RESUMO

Guanabara Bay, located in Rio de Janeiro state. It is surrounded by the second most important metropolitan area of the country. Over recent decades, land disturbance and urbanization in the surrounding area has significantly increased sediment input to the bay and had a negative effect on its overall environmental. This is especially related to high volumes of untreated sewage and industrial effluents. This study evaluates the history of this human impact through detailed examination of a sediment core taken from the northern portion of Guanabara Bay. A geochronology is established using ²¹°Pb dating and related to organic carbon and heavy metal fluxes to the sediments. This gave a calculated net average sedimentation rate for the core of 0.67 cm.year⁻¹. The organic carbon and heavy metals flux started to increase at the beginning of the last century and the highest values was observed in the top of the cores.

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RESUMO

In this study, the geochemical analysis of ten sediment samples collected along the fluvial system of the Estrela River, which flows into the northern portion of Guanabara Bay, shows the presence of anthropogenic impacts in this area. Concentrations of Fe, Mn, Zn, Cu, Pb, Cr and Ni obtained were slightly higher, when compared with values found in natural environments. The particle size and organic matter content in most of the analyzed stations showed features not conducive to the accumulation of pollutants due to the low organic matter content and the strong presence of sand fraction. There was also the fractionation of heavy metals in sediments and it was found the prominence of residual and reducible phase, besides the significant occurrence of organic fractions in some analyzed stations. These factors, thus, highlight the potential risks of contamination, where the metals associated with the organic phase can become bioavailable in processes of dissolution, provided by physico-chemical changes that can occur in this aquatic environment.

Assuntos

RESUMO

In this study, the geochemical analysis of ten sediment samples collected along the fluvial system of the Estrela River, which flows into the northern portion of Guanabara Bay, shows the presence of anthropogenic impacts in this area. Concentrations of Fe, Mn, Zn, Cu, Pb, Cr and Ni obtained were slightly higher, when compared with values found innatural environments. The particle size and organic matter content in most of the analyzed stations showed featuresnot conducive to the accumulation of pollutants due to the low organic matter content and the strong presence ofsand fraction. There was also the fractionation of heavy metals in sediments and it was found the prominence ofresidual and reducible phase, besides the significant occurrence of organic fractions in some analyzed stations. Thesefactors, thus, highlight the potential risks of contamination, where the metals associated with the organic phase canbecome bioavailable in processes of dissolution, provided by physico-chemical changes that can occur in this aquaticenvironment.

Neste estudo, analises geoquímicas de dez amostras de sedimentos coletadas ao longo do sistema fluvial do rio Estrela, que deságua na porção norte da Baía de Guanabara, evidenciam a presença de impactos antropogênicos nesta área. As concentrações de Fe, Mn, Zn, Cu, Pb, Cr e Ni obtidas foram ligeiramente elevadas, quando comparados com valores encontrados em ambientes naturais. A granulometria e o teor de matéria orgânica na maioria dos pontos analisados mostraram características não favoráveis à acumulação destes poluentes devido à baixa concentração de matéria orgânica e à forte presença de fração areia. Realizou-se também o fracionamento dos metais pesados nos sedimentos e constatou-se a preeminência da fase residual e redutível, além da ocorrência significativa da fração orgânica em alguns pontos analisados. Estes fatores evidenciam, portanto, riscos potenciais de contaminação, onde os metais associados à fase orgânica podem se tornar biodisponíveis em processos de solubilização, proporcionados por mudanças físico-químicas que podem ocorrer neste ambiente aquático.

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RESUMO

In this study, geochemical and particle size analyses of thirty-four street sediment samples collected from an urban environment around Guanabara Bay, shows highway run-off to be a potential source of heavy metals for the pollution of near-shore sedimentary deposits. Concentrations of Fe, Mn, Zn, Cu, Pb, Cr and Ni were found to be higher in these sediments when compared to concentrations found in samples from the natural environment, where an Enrichment Factor (EF) index was used to distinguish between natural and anthropogenic sources. Particle size analysis shows these sediments to be predominantly composed of sand and no distribution pattern was observed between the sand, silt and clay fractions. High levels of organic matter and heavy metals would indicate that these street run-off materials are a potential source of pollution for the near-shore sediments of Guanabara Bay.

Assuntos

RESUMO

In this study, geochemical and particle size analyses of thirty-four street sediment samples collected from an urban environment around Guanabara Bay, shows highway run-off to be a potential source of heavy metals for the pollution of near-shore sedimentary deposits. Concentrations of Fe, Mn, Zn, Cu, Pb, Cr and Ni were found to be higher in these sediments when compared to concentrations found in samples from the natural environment, where an Enrichment Factor (EF) index was used to distinguish between natural and anthropogenic sources. Particle size analysis shows these sediments to be predominantly composed of sand and no distribution pattern was observed between the sand, silt and clay fractions. High levels of organic matter and heavy metals would indicate that these street run-off materials are a potential source of pollution for the near-shore sediments of Guanabara Bay.

Neste estudo, análises geoquímica e de granulometria de trinta e quatro amostras de sedimentos coletados ao longo de rodovias em um ambiente urbano ao redor da Baía de Guanabara, mostram que o escoamento superficial das rodovias pode ser fonte potencial de metais pesados para a poluição de depósitos sedimentares costeiros. Concentrações de Fe, Mn, Zn, Cu, Pb, Cr e Ni são bem altas quando comparadas com os valores encontrados em ambientes naturais, onde o Fator de Enriquecimento (FE), que é índice de normalização, foi utilizado para a distinção entre fontes naturais e antropogênicas de metais pesados. As análises granulométricas mostram que estes sedimentos são compostos predominantemente de areia e nenhum padrão de distribuição foi observado entre as frações areia, silte e argila. Os altos níveis de matéria orgânica e metais pesados indicam que estes materiais depositados sobre as rodovias são fontes potenciais de poluição para os sedimentos costeiros da Baía de Guanabara.

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RESUMO

In order to evaluate environmental controls on the soiling formation and decay of building stones a set of mapping and physical and chemical analyses were carried out on granite from a historical church in the polluted centre of Rio de Janeiro. These techniques highlight the increasing of threatening damage on generally perceived as a durable building material, caused by granular disaggregation and contour scaling in areas close to ground level. Mapping also indicated the formation of black crusts over entire building façades, concentrated on areas sheltered from rain-wash. Analyses demonstrated the influence of marine aerosols, rock and mortar composition and mostly of the atmospheric pollutants on the decay and soiling of the granite. Much of the decay is associated specifically with the presence of halite (NaCl) and gypsum ((CaS04)2H2O). The fact that black, gypsum crusts are able to develop over entire façades in a humid subtropical environment is testimony to the high levels of local pollution, especially particulate deposition. Reduced rainwash, in sheltered micro-environments of narrow, canyon-like streets, overcomes the gypsum tendency to be washed away from buildings façades. These observations further highlight that decay processes are primarily controlled by microclimatic conditions.

RESUMO

As urbanisation accelerates within less-economically developed countries, populations in cities such as Rio de Janeiro are subject to numerous health risks relating to "heavy metal", sewage and vehicle pollution. These risks apply especially to children, through inhalation and dermal contact with pollutant-rich street sediments that reflect contamination from atmospheric deposition and act as effective sinks for heavy metals and oxalates. To assess the nature and extent of these risks street sediments were collected from industrial, commercial, residential and recreational areas with varying traffic densities within Rio de Janeiro. A modified selective extraction procedure was used to study the geochemical partitioning and bioavailability of Fe, Mn, Zn, Cu, Cr, Ni, Pb and C(2)O(4) (-). Oxalate partitioning has not been studied by traditional sequential methods and results from this procedure highlight the potential bioavailability of both oxalates and "heavy metals", especially Pb and C(2)O(4) (-) in industrial and recreational areas.

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