4 resultados para radioactive metal mercury dissoln extn tonic liq solvent perhalide
em Biblioteca Digital da Produção Intelectual da Universidade de São Paulo
Resumo:
Biomarkers as lipid peroxidation, metallothionein and delta-aminolevulinic acid dehydratase were determined in Cathorops spixii to compare the biological responses of this fish from estuaries with distinct anthropogenic influence. Three areas were selected in two estuaries in accordance with the levels of contamination for the polluted (Santos/So Vicente) and with the hydrodynamic characteristics for the non-polluted (Canan,ia) estuary. Water characteristics and mercury levels in C. spixii confirmed a high human influence in the polluted system. In general, the biomarkers showed differences between the estuaries, suggesting disturbances in the specific cell mechanisms due to the presence of multiple xenobiotics in the contaminated system. Therefore, these biomarkers are recommended to promote more accurate information about the exposure to pollutants. Additionally, the study of the effect of the multiple xenobiotics on resident species such as the benthic fish C. spixii can favor a better assessment of the environmental quality of these systems.
Resumo:
Twenty six bottom sediment samples were collected from the Cananeia estuary in summer and winter of 2005. Multielemental analysis was carried out by instrumental neutron activation analysis. Total mercury was determined by cold vapor atomic absorption. As, Cr, Hg and Zn concentrations were compared to the Canadian oriented values (TEL and PEL). Sample points 4 and 9 presented higher concentration for most elements and As and Cr exceeded the TEL values. Organic matter (>10%) associated with siltic and clay sediments was observed. Climatic conditions, hydrodynamic and biogeochemical processes promote differences in seasonal concentrations of elements at some points, which contribute to special distributions.
Resumo:
Sediments of the Lagoa Vermelha (Red Lake), situated in the Ribeira Valley, southeastern Brazil, are made of a homogeneous, organic-rich, black clay with no visible sedimentary structures. The inorganic geochemical record (Al, As, Ba, Br, Co,Cs, Cr, Fe, Mn, Ni, Rb, Sc, Sb, V, Zn, Hg and Pb) of the lake sediments was analyzed in a core spanning 2430 years. The largest temporal changes in trace metal contents occurred approximately within the last 180 years. Recent sediments were found to be enriched in Pb, Zn, Hg, Ni, Mn, Br and Sb (more than 2-fold increase with respect to the "natural background level"). The enhanced accumulation of Br, Sb, and Mn was attributed to biogeochemical processes and diagenesis. On the other hand, the anomalous concentrations of Pb, Zn, Hg and Ni were attributed to pollution. As Lagoa Vermelha is located in a relatively pristine area, far removed from direct contamination sources, the increased metal contents of surface sediments most likely resulted from atmospheric fallout. Stable Pb isotopes provided additional evidence for anthropogenic contamination. The shift of Pb-206/Pb-207 ratios toward decreasing values in the increasingly younger sediments is consistent with an increasing contribution of airborne anthropogenic lead. In the uppermost sediments (0-10 cm), the lowest values of the Pb-206/Pb-207 ratios may reflect the influence of the less radiogenic Pb from the Ribeira Valley District ores (Pb-206/Pb-207 between 1.04 and 1.10), emitted during the last 50 years. (C) 2011 Elsevier Ltd. All rights reserved.
Resumo:
We report on a new, promising nanotechnological approach for hydrometallurgy based on recyclable, chemically functionalized superparamagnetic nanoparticles. In this process, the metal ions (e.g. Cu2+) are captured by the nanoparticles and confined at the electrode surface by means of an external magnet. Due to the pre-concentration effect the electrodeposition process is greatly improved, yielding the pure metal in a much shorter time in comparison with the conventional electrodeposition process. After the electrolysis, the magnetic nanoparticles are ready to return to the process. The proposed strategy can advantageously be incorporated in hydrometallurgy, reducing the number of steps associated with complexation, organic solvent extraction, metal release and diffusional electroprocessing, leading to a more sustainable technology. (C) 2012 Elsevier B.V. All rights reserved.