Eutrofização e capacidade de carga de fósforo de seis reservatórios a bacia do Rio Seridó, região semi-árida do Estado do RN

The eutrofization is a natural process of accumulation of nutrients in aquatic´s body that it has been accelerated for the human´s actives, mainly the related with the activities of camp, industrial and the inadequate disposition of the domestic sewage. The enrichment of the aquatic´s body with nutrients, mainly the nitrogen and the phosphorus, and the consequent proliferation of algae and Cyanobacteria can commit the quality of the water for the public provisioning, for the fish farming and for other ends. The problem becomes more critical when there is a shortage of water naturally as in the semi-arid area of the Brazilian northeast. Before that problem this work had as objective evaluates the trophic state of six reservoirs of the basin of River Seridó of Rio Grande of Norte and also estimate the capacity of load of match of the reservoir and risk probabilities based on the established limits by the resolution Conama 357/05. The results demonstrate that the six reservoirs are eutrofization, with concentration of total phosphorus and cloro a in the water upster to 50 e 12 μg l-1. The results show that space homogeneity exists in the state trophic of the reservoirs, but a significant variation interanual in function of the increase of the concentrations of nutrients and decrease of the transparency of the water with the reduction of the body of water accumulated in the reservoirs.The results of the simulation risk estocastic show that the reservoirs could receive annually from 72 to 216 Kg of P, assuming a risk of 10% of increasing in more than 30 μg l-1 the annual medium concentrations of total match in the water of these reservoirs. This load could be high in until 360 kg of P a year in case the managers assume a risk of 10% of increasing in more than 50 μg l-1 the annual medium concentrations of total phosphorus in the waters of these reservoirs

Evolução diagenética e caracterização dos reservatórios da seção devoniana na Bacia do Rio do Peixe-Nordeste do Brasil

The Rio do Peixe Basin represents a main basin of northeastern Brazil and pioneering work positioned the rocks of this basin in the Early Cretaceous. However, a recent study, based on integrated pollen analysis from three wells, found an unprecedented siliciclastic sedimentary section, in the region, of early Devonian age. Therefore, the present study aims a detailed petrographic and petrological analysis of this devonian section, in the Rio do Peixe Basin and proposes a diagenetic evolution, to understand the characteristics of the porous system, identify the main reservoir petrofacies with the main factors impacting on the quality of these rocks as reservoirs and a quick study on the provenance of this section. The petrographic study was based on samples obtained from subsurface and surface. The diagenetic evolution of petrofacies and its identification were based only on subsurface samples and the study of provenance was based on surface samples. The thin sections were prepared from sandstones, pelites and sandstones intercalated with pelites. The original detrital composition for this section is arcosean and the main diagenetic processes that affected these rocks occur in various depths and different conditions, which resulted in extensive diagenetic variety. The following processes were identified: early fracture and healing of grains; albitization of K-feldspar and plagioclase; siderite; precipitation of silica and feldspar; mechanical infiltration of clay and its transformation to illite/esmectite and illite; autigenesis of analcime; dissolution; autigenesis of chlorite; dolomite/ferrous dolomite/anquerite; apatite; calcite; pyrite; titanium minerals and iron oxide-hidroxide. The occurrence of a recently discovered volcanism, in the Rio do Peixe Basin, may have influenced the diagenetic evolution of this section. Three diagenetic stages affected the Devonian section: eo, meso and telodiagenesis. This section is compositionally quite feldspathic, indicating provenance from continental blocks, between transitional continental and uplift of the basement. From this study, we observed a wide heterogeneity in the role of the studied sandstones as reservoirs. Seven petrofacies were identified, taking into account the main diagenetic constituent responsible for the reduction of porosity. It is possible that the loss of original porosity was influenced by intense diagenesis in these rocks, where the main constituent for the loss of porosity are clays minerals, oxides and carbonate cement (calcite and dolomite)

Nenneguya garavelli n. sp and Myxobolus peculiaris n. sp (Myxozoa : Myxobolidae) in the gills of Cyphocharax nagelli (Osteichthyes : Curimatidae) from Rio do Peixe Reservoir, Sao Jose do Rio Pardo, São Paulo, Brazil

The present work describes myxozoans found in Cyphocharax nagelli (Characiformes: Curimatinae) commonly called saguiru collected from Rio do Peixe Reservoir, Sao Jose do Rio Pardo, São Paulo, Brazil. From a total of 38 examined fish, 24 were infected with Henneguya garavelli n. sp. (63% prevalence) and two with Myxobolus peculiaris n. sp. (5% prevalence) in the gills. Spores were studied by staining and fresh spores were observed by differential interference contrast optics. Henneguya garavelli n. sp. differs from Henneguya iheringi , Henneguya occulta, Henneguya cesarpintoi, Henneguya santae, Henneguya pisciforme, Henneguya amazonica, Henneguya striolata, Henneguya leporinicola and Henneguya chydadea in spore length and from Henneguya travassosi, Henneguya adherens, Henneguya malabarica, Henneguya piaractus and also Henneguya chydadea in polar capsule length and tail length. Myxobolus peculiaris n. sp. was very different when compared to other species of Myxobolus in its morphology and the biggest size of spore body. The authors present tables with comparative measurements of Brazilian myxozoan parasites. (c) 2006 Elsevier B.V. All rights reserved.

Ecologia da ictiofauna de um córrego de cabeceira da bacia do alto rio Paraná, Brasil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação de características morfométricas na relação solo-superfície da Bacia Hidrográfica do Córrego Rico, Jaboticabal (SP)

Com a análise das características morfométricas procura-se entender a relação solo-superfície, em decorrência dos processos erosivos sobre estruturas e litologias variadas. Neste trabalho, objetivou-se avaliar as características morfométricas do padrão de drenagem e do relevo em microbacias hidrográficas de 2ª ordem de magnitude, em Latossolo Vermelho-Escuro e Argissolo Vermelho-Amarelo, com vistas ao planejamento agroambiental da Bacia Hidrográfica do Córrego Rico, município de Jaboticabal, SP. O estudo foi baseado em fotografias aéreas, pancromáticas, verticais na escala 1:35.000 da região administrativa de Ribeirão Preto. Com técnicas de fotointerpretação, foram traçadas a rede de drenagem e respectivas microbacias hidrográficas, onde as variáveis selecionadas foram determinadas. As classes de risco de degradação, resultando no uso potencial do solo, foram determinadas de acordo com o coeficiente de rugosidade. As características do padrão de drenagem e do relevo repercutiram no comportamento hidrológico e litológico das microbacias hidrográficas, possibilitando a diferenciação entre as unidades de solos. A densidade de drenagem e a amplitude altimétrica foram as características que mais contribuíram para o poder discriminatório na relação solo-superfície. Na análise conjunta do potencial de uso do solo, verificou-se, principalmente, adequação para agricultura nos Latossolos e pecuária e, ou, reflorestamento nos Argissolos.

Degradação ambiental da bacia hidrográfica do rio Uberaba: uma abordagem metodológica

O presente estudo trata da avaliação da degradação ambiental da bacia do Rio Uberaba, situada no triângulo mineiro, com área de 241.904,30 ha, abrangendo os municípios de Uberaba, Veríssimo, Conceição das Alagoas e pequena porção de Planura. Neste estudo, foi produzido o mapa de degradação ambiental contendo quatro níveis: baixo, moderado, acentuado e severo. Os parâmetros utilizados nesta avaliação foram: vegetação, topografia, solo/geologia, potencial natural de erosão, mecanização, área agrícola, densidade populacional, pecuarização e área de conflito, aos quais foram atribuídos pesos. Para o nível de degradação “baixo”, foram definidos valores ≤ 13 pontos. Para o nível “moderado”, valores situados no intervalo de 14 a 16. Entre 17 e 19 pontos para o nível “acentuado”, e o nível “severo” com valores ≥ 20 pontos. Este estudo consolida as consequências do uso inadequado das terras, não respeitando a sua aptidão natural. As áreas com nível moderado de degradação representam 47%, áreas de nível acentuado (48%), e severo (4%) representam 52%, o que revela indício muito forte no avanço da destruição dos recursos naturais. As áreas classificadas com nível baixo representam apenas 1%, bastante inexpressiva, destacando o descaso na preservação dos recursos naturais.