Atividade enzimática em lodo de esgoto contaminado com cádmio e uso em solo cultivado com sorgo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desorption of heavy metals from ion exchange resin with water and carbon dioxide

Adsorption and regeneration of ion exchange resins were studied using a subcritical solution of a CO₂-H₂O mixture and a fixed bed column. The commercial Amberlite IRC-50/IRC-86 cation exchange resins and Amberlite IRA-67 anion exchange resin were tested for heavy metals (Pb, Cu, Cd) adsorption from a solution with different initial metal concentrations at different temperatures. After adsorption, the loaded resins were regenerated with water and carbon dioxide at different temperatures and a pressure of 25 MPa. The efficiency of the IRC-50 resin was lower than that of the IRC-86 resin for the adsorption of metals like Cd, Cu and Pb. Results obtained for desorption of these metals indicated that the process could be used for Cd and in principle for Cu. Sorption of metal ions depended strongly on feed concentration. Mathematical modeling of the metal desorption process was carried out successfully as an extraction process. For this purpose, the VTII Model, which is applied to extraction from solids using supercritical solvents, was used in this work.

Metal ions bound to the human milk immunoglobulin A: Metalloproteomic approach

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Heavy metals and TPH effects on microbial abundance and diversity in two estuarine areas of the southern-central coast of São Paulo State, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Metals and semi-metals in street soils of So Paulo city, Brazil

So Paulo is the largest city in Brazil and South America with about 20 million inhabitants in the metropolitan area, more than nine million motor vehicles and intense industrial activity, which are responsible for increasing pollution in the region. Nevertheless, little is known concerning metal and semi-metal content in the soils of this metropolitan region. This type of information could be extremely useful as a fingerprint of environmental pollution. The present study determined the elements As, Ba, Co, Cr, Sb, and Zn concentrations in soils adjacent to avenues of highly dense traffic in So Paulo city to assess their levels and possible sources. The analytical technique employed was Instrumental neutron activation analysis. The results showed, except for Co, concentration levels higher than the reference values for soils of So Paulo, according to the Environmental Protection Agency of the State of So Paulo guidelines. When compared to similar studies in other cities around the world, So Paulo soils presented higher levels, probably due to its high density traffic and industrial activity. The concentrations obtained for As and Cr indicate anthropogenic origin. The high levels of the traffic-related elements Ba, Sb, and Zn in soils nearby high density traffic avenues indicate they may originate from vehicular exhausts.

Coffee is highly tolerant to cadmium, nickel and zinc: Plant and soil nutritional status, metal distribution and bean yield

Sewage sludge has been used to fertilize coffee, increasing the risk of metal contamination in this crop. The aim of this work was to study the effects of Cd, Zn and Ni in adult coffee plants growing under field conditions. Seven-year-old coffee plants growing in the field received one of three;loses of Cd, Zn or Ni: 15,45 and 90 g Cd plant(-1); 35, 105 and 210 g Ni plant(-1); and 100, 300 and 600 g Zn plant(-1), with all three metals in the form of sulphate salts. After three months, we noticed good penetration of the three metals into the soil, especially in the first 50 cm, which is the region where most coffee plant roots are concentrated. Leaf concentrations of K, Ca, Mg, S, B, Cu, Fe and Mn were nor affected. N levels did not change with the application of Ni or Zn but were reduced with either 45 or 90 g Cd plant(-1). Foliar P concentrations decreased with the addition of 45 and 90 g Cd plant(-1) and 600 g Zn plant(-1). Zn levels in leaves were not affected by the application of Cd or Ni. The highest concentrations. of Zn were found in branches (30-230 mg kg(-1)), leaves (7-35 mg kg(-1)) and beam (4-6.5 mg kg(-1)); Ni was found in leaves (4-45 mg kg(-1)), branches (3-18 mg kg(-1)) and beans (1-5 mg kg(-1)); and Cd was found in branches (0-6.2 mg kg(-1)) and beans (0-1.5 mg kg(-1)) but was absent in leaves. The mean yield of two harvests was not affected by Ni, but it decreased at the highest dose of Zn (600 g plant(-1)) and the two higher doses of Cd (45 and 90 g plant(-1)). Plants died when treated with the highest dose of Cd and showed symptoms of toxicity with the highest dose of Zn. Nevertheless, based on the amounts of metal used and the results obtained, we conclude that coffee plants are highly tolerant to the three metals tested. Moreover, even at high doses, there was very little transport to the beans, which is the part consumed by humans. (C) 2011 Elsevier B.V. All rights reserved.

Mechanistic changes observed in heavy water for nitrate reduction reaction on palladium-modified Pt(hkl) electrodes

Reduction of nitrate on palladium-modified platinum single-crystal electrodes has been investigated both voltammetrically and spectroscopically in acidic media (pH = 1). Results obtained in H2O and D2O solvents are compared for the three crystallographic orientations. FTIR and differential electrochemical mass spectrometry (DEMS) results clearly indicate that the isotopic substitution of the solvent has a large effect in the mechanism of the reaction, changing the nature of the detected products. For Pt(111)/Pd and Pt(100)/Pd, N2O is detected as the main product of nitrate reduction when D2O is used as solvent, while no N2O is detected when the reaction is performed in H2O. For Pt(110)/Pd, N2O is detected in both solvents, although the use of D2O clearly favours the preferential formation of this product. The magnitude of voltammetric currents is also affected by the nature of the solvent. This has been analysed considering, in addition to the different product distribution, the existence of different transport numbers and optical constants of the solvent.

Origin of the heavy elements in HD 140283 Measurement of europium abundance

Context. HD 140283 is a nearby (V = 7.7) subgiant metal-poor star, extensively analysed in the literature. Although many spectra have been obtained for this star, none showed a signal-to-noise (S/N) ratio high enough to enable a very accurate derivation of abundances from weak lines. Aims. The detection of europium proves that the neutron-capture elements in this star originate in the r-process, and not in the s-process, as recently claimed in the literature. Methods. Based on the OSMARCS 1D LTE atmospheric model and with a consistent approach based on the spectrum synthesis code Turbospectrum, we measured the europium lines at 4129 angstrom and 4205 angstrom, taking into account the hyperfine structure of the transitions. The spectrum, obtained with a long exposure time of seven hours at the Canada-France-Hawaii Telescope (CFHT), has a resolving power of 81 000 and a S/N ratio of 800 at 4100 angstrom. Results. We were able to determine the abundance A(Eu) = -2.35 +/- 0.07 dex, compatible with the value predicted for the europium from the r-process. The abundance ratio [Eu/Ba] = +0.58 +/- 0.15 dex agrees with the trend observed in metal-poor stars and is also compatible with a strong r-process contribution to the origin of the neutron-capture elements in HD 140283.

Metal biosorption onto dry biomass of Arthrospira (Spirulina) platensis and Chlorella vulgaris: Multi-metal systems

Binary and ternary systems of Ni2+, Zn2+, and Pb2+ were investigated at initial metal concentrations of 0.5, 1.0 and 2.0 mM as competitive adsorbates using Arthrospira platensis and Chlorella vulgaris as biosorbents. The experimental results were evaluated in terms of equilibrium sorption capacity and metal removal efficiency and fitted to the multi-component Langmuir and Freundlich isotherms. The pseudo second order model of Ho and McKay described well the adsorption kinetics, and the FT-IR spectroscopy confirmed metal binding to both biomasses. Ni2+ and Zn2+ interference on Pb2+ sorption was lower than the contrary, likely due to biosorbent preference to Pb. In general, the higher the total initial metal concentration, the lower the adsorption capacity. The results of this study demonstrated that dry biomass of C. vulgaris behaved as better biosorbent than A. platensis and suggest its use as an effective alternative sorbent for metal removal from wastewater. (C) 2012 Elsevier B.V. All rights reserved.

Availability of heavy metals in contaminated soil evidenced by chemical extractants

Heavy metals have been accumulating in Brazilian soils, due to natural processes, such as atmospheric deposition, or human industrial activities. For certain heavy metals, when in high concentrations in the soil, there is no specific extractant to determine the availability of these elements in the soil. The objective of the present study was to evaluate the availability of Cd, Cu, Fe, Mn, Pb and Zn for rice and soybeans, using different chemical extractants. In this study we used seven soil samples with different levels of contamination, in completely randomized experimental design with four replications. We determined the available concentrations of Cd, Cu, Fe, Mn, Pb and Zn extracted by Mehlich-1, HCl 0.1 mol L-1, DTPA, and organic acid extractants and the contents in rice and soybeans, which extracts were analyzed by ICP-OES. It was observed that Mehlich-1, HCl 0.1 mol L-1 and DTPA extractants were effective to assess the availability of Cd, Cu, Pb and Zn for rice and soybeans. However, the same was not observed for the organic acid extractant.

Origin of the heavy elements in HD 140283: measurement of europium abundance

Context. HD140283 is a nearby (V = 7:7) subgiant metal-poor star, extensively analysed in the literature. Although many spectra have been obtained for this star, none showed a signal-to-noise (S/N) ratio high enough to enable a very accurate derivation of abundances from weak lines. Aims. The detection of europium proves that the neutron-capture elements in this star originate in the r-process, and not in the s-process, as recently claimed in the literature. Methods. Based on the OSMARCS 1D LTE atmospheric model and with a consistent approach based on the spectrum synthesis code Turbospectrum, we measured the europium lines at 4129 Å and 4205 Å, taking into account the hyperfine structure of the transitions. The spectrum, obtained with a long exposure time of seven hours at the Canada-France-Hawaii Telescope (CFHT), has a resolving power of 81 000 and a S/N ratio of 800 at 4100 Å. Results. We were able to determine the abundance A(Eu) =

New functionalized ligands for luminescent metal complexes: from design to applications

The synthesis of luminescent metal complexes is a very challenging task since they can be regarded as the starting point for a lot of different areas. Luminescent complexes, in fact, can be used for technological, industrial, medical and biological applications. During my PhD I worked with different metals having distinguishing intrinsic properties that make them different from each other and, in particular, more or less suitable for the different possible uses. Iridium complexes show the best photophysical properties: they have high quantum yields, very long lifetimes and possess easily tunable emissions throughout the visible range. On the other hand, Iridium is very expensive and scarcely available. The aim of my work concerning this metal was, therefore, to synthesize ligands able not only to form luminescent complexes, but also able to add functionalities to the final complex, increasing its properties, and therefore its possible practical uses. Since Re(I) derivatives have been reported to be suitable as probes in biological system, and the use of Re(I) reduces the costs, the synthesized bifunctional ligands containing a pyridine-triazole and a biotin unit were employed to obtain new Re(I) luminescent probes. Part of my work involved the design and synthesis of new ligands able to form stable complexes with Eu(III) and Ce(III) salts, in order to obtain an emission in the range of visible light: these two metals are quite cheap and relatively non-toxic compared to other heavy metals. Finally, I plan to synthesize organic derivatives that already possessed an emission thanks to the presence of other many chromophoric groups and can be able to link the Zinc (II), a low cost and especially non-toxic “green” metal. Zinc has not its own emission, but when it sticks to ligands, it increases their photophysical properties.

Thermal release rate studies of nuclear reaction products from polycrystalline metal matrices

The thermal release rate of nuclear reaction products was investigated in offline annealing experiments. This work was motivated by the search for a high melting catcher material for recoiling products from heavy ion induced nuclear fusion reactions. Polycrystalline refractory metal foils of Ni, Y, Zr, Nb, Mo, Hf, W, and Re were investigated as catcher metals. Diffusion data for various tracer/host combinations were deduced from the measured release rates. This work focuses on the diffusion and the release rate of volatile p-elements from row 5 and 6 of the periodic table as lighter homologues of the superheavy elements with Z ≥ 113 to be studied in future experiments. A massive radiation damage enhancement of the diffusion velocity was observed. Diffusion trends have been established along the groups and rows of the periodic table based on the dependence of diffusion velocity on atomic sizes.

Pb pollution from leaded gasoline in South America in the context of a 2000-year metallurgical history

Exploitation of the extensive polymetallic deposits of the Andean Altiplano in South America since precolonial times has caused substantial emissions of neurotoxic lead (Pb) into the atmosphere; however, its historical significance compared to recent Pb pollution from leaded gasoline is not yet resolved. We present a comprehensive Pb emission history for the last two millennia for South America, based on a continuous, high-resolution, ice core record from Illimani glacier. Illimani is the highest mountain of the eastern Bolivian Andes and is located at the northeastern margin of the Andean Altiplano. The ice core Pb deposition history revealed enhanced Pb enrichment factors (EFs) due to metallurgical processing for silver production during periods of the Tiwanaku/Wari culture (AD 450–950), the Inca empires (AD 1450–1532), colonial times (AD 1532–1900), and tin production at the beginning of the 20th century. After the 1960s, Pb EFs increased by a factor of 3 compared to the emission level from metal production, which we attribute to gasoline-related Pb emissions. Our results show that anthropogenic Pb pollution levels from road traffic in South America exceed those of any historical metallurgy in the last two millennia, even in regions with exceptional high local metallurgical activity.

Human DNA ligase and DNA polymerase as molecular targets for heavy metals and anticancer drugs

DNA ligase and DNA polymerase play important roles in DNA replication, repair, and recombination. Frequencies of spontaneous and chemical- and physical-induced mutations are correlated to the fidelity of DNA replication. This dissertation elucidates the mechanisms of the DNA ligation reaction by DNA ligases and demonstrates that human DNA ligase I and DNA polymerase $\alpha$ are the molecular targets for two metal ions, Zn$\sp{2+}$ and Cd$\sp{2+},$ and an anticancer drug, F-ara-ATP.^ Human DNA ligases were purified to homogeneity and their AMP binding domains were mapped. Although their AMP-binding domains are similar, there could be difference between the two ligases in their DNA binding domains.^ The formation of the AMP-DNA intermediate and the successive ligation reaction by human DNA ligases were analyzed. Both reactions showed their substrate specificity for ligases I and II, required Mg2+, and were inhibited by ATP.^ A protein inhibitor from HeLa cells and specific for human DNA ligase I but not ligase II and T4 ligase was discovered. It reversibly inhibited DNA ligation activity but not the AMP-binding activity due to the formation of a reversible ligase I-inhibitor complex.^ F-ara-ATP inhibited human DNA ligase I activity by competing with ATP for the AMP-binding site of DNA ligase I, forming a ligase I-F-ara-AMP complex, as well as when it was incorporated at 3$\sp\prime$-terminus of DNA nick by DNA polymerase $\alpha.$^ All steps of the DNA ligation reaction were inhibited by Zn$\sp{2+}$ and Cd$\sp{2+}$ in a concentration-dependent manner. Both ions did not show the ability to change the fidelity of DNA ligation reaction catalyzed by human DNA ligase I. However, Zn$\sp{2+}$ and Cd$\sp{2+}$ showed their contradictory effects on the fidelity of the reaction by human DNA polymerase $\alpha.$ Zn$\sp{2+}$ decreased the frequency of misinsertion but less affected that of mispair extension. On the contrary, Cd$\sp{2+}$ increased the frequencies of both misinsertion and mispair extension at very low concentration. Our data provided strong evidence in the molecular mechanisms for the mutagenicity of zinc and cadmium, and were comparable with the results previously reported. ^