Francis
Tipo: Artigo de Revista Científica
Publicado em //2009 ENG
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508.1436%
The negative effect of high levels of heavy metals on the activity of soil microorganisms is well-known. However, some microorganisms survive even in high levels of heavy metals, and the microbial activity can therefore, help to recover these polluted soils. Microbial metal uptake in contaminated soils has to be tightly regulated to avoid toxic effects for the cells. These mechanisms of metal resistance are frequently associated to transport-related membrane proteins that mediate bacterium’s direct metabolic interactions with the complex soil and aquatic harsh environments. This study reports the identification of gene clusters in rhizobial strains that are regulated by heavy metals, particularly chromium. A DNA fragment was amplified from R. leguminosarum, and in silico analysis of the sequence obtained revealed a putative protein homologue to a cation/multidrug efflux pump component (GenBank DQ398937). Another amplified DNA fragment, with 960 bp, has strong homology with anion ABC transporters (GenBank ZP 002212691) and a peptide ABC transporter (Gen- Bank NP 766950), was identified in Mesorhizobium loti (GenBank DQ398941) and Sinorhizobium meliloti. Using ChromosomeWalking technique, a single product from Sinorhizobium meliloti was cloned and sequenced. This new fragment enlarged more 302 bp to the initial sequence corresponding to the ABC transporter...

The Role of Iron-Deficiency Stress Responses in Stimulating Heavy-Metal Transport in Plants1

Cohen, Clara K.; Fox, Tama C.; Garvin, David F.; Kochian, Leon V.
Fonte: American Society of Plant Physiologists Publicador: American Society of Plant Physiologists
Tipo: Artigo de Revista Científica
Publicado em /03/1998 EN
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499.06918%
Plant accumulation of Fe and other metals can be enhanced under Fe deficiency. We investigated the influence of Fe status on heavy-metal and divalent-cation uptake in roots of pea (Pisum sativum L. cv Sparkle) seedlings using Cd2+ uptake as a model system. Radiotracer techniques were used to quantify unidirectional 109Cd influx into roots of Fe-deficient and Fe-sufficient pea seedlings. The concentration-dependent kinetics for 109Cd influx were graphically complex and nonsaturating but could be resolved into a linear component and a saturable component exhibiting Michaelis-Menten kinetics. We demonstrated that the linear component was apoplastically bound Cd2+ remaining in the root cell wall after desorption, whereas the saturable component was transporter-mediated Cd2+ influx across the root-cell plasma membrane. The Cd2+ transport system in roots of both Fe-deficient and Fe-sufficient seedlings exhibited similar Michaelis constant values, 1.5 and 0.6 μm, respectively, for saturable Cd2+ influx, whereas the maximum initial velocity for Cd2+ uptake in Fe-deficient seedlings was nearly 7-fold higher than that in Fe-grown seedlings. Investigations into the mechanistic basis for this response demonstrated that Fe-deficiency-induced stimulation of the plasma membrane H+-ATPase did not play a role in the enhanced Cd2+ uptake. Expression studies with the Fe2+ transporter cloned from Arabidopsis...

CzcD Is a Heavy Metal Ion Transporter Involved in Regulation of Heavy Metal Resistance in Ralstonia sp. Strain CH34

Anton, Andreas; Große, Cornelia; Reißmann, Jana; Pribyl, Thomas; Nies, Dietrich H.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /11/1999 EN
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401.0567%
The Czc system of Ralstonia sp. strain CH34 mediates resistance to cobalt, zinc, and cadmium through ion efflux catalyzed by the CzcCB2A cation-proton antiporter. The CzcD protein is involved in the regulation of the Czc system. It is a membrane-bound protein with at least four transmembrane α-helices and is a member of a subfamily of the cation diffusion facilitator (CDF) protein family, which occurs in all three domains of life. The deletion of czcD in a Ralstonia sp. led to partially constitutive expression of the Czc system due to an increased transcription of the structural czcCBA genes, both in the absence and presence of inducers. The czcD deletion could be fully complemented in trans by CzcD and two other CDF proteins from Saccharomyces cerevisiae, ZRC1p and COT1p. All three proteins mediated a small but significant resistance to cobalt, zinc, and cadmium in Ralstonia, and this resistance was based on a reduced accumulation of the cations. Thus, CzcD appeared to repress the Czc system by an export of the inducing cations.

A Novel Histidine-Rich CPx-ATPase from the Filamentous Cyanobacterium Oscillatoria brevis Related to Multiple-Heavy-Metal Cotolerance

Tong, Liu; Nakashima, Susumu; Shibasaka, Mineo; Katsuhara, Maki; Kasamo, Kunihiro
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/2002 EN
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512.7915%
A novel gene related to heavy-metal transport was cloned and identified from the filamentous cyanobacterium Oscillatoria brevis. Sequence analysis of the gene (the Bxa1 gene) showed that its product possessed high homology with heavy-metal transport CPx-ATPases. The CPC motif, which is proposed to form putative cation transduction channel, was found in the sixth transmembrane helix. However, instead of the CXXC motif that is present in the N termini of most metal transport CPx-ATPases, Bxa1 contains a unique Cys-Cys (CC) sequence element and histidine-rich motifs as a putative metal binding site. Northern blotting and real-time quantitative reverse transcription-PCR showed that expression of Bxa1 mRNA was induced in vivo by both monovalent (Cu+ and Ag+) and divalent (Zn2+ and Cd2+) heavy-metal ions at similar levels. Experiments on heavy-metal tolerance in Escherichia coli with recombinant Bxa1 demonstrated that Bxa1 conferred resistance to both monovalent and divalent heavy metals. This is the first report of a CPx-ATPase responsive to both monovalent and divalent heavy metals.

A crystallographic study of the binding of 13 metal ions to two related RNA duplexes

Ennifar, Eric; Walter, Philippe; Dumas, Philippe
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Publicado em 15/05/2003 EN
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410.9693%
Metal ions, and magnesium in particular, are known to be involved in RNA folding by stabilizing secondary and tertiary structures, and, as cofactors, in RNA enzymatic activity. We have conducted a systematic crystallographic analysis of cation binding to the duplex form of the HIV-1 RNA dimerization initiation site for the subtype-A and -B natural sequences. Eleven ions (K+, Pb2+, Mn2+, Ba2+, Ca2+, Cd2+, Sr2+, Zn2+, Co2+, Au3+ and Pt4+) and two hexammines [Co (NH3)6]3+ and [Ru (NH3)6]3+ were found to bind to the DIS duplex structure. Although the two sequences are very similar, strong differences were found in their cation binding properties. Divalent cations bind almost exclusively, as Mg2+, at ‘Hoogsteen’ sites of guanine residues, with a cation-dependent affinity for each site. Notably, a given cation can have very different affinities for a priori equivalent sites within the same molecule. Surprisingly, none of the two hexammines used were able to efficiently replace hexahydrated magnesium. Instead, [Co (NH3)4]3+ was seen bound by inner-sphere coordination to the RNA. This raises some questions about the practical use of [Co (NH3)6]3+ as a [Mg (H2O)6]2+ mimetic. Also very unexpected was the binding of the small Au3+ cation exactly between the Watson–Crick sites of a G-C base pair after an obligatory deprotonation of N1 of the guanine base. This extensive study of metal ion binding using X-ray crystallography significantly enriches our knowledge on the binding of middleweight or heavy metal ions to RNA...

Influence of hydrostatic pressure on the effects of the heavy metal cations of manganese, copper, cobalt, and nickel on the growth of three deep-sea bacterial isolates.

Arcuri, E J; Ehrlich, H L
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1977 EN
Relevância na Pesquisa
624.7261%
Increases hydrostatic pressure varied the 72-h growth yield of three bacterial isolates from the deep sea in the presence of heavy metal cations of Mn, Cu, Co, and Ni, depending on the bacterial isolate, the metal cation and its concentration, and the level of hydrostatic pressure. Above atmospheric, hydrostatic pressure was found to have one of the following four effects on the response of culture growth to a heavy metal cation. (i) It could be without effect; (ii) it could enhance inhibition by a metal cation; (iii) it could increase the 72-h growth yield by a metal cation; or (iv) it could protect against a growth inhibitory effect noted at a lower pressure. Possible reasons for these varied responses are discussed.

The cobalt, zinc, and cadmium efflux system CzcABC from Alcaligenes eutrophus functions as a cation-proton antiporter in Escherichia coli.

Nies, D H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1995 EN
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414.49566%
The function of the CzcABC protein complex, which mediates resistance to Co2+, Zn2+, and Cd2+ in Alcaligenes eutrophus by cation efflux, was investigated by using everted membrane vesicles of Escherichia coli and an acridine orange fluorescence quenching assay. Since metal cation uptake could not be measured with inside-out membrane vesicles prepared from A. eutrophus and since available E. coli strains did not express the Czc-mediated resistance to cobalt, zinc, and cadmium salts, mutants of E. coli which exhibited a Czc-dependent increase in heavy metal resistance were isolated. E. coli mutant strain EC351 constitutively accumulated Co2+, Zn2+, and Cd2+. In the presence of Czc, net uptake of these heavy metal cations was reduced to the wild-type level. Inside-out vesicles prepared from E. coli EC351 cells displayed a Czc-dependent uptake of Co2+, Zn2+, and Cd2+ and a cation-triggered acridine orange fluorescence increase. The czc-encoded protein complex CzcABC was shown to be a zinc-proton antiporter.

P-Type ATPase Heavy Metal Transporters with Roles in Essential Zinc Homeostasis in Arabidopsis

Hussain, Dawar; Haydon, Michael J.; Wang, Yuwen; Wong, Edwin; Sherson, Sarah M.; Young, Jeff; Camakaris, James; Harper, Jeffrey F.; Cobbett, Christopher S.
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em /05/2004 EN
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601.72688%
Arabidopsis thaliana has eight genes encoding members of the type 1B heavy metal–transporting subfamily of the P-type ATPases. Three of these transporters, HMA2, HMA3, and HMA4, are closely related to each other and are most similar in sequence to the divalent heavy metal cation transporters of prokaryotes. To determine the function of these transporters in metal homeostasis, we have identified and characterized mutants affected in each. Whereas the individual mutants exhibited no apparent phenotype, hma2 hma4 double mutants had a nutritional deficiency phenotype that could be compensated for by increasing the level of Zn, but not Cu or Co, in the growth medium. Levels of Zn, but not other essential elements, in the shoot tissues of a hma2 hma4 double mutant and, to a lesser extent, of a hma4 single mutant were decreased compared with the wild type. Together, these observations indicate a primary role for HMA2 and HMA4 in essential Zn homeostasis. HMA2promoter- and HMA4promoter-reporter gene constructs provide evidence that HMA2 and HMA4 expression is predominantly in the vascular tissues of roots, stems, and leaves. In addition, expression of the genes in developing anthers was confirmed by RT-PCR and was consistent with a male-sterile phenotype in the double mutant. HMA2 appears to be localized to the plasma membrane...

The Chromosomally Encoded Cation Diffusion Facilitator Proteins DmeF and FieF from Wautersia metallidurans CH34 Are Transporters of Broad Metal Specificity

Munkelt, Doreen; Grass, Gregor; Nies, Dietrich H.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /12/2004 EN
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410.4161%
Genomic sequencing of the β-proteobacterium Wautersia (previously Ralstonia) metallidurans CH34 revealed the presence of three genes encoding proteins of the cation diffusion facilitator (CDF) family. One, CzcD, was previously found to be part of the high-level metal resistance system Czc that mediates the efflux of Co(II), Zn(II), and Cd(II) ions catalyzed by the CzcCBA cation-proton antiporter. The second CDF protein, FieF, is probably mainly a ferrous iron detoxifying protein but also mediated some resistance against other divalent metal cations such as Zn(II), Co(II), Cd(II), and Ni(II) in W. metallidurans or Escherichia coli. The third CDF protein, DmeF, showed the same substrate spectrum as FieF, but with different preferences. DmeF plays the central role in cobalt homeostasis in W. metallidurans, and a disruption of dmeF rendered the high-level metal cation resistance systems Czc and Cnr ineffective against Co(II). This is evidence for the periplasmic detoxification of substrates by RND transporters of the heavy metal efflux family subgroup.

Mitochondrial granules: are they reliable markers for heavy metal cations?

Brown, A C; Bullock, C G; Gilmore, R S; Wallace, W F; Watt, M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1985 EN
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499.06918%
Mitochondrial granules have been used as markers for heavy metal cations, but since such granules can also be found in tissues in the absence of such cations, an attempt was made to define conditions under which these different granules might be visualised. The tissue used was the smooth muscle of the central ear artery of the rabbit. In all studies, the presence or absence of mitochondrial granules was determined by several observers, using coded specimens so that the previous treatment of the specimens was not at the time known to the observers. Paired tissues were exposed for 30 or 90 minutes at 20, 30 or 39 degrees C to an incubate containing either 10 mmol/l barium or a control barium-free solution. After fixation in osmium tetroxide, there was no difference between the two groups; in both cases granules appeared more frequently the longer the time and the higher the temperature of incubation. In a further series where glutaraldehyde was the fixative, granules were identified in 23 out of 41 tissues incubated with barium, but in only 1 out of 41 control tissues (P less than 0.001). Electron probe microanalysis showed that granules in osmium-fixed tissues contained osmium as the main element, whereas granules in glutaraldehyde-fixed tissues which had been incubated with barium showed barium as the predominant cation. Thus mitochondrial granules can be reliable markers for heavy metal cations...

Heavy Metals in Soil and Crops of an Intensively Farmed Area: A Case Study in Yucheng City, Shandong Province, China

Jia, Lin; Wang, Wuyi; Li, Yonghua; Yang, Linsheng
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
408.70773%
Yucheng City is located in northwestern Shandong Province, China, and is situated on the Huang-Huai-Hai Plain, the largest alluvial plain in China. In this study, 86 surface soil samples were collected in Yucheng City and analyzed for cation exchange capacity (CEC), soil organic matter (SOM), pH, available phosphorus (avail. P), phosphorus (P), aluminum (Al), and iron (Fe). These soils were also analyzed for ‘total’ chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), mercury (Hg), cadmium (Cd), and lead (Pb), together with 92 wheat samples and 37 corn samples. There was no obvious heavy metal contamination in the soil and irrigation water. But the long-term accumulation of heavy metals in soil has lead to an increase of Ni, As, Hg and Pb concentrations in some of wheat and corn samples and Cd in wheat samples. Because of the numerous sources of soil heavy metals and the lower level of heavy metal in irrigation water, there is no significant relation between soil heavy metal concentrations and irrigation water concentrations. Cr, Ni were mainly from the indigenous clay minerals according to multivariate analysis. Little contribution to soil heavy metal contents from agricultural fertilizer use was found and the local anomalies of As...

Divalent Heavy Metal Cations Block the TRPV1 Ca2+ Channel

Pecze, László; Winter, Zoltán; Jósvay, Katalin; Ötvös, Ferenc; Kolozsi, Csongor; Vizler, Csaba; Budai, Dénes; Letoha, Tamás; Dombi, György; Szakonyi, Gerda; Oláh, Zoltán
Fonte: Humana Press Inc Publicador: Humana Press Inc
Tipo: Artigo de Revista Científica
EN
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490.27832%
Transient receptor potential vanilloid 1 (TRPV1) is a non-selective cation channel involved in pain sensation and in a wide range of non-pain-related physiological and pathological conditions. The aim of the present study was to explore the effects of selected heavy metal cations on the function of TRPV1. The cations ranked in the following sequence of pore-blocking activity: Co2+ [half-maximal inhibitory concentration (IC50) = 13 μM] > Cd2+ (IC50 = 38 μM) > Ni2+ (IC50 = 62 μM) > Cu2+ (IC50 = 200 μM). Zn2+ proved to be a weak (IC50 = 27 μM) and only partial inhibitor of the channel function, whereas Mg2+, Mn2+ and La3+ did not exhibit any substantial effect. Co2+, the most potent channel blocker, was able not only to compete with Ca2+ but also to pass with it through the open channel of TRPV1. In response to heat activation or vanilloid treatment, Co2+ accumulation was verified in TRPV1-transfected cell lines and in the TRPV1+ dorsal root ganglion neurons. The inhibitory effect was also demonstrated in vivo. Co2+ applied together with vanilloid agonists attenuated the nocifensive eye wipe response in mice. Different rat TRPV1 pore point mutants (Y627W, N628W, D646N and E651W) were created that can validate the binding site of previously used channel blockers in agonist-evoked 45Ca2+ influx assays in cells expressing TRPV1. The IC50 of Co2+ on these point mutants were determined to be reasonably comparable to those on the wild type...

Heavy Metal Concentrations in Soils and Factors Affecting Metal Uptake by Plants in the Vicinity of a Korean Cu-W Mine

Jung, Myung Chae
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 04/04/2008 EN
Relevância na Pesquisa
507.1986%
Heavy metal concentrations were measured in soils and plants in and around a copper-tungsten mine in southeast Korea to investigate the influence of past base metal mining on the surface environment. The results of chemical analysis indicate that the heavy metals in soils decreased with distance from the source, controlled mainly by water movement and topography. The metal concentrations measured in plant species generally decreased in the order; spring onions > soybean leaves > perilla leaves ≈ red pepper > corn grains ≈ jujube grains, although this pattern varied moderately between different elements. The results agree with other reports that metal concentrations in leaves are usually much higher than those in grain. Factors influencing the bioavailability of metals and their occurrences in crops were found as soil pH, cation exchange capacity, organic matter content, soil texture, and interaction among the target elements. It is concluded that total metal concentrations in soils are the main controls on their contents in plants. Soil pH was also an important factor. A stepwise linear multiple regression analysis was also conducted to identify the dominant factors influencing metal uptake by plants. Metal concentrations in plants were also estimated by computer-aided statistical methods.

A γ-Glutamyl Cyclotransferase Protects Arabidopsis Plants from Heavy Metal Toxicity by Recycling Glutamate to Maintain Glutathione Homeostasis[C][W]

Paulose, Bibin; Chhikara, Sudesh; Coomey, Joshua; Jung, Ha-il; Vatamaniuk, Olena; Dhankher, Om Parkash
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
490.27832%
This article identifies and characterizes an Arabidopsis protein, GGCT2;1, which has a cation transport regulator-like (ChaC-like) domain that functions as a γ-glutamyl cyclotransferase. In vivo studies in yeast and Arabidopsis establish that GGCT2;1 recycles Glu as part of the γ-glutamyl cycle and thus maintains GSH homeostasis to counteract heavy metal and metalloids toxicity.

Heavy metals in soils and crops in southeast Asia. 1. Peninsular Malaysia

Zarcinas, B.; Ishak, C.; McLaughlin, M.; Cozens, G.
Fonte: Kluwer Academic Publ Publicador: Kluwer Academic Publ
Tipo: Artigo de Revista Científica
Publicado em //2004 EN
Relevância na Pesquisa
486.50555%
In a reconnaissance soil geochemical and plant survey undertaken to study the heavy metal uptake by major food crops in Malaysia, 241 soils were analysed for cation exchange capacity (CEC), organic carbon (C), pH, electrical conductivity (EC) and available phosphorus (P) using appropriate procedures. These soils were also analysed for arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn) using aqua regia digestion, together with 180 plant samples using nitric acid digestion. Regression analysis between the edible plant part and aqua regia soluble soil As, Cd, Cr, Cu, Hg, Ni, Pb and Zn concentrations sampled throughout Peninsular Malaysia, indicated a positive relationship for Pb in all the plants sampled in the survey (R 2 = 0.195, p < 0.001), for Ni in corn (R 2 = 0.649, p < 0.005), for Cu in chilli (R 2 = 0.344, p < 0.010) and for Zn in chilli (R 2 = 0.501, p < 0.001). Principal component analysis of the soil data suggested that concentrations of Co, Ni, Pb and Zn were strongly correlated with concentrations of Al and Fe, which is suggestive of evidence of background variations due to changes in soil mineralogy. Thus the evidence for widespread contamination of soils by these elements through agricultural activities is not strong. Chromium was correlated with soil pH and EC...

Soil organic matter-metal interactions in Chilean volcanic soils under different agronomic management

Borie B., Gilda; Aguilera S., S. María; Peirano V., Pedro; Heredia, Wendy
Fonte: MARCEL DEKKER INC Publicador: MARCEL DEKKER INC
Tipo: Artículo de revista
EN
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402.48367%
The organic matter existing in volcanic soils must be investigated not only in quantity, but also in quality in order to understand its role in soils and thus ensure adequate levels of stable organic polymers contributing to soil humification. The meaningful contribution proposed by this investigation is based on the study of the interaction of soil organic matter (SOM) in its fractions humic acid and fulvic acid with metallic elements that are macro- and micronutrients and also contaminants. The study was carried out in Chilean soils of the type Andisols and Ultisols. To this end, humic acids and fulvic acids were fractionated to determine phenolic, carboxylic and total acidity. In addition cation holding capacity was determined. From the knowledge of this organic matter-metal interaction, the behavior and actual contribution of organic matter to soil may be inferred in relation to storage and availability of metallic elements, both nutrients and contaminants. The results of this study demonstrate the existence of electron-donor sites in the organic fractions of soil, which may be highly specific for heavy metals. They also confirm the possibility that metal-ion, especially micronutrient, bioavailability is affected by retention mechanisms involving the nature of SOM. Thus...

Preparation and characterisation of tamarind 4-hydroxybenzoic acid (THBA) resin and its use in extraction of heavy metal ions from industrial wastewater

Singh,AV; Kumawat,Indraj Kumar
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 EN
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508.5627%
The adsorption of heavy metal cations, Pb(II), Cd(II), Cu(II), Zn(II) and Fe(II) from aqueous solution by newly-synthesized tamarind 4-hydroxybenzoic acid (THBA) resin was investigated. The resin was characterised on the basis of FTIR, elemental analysis, ion-exchange capacity and physico-chemical properties. The distribution coefficients (Kd) and percentage adsorption of metal ions on resin were determined by batch methods using atomic absorption spectrophotometry (AAS). The effect of experimental parameters, such as pH, treatment time, temperature, adsorbent dose, initial metal ion concentration and flow rate, on the removal of metal ions was also studied. THBA resin proved to be an effective adsorbent for the removal of different heavy metal ions from aqueous solution; removal efficiency followed the order: Fe(II) > Cu(II) > Zn(II) > Cd(II) > Pb(II). These results suggest that the cation exchange resin THBA holds great potential to remove cationic heavy metal species from industrial wastewater.