METALS IN SEDIMENTS FROM THE SHELF-SLOPE INTERFACE OFF THE POTIGUAR BASIN OFFSHORE OIL EXPLORATION AREA, NE BRAZIL. Marine sediments collected in November 2009 and July 2011 at depths ranging from 150 m to 2,000 m in the Potiguar Basin, northeastern Brazil, were analyzed for their main sedimentological characteristics (contents of carbon, nitrogen and their stable isotopes) and metals (Al, Fe, Mn, As, Cr, Cu, Ni, Pb, V and Zn) concentrations and their spatial distribution. Sediments were relatively rich in organic matter (C-org: 0.21% to 0.56%) and metals concentrations increased with depth, suggesting an accumulation of fine and terrigenous sediments eroded and transported from the continental shelf to the slope region. Metals concentrations were higher than those observed in coarser shelf sediments, because of sorting of fine-grained sediments. Iron (Fe), Cr and Cu distribution, although presenting this general pattern, also suggests some changes along the transport. Fe and Cr, probably in discrete minerals, are less affected by accumulation in deeper sediments. The high enrichment in Cu, however, suggests additional sources directly to slope sediments, probably by biological productivity and deposition through the water column. The concentrations of all metals are lower or fall close to the lowest range of concentrations reported for slope sediments from other marine regions worldwide and no evidence of anthropogenic contribution was evident.

Sepetiba Bay, Rio de Janeiro, Brazil, was home to a zinc smelter until its shutdown in 1998, and during 2011 the remains of the smelter were decommissioned. This study investigates the impact of decommissioning on metal concentrations in the bottom sediments of the bay. In addition to Zn and Cd, Cr, Cu, Ni and Pb are also quantified. The results show that over these 15 years, Cd and Zn concentrations have decreased by 100 and 70%, respectively. Temporal effects are also studied by applying five dated 210Pb cores, which are validated using the Zn and Cd profiles. The observed decrease in the Zn concentration in oysters is correlated with its reduction in the sediment. It was possible to verify the impact of Cr, Cu, Ni and Pb on the sediment quality due to the remaining metallurgical industries in the Sepetiba Bay basin.

Recentemente, a Associação Brasileira de Normas Técnicas (ABNT) lançou uma série de normas, relacionadas com a determinação de Na, K, Mg e Ca em biodiesel, recomendando procedimentos similares àqueles das normas europeias e americanas, mas também introduzindo uma norma alternativa (ABNT NBR 15556), que possibilita a determinação dos 4 elementos usando a técnica de espectrometria de absorção atômica com chama (F AAS). Neste trabalho, apresentam-se os estudos de otimização e validação que dão suporte a essa norma, bem como a comparação do desempenho de um equipamento com fonte de linhas com outro de fonte contínua. Entre os fatores otimizados, os baixos valores de taxa de aspiração e o uso de uma solução de óleo mineral em xileno para o ajuste da viscosidade entre soluções das amostras e de calibração devem ser destacados. Testes de precisão (repetitividade e precisão intermediária) mostraram valores adequados, comprovando a robustez do método, e os limites de detecção estiveram confortavelmente abaixo daqueles propugnados pelas legislações brasileira e internacional. A exatidão foi confirmada por testes de recuperação e pela participação em exercícios interlaboratoriais de proficiência promovidos pela Agência Nacional de Petróleo, Gás Natural e Biocombustíveis (ANP). A determinação dos 4 elementos por F AAS traz evidentes vantagens econômicas ao produtor, uma vez que se trata de um equipamento mais barato na sua aquisição e manutenção.

Recently, ABNT (Brazilian Association of Technical Standards) has presented a set of norms related to the determination of Na, K, Mg and Ca in biodiesel, recommending procedures similar to those of the European and American norms. However, it has also introduced an alternative norm (ABNT NBR 15556) wherein these 4 elements can be determined by flame atomic absorption spectrometry (F AAS). This work presents the studies that have supported this proposal and compares the performance of linear source equipment with a continuous source one in the application of the norm. Among the optimized factors, the low aspiration rate and the use of mineral oil solution in xylene to adjust the viscosity between samples and calibration solutions are highlighted. Precision tests (repeatability and intermediary precision) have shown adequate values, confirming the robustness of the method. Limits of detection were suitably below the legislation limits. The accuracy was confirmed by recovery tests as well as by the participation in interlaboratory proficiency tests promoted by the National Agency on Oil, Natural Gas and Biofuels (ANP, Brazil). The determination of these 4 elements by F AAS brings evident economic advantages to the producer, once F AAS is less expensive to purchase and maintenance.

Um procedimento de microdigestão para a determinação de Cd e Cu em amostras biológicas por espectrometria de absorção atômica em forno de grafite (GF AAS) é descrito. Massas de até 5 mg são pesadas diretamente na cubeta do amostrador automático e 100 µL de solução digestora (HNO3-H2SO4 1:1 v/v ou HNO3 concentrado) são adicionados. As cubetas são fechadas e a digestão é realizada a 60 ºC, por 12 h, em um bloco de digestão especialmente desenhado; seguem-se a adição de 900 µL de água ultrapura, a homogeneização e transferência das cubetas ao amostrador automático. O ambiente fechado e o uso de apenas um único frasco durante todo o processo minimizam os riscos de contaminação e perdas. Curvas analíticas externas, no mesmo meio do branco, mostraram-se adequadas para a calibração. A análise de nove diferentes materiais de referência certificados permitiu a avaliação da exatidão do procedimento. Os limites de quantificação na amostra original (5 mg), calculados a partir de dez sucessivas medições do branco (k = 10) foram 0,07 e 1,7 ou 0,02 e 0,3 µg g-1 para Cd e Cu, respectivamente, usando cada uma das misturas. O procedimento foi utilizado, com sucesso, para a determinação de Cu em amostras de biópsia de fígado humano.

A microdigestion procedure for the determination of Cd and Cu in biological samples by graphite furnace atomic absorption spectrometry (GF AAS) is described. Masses up to 5 mg are directly weighed in the autosampler cup and 100 µL of the digestion solution (1:1 v/v HNO3-H2SO4 or concentrated HNO3) are added. The cups are closed and the digestion is performed, at 60 ºC overnight in a specially designed digestion block. After cooling, 900 µL of ultrapure water is added, the solution is homogenized and the cups are transferred to the autosampler tray. Since the digestion is performed in a sealed environment and the whole procedure uses only one flask, the risks of contamination and losses are minimized. Calibration was performed with external calibration curves, in the same medium as the reagents blank. The analysis of nine different standard reference materials permitted the assessment to the accuracy of the procedure. Considering a 5 mg sample mass, the limits of quantification in the original samples calculated from ten successive measurements of the blank solution (k=10) were 0.07 and 1.7 and 0.02 and 0.3 µg g-1 for Cd and Cu respectively, using the HNO3-H2SO4 mixture or concentrated HNO3 for the digestion. The procedure was used for the determination of Cu in human liver biopsy samples.