Geochemistry of natural chromium occurrence in a sandstone aquifer in Bauru Basin, Sao Paulo State, Brazil

Anomalous concentrations of Cr(VI) occur in groundwaters of the Adamantina Aquifer, in a large region in the western state of Sao Paulo, sometimes exceeding the potability limit (0.05 mg L(-1)). To identify the possible geochemical reactions responsible for the occurrence of Cr in groundwater in Urania, borehole rock samples were collected in order to carry out mineralogical and chemical analyses. In addition, multilevel monitoring wells were installed and groundwater samples were analyzed. Analyses of the borehole rock samples show the occurrence of a geochemical anomaly of Cr in the quartzose sandstones (average concentrations of 221 ppm). Chrome-diopside is one of the main minerals contributing to this anomaly, having an average Cr content of 1505 ppm. Sequential extraction experiments indicated weakly adsorbed Cr in the order of 0.54 ppm, and this quantity is enough to provide the Cr concentrations observed in groundwater. Groundwaters from the monitoring wells proved to be stratified, with the highest concentrations of Cr(VI) (0.13 mg L(-1)) being associated with high redox and pH values (over 10) and high concentrations of Na. Geochemical reactions that may explain the release of Cr from the solid phase to groundwater involve the release of Cr(III) from minerals (like chrome-diopside and Cr-Fe hydroxide), followed by oxidation of Cr(III) to Cr(VI), probably related to the reduction of Mn oxides present in the aquifer. Then cation exchange occurs and dissolution of carbonates which increases the pH of groundwater, resulting in the desorption and mobilization of Cr(VI) into groundwater. (C) 2011 Elsevier Ltd. All rights reserved.

Lycopodiopsis derbyi Renault from the Corumbatai Formation in the state of Sao Paulo (Guadalupian of Parana Basin, Southern Brazil): New data from compressed silicified stems

Lycopodiopsis derbyi Renault was analyzed on the basis of compressed silicified stems from four Guadalupian outcrops of the Parana Basin (Corumbatai Formation) in the State of Sao Paulo, Southern Brazil. Dichotomous stems have been recorded, and three different branch regions related to apoxogenesis are described. The most proximal region has larger, clearly rhomboidal leaf cushions, with protruding upper edges; the intermediate transitional region also has rhombic leaf cushions, but they are smaller and less elongated than the lower in the same axis; finally, the most distal region reveals only incipient cushions, with inconspicuous infrafoliar bladders; interspersed microphylls were still attached. A well preserved branch representative of this most distal region was sectioned; it has a siphonostelic cylinder similar to that previously described for L derbyi. The cortex, however, shows new traits, such as a short portion of elongated cells between the periderm and the external cortex (or leaf cushion tissue). The stems were apparently silicified prior to their final burial but were probably not transported for long distances. Their final burial may have taken place during storm events, which were common during the deposition of the Corumbatai Formation. These stems are commonly deformed due to compression, mainly because the internal cortical portions rapidly decayed prior to silicification due to their thin-walled tissue, and are therefore not preserved. The common alkalinity of a shallow marine environment such as that in which the Corumbatai Formation was deposited, should mobilize the silica and favors petrifaction. Based on the new data, an emended diagnosis is proposed and a modification of the identification key published by Thomas and Meyen in 1984 for Upper Paleozoic Lycopsida is suggested. (C) 2009 Elsevier B.V. All rights reserved.

Chondrichthyans from the base of the Irati Formation (Early Permian, Parana Basin), Sao Paulo, Brazil

Three species of chondrichthyans are reported from conglomeratic sandstone at the base of the Lower Permian (Artinskian) Irati Formation (Parana Basin) near Rio Claro, Sao Paulo State, Brazil. The fossils include: 1) dispersed teeth of the petalodont ltapyrodus punctatus Silva Santos 1990, first described from the Permian (Artinskian) Pedra do Fogo Formation, Parnaiba Basin, Northeast Brazil; 2) a new species of tooth of the Order Orodontiformes; and 3) a new species of finspine of the Order Ctenacanthiformes. These fossils occur in an allochthonous assemblage of vertebrate remains including other Chondrichthyes, Xenacanthiformes and cladodonts, paleonisciform bony fish, and tetrapods. This discovery is a significant contribution to the sparse record of South American Chondrichthyes from the Early Permian and raises questions regarding the paleoenvironmental adaptations among these fish within Paleozoic basins of Brazil at this time. (C) 2010 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Anomalous content of chromium in a Cretaceous sandstone aquifer of the Bauru Basin, state of Sao Paulo, Brazil

Anomalous and natural concentrations of Cr(6+), occasionally exceeding the permitted limit for human consumption (0.05 mg/L), have been detected in groundwater in the northwestern region of the state of Sao Paulo. As part of a water-rock interaction investigation, this article describes the chemical and mineralogical characterization of rock samples taken from boreholes in the municipality of Urania, with the objective of identifying Cr-bearing minerals and determining how chromium is associated with these minerals. Rock sample analysis were performed using X-ray Fluorescence, X-ray Diffraction, Scanning Electron Microscopy, electron microprobe and sequential extraction techniques. Chemical analyses indicated that the quartzose sandstones show a geochemical anomaly of chromium, with an average content of 221 ppm, which is higher than the reported chromium content of generic sandstones (35 ppm). Diopside was identified as the primary Cr-bearing mineral potentially subject to weathering processes, with a chromium content of up to 1.2% as Cr(2)O(3). Many of the diopside grains showed dissolution features, confirming the occurrence of weathering. Sequential extraction experiments indicated that 99.3% of the chromium in samples is tightly bonded to minerals, whereas 0.24% is weakly bonded via adsorption. Assuming hypothetically that all adsorbed chromium is released via desorption, the theoretical Cr concentration in water would be one order of magnitude higher than the concentrations of Cr(6+) detected in groundwater. (C) 2010 Elsevier Ltd. All rights reserved.

The onset of flood basalt volcanism, Northern Parana Basin, Brazil: A precise U-Pb baddeleyite/zircon age for a Chapeco-type dacite

We report the first U-Pb baddeleyite/zircon date for a felsic volcanic rock from the Parana Large Igneous Province in south Brazil. The new date of 134.3 +/- 0.8 Ma for a hypocrystalline Chapeco-type dacite from Ourinhos (northern Parana basin) is an important regional time marker for the onset of flood basalt volcanism in the northern and western portion of the province. The dated dacite was erupted onto basement rocks and is overlain by a high-Ti basalt sequence, interpreted to be correlative with Pitanga basalts elsewhere. This new U-Pb date for the Ourinhos dacite is consistent with the local stratigraphy being slightly older than the few reliable step-heating (40)Ar/(39)Ar dates currently available for overlying high-Ti basalts (133.6-131.5 Ma). This indicates an similar to 3 Ma time span for the building of the voluminous high-Ti lava sequence of the Parana basin. On the other hand, it overlaps the (40)Ar/(39)Ar dates (134.8-134.1 Ma) available for the stratigraphically older low-Ti basalt (Gramado + Esmeralda types) and dacite-rhyolite (Palmas type) sequences from South Brazil, which is consistent with the short-lived character of this volcanism and its rapid succession by the high-Ti sequence. (C) 2010 Elsevier B.V. All rights reserved.

Precambrian geotectonic units of the Rio de La Plata craton

The main Precambrian tectonic units of Uruguay include the Piedra Alta tectonostratigraphic terrane (PATT) and Nico Perez tectonostratigraphic terrane (NPTT), separated by the Sarandi del Yi high-strain zone. Both terranes are well exposed in the Rio de La Plata craton (RPC). Although these tectonic units are geographically small, they record a wide span of geologic time. Therefore improved geological knowledge of this area provides a fuller understanding of the evolution of the core of South America. The PATT is constituted by low-to medium-grade metamorphic belts (ca. 2.1 Ga); its petrotectonic associations such as metavolcanic units, conglomerates, banded iron formations, and turbiditic deposits suggest a back-arc or a trench-basin setting. Also in the PATT, a late to post-orogenic, arc-related layered mafic complex (2.3-1.9 Ga), followed by A-type granites (2.08 Ga), and finally a taphrogenic mafic dike swarm (1.78 Ga) occur. The less thoroughly studied NPTT consists of Palaeoproterozoic high-grade metamorphic sequences (ca. 2.2 Ga), mylonites and postorogenic and rapakivi granites (1.75 Ga). The Brasiliano-Pan African orogeny affected this terrane. Neoproterozoic cover occurs in both tectonostratigraphic terranes, but is more developed in the NPTT. Over the past 15 years, new isotopic studies have improved our recognition of different tectonic events and associated processes, such as reactivation of shear zones and fluids circulation. Transamazonian and Statherian tectonic events were recognized in the RPC. Based on magmatism, deformation, basin development and metamorphism, we propose a scheme for the Precambrian tectonic evolution of Uruguay, which is summarized in the first Palaeoproterozoic tectonic map of the Rio de La Plata craton.

U-Pb zircon and (40)Ar-(39)Ar K-feldspar dating of syn-sedimentary volcanism of the Neoproterozoic Marica Formation: constraining the age of foreland basin inception and inversion in the Camaqua Basin of southern Brazil

New U-Pb zircon and (40)Ar-(39)Ar K-feldspar data are presented for syn-sedimentary volcanogenic rocks from the Neoproterozoic Marica Formation, located in the southern Brazilian shield. Seven (of nine) U-Pb sensitive high-resolution ion microprobe analyses of zircons from pyroclastic cobbles yield an age of 630.2 +/- 3.4 Ma (2 sigma), interpreted as the age of syn-sedimentary volcanism, and thus of the deposition itself. This result indicates that the Marica Formation was deposited during the main collisional phase (640-620 Ma) of the Brasiliano II orogenic system, probably as a forebulge or back-bulge, craton-derived foreland succession. Thus, this unit is possibly correlative of younger portions of the Porongos, Brusque, Passo Feio, Abapa (Itaiacoca) and Lavalleja (Fuente del Puma) metamorphic complexes. Well-defined, step-heating (40)Ar-(39)Ar K-feldspar plateau ages obtained from volcanogenic beds and pyroclastic cobbles of the lower and upper successions of the Marica Formation yielded 507.3 +/- 1.8 Ma and 506.7 +/- 1.4 Ma (2 sigma), respectively. These data are interpreted to reflect total isotopic resetting during deep burial and thermal effects related to magmatic events. Late Middle Cambrian cooling below ca. 200 degrees C, probably related to uplift, is tentatively associated with intraplate effects of the Rio Doce and/or Pampean orogenies (Brasiliano III system). In the southern Brazilian shield, these intraplate stresses are possibly related to the dominantly extensional opening of a rift or a pull-apart basin, where sedimentary rocks of the Camaqua Group (Santa Barbara and Guaritas Formations) accumulated.

Fuel ethanol price drivers in the Atlantic basin : Brazil & the U.S. traders perspectives

Como a oportunidade de exportação de etanol combustível é muito recente, o agronegócio carece de literatura para formação de gestores e estrategistas. Este trabalho tem como objetivo descrever o mecanismo de formação de preços de etanol tanto no Brasil como nos Estados Unidos da America. Decupei as variáveis que impactam na formação de preços, custo de produção de etanol de cana-de-açúcar, custo da logística e desidratação no Caribe, custo do etanol de milho e fiz algumas análises de cenários de formação de preços das principais variáveis e consegui organizar este conhecimento em um gráfico que contém no eixo superior preço do etanol hidratado na usina no Brasil e no eixo inferior o preço do bushel de milho em Chicago cujas interceções nas retas da taxa do dólar e do preço do gás natural, fornecem no eixo Y o preço do produto no porto de Nova York, ficando uma visualização simples das possibilidades da janela de exportação. A metodologia permite assumir diferentes cenários de oferta, demanda e preços e estabelecer diferentes estratégias de comercialização.

Reduction capability of soil humic substances from the Rio Negro basin, Brazil, towards Hg(II) studied by a multimethod approach and principal component analysis (PCA)

This paper characterizes humic substances (HS) extracted from soil samples collected in the Rio Negro basin in the state of Amazonas, Brazil, particularly investigating their reduction capabilities towards Hg(II) in order to elucidate potential mercury cycling/volatilization in this environment. For this reason, a multimethod approach was used, consisting of both instrumental methods (elemental analysis, EPR, solid-state NMR, FIA combined with cold-vapor AAS of Hg(0)) and statistical methods such as principal component analysis (PCA) and a central composite factorial planning method. The HS under study were divided into groups, complexing and reducing ones, owing to different distribution of their functionalities. The main functionalities (cor)related with reduction of Hg(II) were phenolic, carboxylic and amide groups, while the groups related with complexation of Hg(II) were ethers, hydroxyls, aldehydes and ketones. The HS extracted from floodable regions of the Rio Negro basin presented a greater capacity to retain (to complex, to adsorb physically and/or chemically) Hg(II), while nonfloodable regions showed a greater capacity to reduce Hg(II), indicating that HS extracted from different types of regions contribute in different ways to the biogeochemical mercury cycle in the basin of the mid-Rio Negro, AM, Brazil. (c) 2007 Published by Elsevier B.V.

Thermal Decomposition Kinetics of Humic Substances Extracted from Mid-Rio Negro (Amazon Basin) Soil Samples

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Distribution of Ra-226, Th-232 and K-40 in soils and sugar cane crops at Corumbatai river basin, São Paulo State, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Benthic foraminiferal distribution on the southeastern Brazilian shelf and upper slope

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

New species of Harttia (Loricariidae, Loricariinae) from the Rio Sao Francisco Basin

A new species of the mailed catfish genus Harttia is described from the Sao Francisco River drainage, States of Minas Gerais and Bahia, Brazil. The new species is distinguished from congeners by the combination of an abdominal region covered by small bony plates; plates 3-4 times in eye diameter; interorbital width 3.1-4.0 in head length and greater than eye diameter; body width at anal fin origin 6.3-8.3 in standard length; margins of the head and pectoral fin spine of mature males with elongate and conspicuous odontodes; anal fin of males longer than of females. A key to Harttia species and a comparison with other species are provided.

Changes in biomass, chemical composition and nutritive value of Spartina alterniflora due to organic pollution in the Itanhaém River Basin (SP, Brazil)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)