935 resultados para Foz do Amazonas Basin


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Total (HgT), reactive (HgR) and organic (Hg ORG) mercury species have been quantified in non-filtered waters collected from the Negro River Basin, Amazon (from January/2002 through January/2004), in both black and white water bodies. Black waters presented the highest HgT, HgORG and HgR concentration (29.1 ng L-1, 1.63 ng L-1 and 3.9 ng L-1, respectively), while, white waters presented the lowest HgT, Hg ORG and HgR concentration (8.8 ng L-1, 0.49 ng L-1 and 1.2 ng L-1, respectively). An inverse correlation between HgT and the water level over the basin was obtained, although the HgORG concentration has increased in the first rainy months and then decreased as the water level rose. Total mercury in surface sediments (0-10 cm) ranged from 70 to 271 mg kg-1 being the methylmercury 0.47-1.79 % of this stock. The results indicate that HgR and the labile dissolved organic matter were introduced into the aquatic environment during the flooding season, especially in the earlier stages, thus contributing to mercury methylation. ©2007 Sociedade Brasileira de Química.

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Oligosarcus perdido, a new species of freshwater fish from Serra da Bodoquena, upper Rio Paraguai basin, Brazil, is described. The new species is distinguished from congeners by the number of lateral-line scales, number of scales around the caudal peduncle, and osteological characters. The osteology of this new species is also documented by stereomicroscopic photography of cleared and stained specimens. Ecological notes based on direct observation by scuba diving in the field are also provided. Copyright © 2007 Magnolia Press.

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The waters of Corumbataí River in the middle and eastern part of São Paulo State, Brazil, are extensively used for human consumption; their water quality has been modified mainly due to increasing pressure caused by population growth, accompanied by a more accentuated industrial development for the whole São Paulo State in the early 1970s. The Corumbataí River basin has, over time, received significant emissions of municipal waste products and discharges of wastewater, sludge, sewage, sanitary and industrial effluents, but the first effluent treatment plant at Rio Claro city was only inaugurated at the end of the 1990s. Data on river water quality from two widely spaced locations in the Corumbataí River basin are reported in this paper; they indicate the need for continuous initiatives and efforts by decision makers in order to improve and preserve the water quality in the basin for the 21st century. Copyright © 2007 IAHS Press.

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Purpose: To determine the prevalence of trachoma in Sao Gabriel da Cachoeira (SGC), the only urban community of the upper Rio Negro Basin of the Amazon state in Brazil, near the Colombian border, and to investigate the risk factors associated with the active forms of the disease. Methods: A total of 1702 people (440 children up to 9 years and 1069 adults aged 15 years and above) were examined. The sample was selected from a probabilistic household sampling procedure based on census data and a previous study of trachoma prevalence in Sao Gabriel da Cachoeira. A two-stage probabilistic household cluster sample was drawn. Household units were randomly selected within each cluster. A variety of socioeconomic and hygiene variables were studied in order to determine the risk factors for active trachoma in a household. Results: The total prevalence of trachoma was 8.9%. Prevalence of active trachoma (TF and/or TI) in children aged 1-9 years was 11.1% and trachomatous trichiasis in adults aged 15 years and above was 0.19%. Trachomatous scarring reached a peak of 22.4% for subjects between 50 to 60 years of age. Corneal opacity occurred in subjects aged 50 years and older with a prevalence of 2.0%. No sex effect was found on the overall prevalence of trachoma in SGC. Risk factors associated with active trachoma were mainly related to poor socioeconomic indicators. Conclusions: Despite the ubiquitous presence of water, the analysis of the risk factors associated with the active forms of the disease supports the idea that a low personal standard of hygiene and not water availability per se, is the key factor associated with trachoma. Copyright © 2008 Informa Healthcare USA, Inc.

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The Triassic fish faunas of the Southern Hemisphere are only known from a few sedimentary basins and the most productive sites are those from the Karoo Supergroup, in South Africa and the Sydney Basin of Australia. A single lungfish tooth plate ascribed to Ptychoceratodus cf. philippsi was recovered from Late Triassic (Carnian) red beds of southern Brazil and is described herein. This find extends to South America the palaeogeographic distribution of the genus, which occurs in the Early Triassic of Australia and South Africa and the Middle/Late Triassic of Europe and Late Triassic of Madagascar and India. The presence of this dipnoan solely in the uppermost part of the Santa Maria Formation suggests that the migration of Ptychoceratodus towards the Paraná Basin began not before the late Induan/early Olenekian (late Early Triassic). At that time, more humid (monsoonal) conditions prevailed in what is now southern Brazil, compared to semi-arid/desert conditions that dominated the Late Permian and possibly the earliest Early Triassic (the latter presumably not represented in the Paraná Basin). © The Geological Society of London 2008.

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Calcareous Albian-Cenomanian strata in the Potiguar basin yield a number of microfossils, among which are calcareous algae (Dasycladales and Corallinales). This data, together with an inventory of previous discoveries, enabled the discussion of their biogeography. These benthic organisms probably came from the early Central Atlantic Ocean through its northwestern neck between Africa and South America and thus reached the early South Atlantic platforms.

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Includes bibliography

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During a recent inspection in the Paleontological Collection of the Institute of Geosciences, University of São Paulo, we have identifi ed some specimens of undescribed mollusk bivalves. These called our attention for the following reasons: a) all specimens are internal molds of conjugated and closed articulated valves, some of them presenting fragments of silicifi ed shells; b) all internal molds have similar general shape and internal characters, representing specimens of the same taxon; c) the internal molds and silicifi ed valves are well preserved, including fragile structures, which are hardly preserved, such as the internal mold of the external ligament and muscle scars; d) and equally important, according to the labels of all specimens, they were collected from rocks of the Passa Dois Group (Permian), Serrinha Member of the Rio do Rasto Formation. Although who collected the shells and the precise geographic location of the specimens are still unknown, the detailed study of these fossils brings us to the conclusion that they are morphologically distinct from any heretofore published genus of the endemic fauna of bivalves from Passa Dois Group. Based in its general shape, hinge structure and muscles scars, the new form can be classifi ed under the Family Megadesmidae Vokes, 1967, the most diverse group of Permian bivalves of the Paraná Basin. The specimens are referred as Beurlenella elongatella new gen. and sp. The shell shape and taphonomy indicate that this bivalve was a shallow, rapid, active burrower, suspension feeder, probably preserved in situ, in event deposits.

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In this study, the occurrence of Othonella araguaiana Mendes, a rare bivalve species is reported for the fi rst time in the Pinzonella illusa biozone, Middle Permian Corumbataí Formation, in the State of São Paulo. This species was originally described in coeval rocks of the Estrada Nova Formation (= Corumbataí) from the Alto Araguaia and Alto Garças regions, State of Mato Grosso. The specimens of O. araguaiana were found in the base of a bioclastic sandstone bed, a proximal tempestite, in the middle of the Corumbataí Formation, in the city of Rio Claro, São Paulo State. The silicifi ed shells and internal molds are well preserved, showing impressions of muscle scars and other internal anatomic characters (e.g., hinge), never illustrated by previous authors. In his original description, Mendes (1963) called attention to the similarity between O. araguaiana and Terraia aequilateralis, a common veneroid of the Corumbataí Formation. Conversely, Runnegar and Newell (1971) suggested that O. araguaiana belongs to Megadesmidae, being a junior synonym of Plesiocyprinella carinata (the commonest megadesmid of the Passa Dois Group). Our study indicates that O. araguaiana is indeed a megadesmid, but is distinct from the P. carinata. The new occurrence of O. araguaiana demonstrates that a) the paleobiogeographic distribution of this species is wider than previously thought (that it was restricted to the northern part of Paraná Basin, Mato Grosso State); b) the molluscan fauna of the Corumbataí Formation (P. illusa biozone) in the State of São Paulo is more diverse and dominated by megadesmids; and c) the composition of the molluscan fauna of the Corumbataí Formation in Alto Garças, State of Mato Grosso, is essentially the same as that of the P. illusa biozone of the eastern margin of the Paraná Basin.

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Incluye Bibliografía

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Includes bibliography

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Vascular plants were investigated in oxbow lakes of Turvo River, Upper Paraná River basin, between Icém and Nova Granada municipalities, state of São Paulo, Brazil. In this region, six lagoons were sampled: Ganzella, Mustafá, Braço Morto, 45, Federal, and Parente. The survey showed a total of 54 species, 36 genera and 22 families. The species richest families were Poaceae, Cyperaceae, and Polygonaceae. Eichhornia crassipes (Pontederiaceae) was the single species encountered in all the six lakes. © 2010 Check List and Authors.

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Includes bibliography