Coastal areas of passive margins are among the best places to examine the reality of sea-level changes. Elevation of marine terraces is central to interpretation of their approximate age in this kind of tectonic setting. The recognition of Pleistocene shorelines on the South American eastern continental margin is becoming increasingly common, but data are commonly imprecise in both time and space, and the resulting chronology is based mainly on geomorphological attributes. Nine thermoluminescence dates and four optically stimulated luminescence dates of 220^206 ka and 117^110 ka were obtained for two marine terrace deposits along 340 km of coast in Rio Grande do Norte State, northeastern Brazil. They are correlated with the highstands of marine oxygen-isotope substages 7c and 5c sea level, respectively. The older deposit occurs mainly on the N^S-trending coast and ranges in elevation between 7.5 and 1.3 m. The latter is found along the E^W-trending coast at altitudes that vary between 1 m and 20 m. It indicates relative downfaulting of the 220^206-ka marine terrace and uplift of the 117^110-ka marine deposit, which is locally about 12 m higher than deposits of similar age described 1000 km to the south. It follows that elevation alone is an unreliable tool for establishing a Quaternary sea-level change chronology also on passive margin coastal areas.

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The Cananéia (Upper Pleistocene) and the Comprida Island (Holocene) formations, outcropping in the Comprida island (SP) have been mapped using geomorphological and lithological criteria. Only one sample of the Cananéia Formation, collected in the homonymous island in front of the Comprida Island, was beyond the limit of the standard radiocarbon method. But since the publication of the geological map of the area in 1978, there has been some doubt on the real occurrence of Pleistocene deposits in southern extremity of Comprida Island. This paper deals with the results of thermoluminescence (TL) ages of eight samples from Comprida Island, which corroborate the Pleistocene age assumed during mapping surveys of these deposits. On the other hand, possible interpretations of the obtained ages, in relation to their depositional environments and related northern hemisphere Quaternary glaciations, are presented.

Recebido em 5/7/99; aceito em 25/11/99 ADSORPTION OF ZINC AND CADMIUM ON PEAT COLUMNS. The aim of this work was to evaluate the adsorption conditions of zinc and cadmium ions from aqueous solutions using a comercially available peat from Balneário Arroio do Silva, Santa Catarina State, Brazil. Adsorption studies were carried out in column experiments using radiotracers of the studied metals ( 65 Zn and 115 Cd). The pH influence and the interference of other ions, such as Na + , Ca 2+ , Fe 3+ and Al 3+ on the adsorption process were investigated. The results showed that peat columns are able to retain more than 99% of metal ions in solution in a range of pH from 3,7 to 6,5. Ca 2+ and Al 3+ ions were the main interferent on adsorption of Zn and Cd ions in solution.Keywords: peat columns; adsorption; zinc and cadmium. ARTIGO INTRODUÇÃOA turfa é um sedimento orgânico recente, formado a partir da decomposição parcial da matéria vegetal em um ambiente úmido, ácido e de pouca oxigenação. Sob o ponto de vista físico-químico, é um material poroso, altamente polar, com elevada capacidade de adsorção para metais de transição e moléculas orgânicas polares 1 . A forte atração da turfa pela maioria dos cátions metálicos em solução deve-se, principalmente, ao elevado teor de substâncias húmicas (ácidos húmico e fúlvico) na sua matéria orgânica. Essas substâncias, também conhecidas como polímeros naturais, são ricas em grupos funcionais com cargas negativas, tais como ácidos carboxílicos e hidroxilas fenólicas e alcoólicas, que são justamente os sítios de adsorção dos metais em solução. A Figura 1 apresenta um modelo da estrutura de uma molécula de ácido húmico, onde podem ser observados os grupos funcionais oxigenados distribuídos nos anéis aromáticos 2 .de baixo custo, aplicado ao tratamento de águas e efluentes contaminados por metais pesados e outras substâncias tóxicas 1 . No Brasil, esse material tem a sua aplicação voltada à agricultura 3 ou como material combustível, dado o seu elevado teor de carbono 4 . Entretanto, poucos trabalhos foram publicados referentes à utilização de turfas nacionais aplicadas ao tratamento de águas e efluentes contaminados 5,6 . Este trabalho tem como objetivo principal verificar as melhores condicões de retenção dos metais zinco e cádmio em colunas de turfas nacionais, visando a aplicação desse material em sistemas de tratamento de águas e efluentes contaminados por metais pesados, visto que o Brasil possui uma reserva estimada em 1,6 bilhões de metros cúbicos de material turfeiro distribuídos em mais de duzentas turfeiras ao longo do seu território 7 . Neste trabalho, inicialmente, a turfa foi caracterizada segundo técnicas apropriadas de análise de solos. Nos experimentos de adsorção foram estudadas as influências do pH e dos íons Na + , Ca 2+ , Fe 3+ e Al 3+ como interferentes no processo de retenção dos metais nas colunas. O critério de escolha dos interferentes foi baseado na ocorrência comum desses íons nas águas e efluentes, aparecendo geralmente como constituintes de sais inorgânicos...

Resumo A Formação Barreiras no nordeste do estado do Pará é recoberta discordantemente por uma variedade de estratos oxidados, de coloração vermelha clara a amarela pálida, cujas idades são apresentadas, pela primeira vez, no presente trabalho. Utilizando-se métodos de datação por luminescência opticamente estimulada (LOE), seguindo-se os protocolos MAR (Multiple Aliquot Regeneration) e SAR (Single Aliquot Regeneration) e, quando possível, 14 C, pode-se constatar que a formação desses estratos ocorreu no final do Pleistoceno tardio ao Holoceno, tendo-se registrado idades LOE/MAR entre 430.000 (±60.000) e 3.400 (±400) anos AP. A comparação dos resultados LOE/MAR e LOE/SAR mostrou boa equivalência dos valores nas idades mais jovens, e diferenças significativas para as idades relativamente mais antigas. O fato dos estratos com idades mais antigas mostrarem evidências de deposição sob condições subaquosas levou a concluir que as diferenças obtidas indicam, muito possivelmente, que os grãos analisados não foram zerados com respeito à radiação solar no momento da deposição, refletindo a radiação adquirida em sítios deposicionais anteriores a sua última deposição. Considerando-se as idades obtidas, e integrando-se informações oriundas de publicações anteriores, conclui-se que os Sedimentos Pós-Barreiras registram a margem de um amplo paleovale, cujo registro principal ocorre a oeste da área de estudo, onde estratos correlatos são melhor desenvolvidos. Palavras-chave:Quaternário, Sedimentos Pós-Barreiras, datação, luminescência opticamente estimulada, Ilha do Marajó. Abstract Dating Post-Barreiras Sediments in Northern Brazil: palaeogeographic implications.The Barreiras Formation exposed in the northeastern of the State of Pará, overlain by a variety of oxidized, light red to pale yellow strata, whose ages are presented, for the first time, in the present work. Based on dating methods applying optically stimulated luminescence (OSL) following the protocols MAR (Multiple Aliquot Regeneration) and SAR (Single Aliquot Regeneration) and, whenever possible, 14 C, it was possible to conclude that the formation of these strata took place at the end of late Pleistocene to Holocene, with recorded LOE/MAR ages ranging from 430,000 (±60,000) to 3,400 (±400) yr BP. A comparison of OSL/MAR and OSL/SAR results showed good equivalence among values for the deposits with younger ages, and significant differences for deposits with relatively older ages. The fact that strata with older ages show evidence for deposition under sub-aqueous conditions led to conclude that the differences obtained herein is more likely due to the cosmic radiation acquired during deposition in previous depositional sites. Taking into account the obtained ages, and integrating these data with information derived from previous publications, it can be concluded that the Post-Barreiras Sediments record deposition at the margin of a wide paleovalley, which display its main sedimentary record to the west of the study area.Keywords: Quaternary, Post-Barreiras Sediment...

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The literature presents many methods for partitioning of data set, and is difficult choose which is the most suitable, since the various combinations of methods based on different measures of dissimilarity can lead to different patterns of grouping and false interpretations. Nevertheless, little effort has been expended in evaluating these methods empirically using an archaeological data set. In this way, the objective of this work is make a comparative study of the different cluster analysis methods and identify which is the most appropriate. For this, the study was carried out using a data set of 45 samples of ceramic fragments, analyzed by instrumental neutron activation analysis (INAA). The methods used for this study were: Single linkage, Complete linkage, Average linkage, Centroid and Ward. The validation was done using the cophenetic correlation coefficient and comparing these values the average linkage method obtained better results. A script of the statistical program R with some functions was created to obtain the cophenetic correlation. By means of these values was possible to choose the most appropriate method to be used in the data set.

Adsorption of mercury(ll) and methylmercury by two tannin sorbents was investigated using radiotracers. High sorption capacities for mercury are registered for both sorbents at pH 7. For Eucaliptus Saligna Sm sorbent (ETS) the maximum sorption capacity was 1.2_+.0.2 mmol/g and for Lysiloma latisiliqua sorbent (LTS) was 8.5+0.2 mmol/g. Methylmercury adsorption maximum was recorded at pH 4 and in buffered solutions at pH2. This species can be recovered in the presence of mercury(ll). Influence of different ions present in water was examined. High recoveries were reported for ETS in tap water samples but a decrease of uptake is observed for seawater.