DEGEO - Departamento de Geologia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8
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Resultados da Pesquisa
Item Recharge sources and hydrochemical evolution of an urban karst aquifer, Sete Lagoas, MG, Brazil.(2017) Galvão, Paulo Henrique Ferreira; Hirata, Ricardo; Halihan, Todd; Terada, RafaelThe current water supply for the city of Sete Lagoas, Brazil, is almost entirely groundwater from the Sete Lagoas Karst Aquifer, with a small contribution from a fractured-basement rock aquifer. Characterizing the hydrogeologic processes is important for proper water resource management, avoiding contamination and other future issues. The main goal of this study is to identify active hydrogeological processes, such as possible surface– ground water interactions, sources of recharge, and the hydrochemical evolution of groundwater through the use of stable isotopes 18O and 2H and major ion data. The groundwater samples were collected from the karst aquifer (central urban area) and from the fractured aquifer (southern part of the city). Surface water samples were collected from the seven main lakes, and rainwater was sampled over a period of one year. The stable isotope results indicated the groundwater origin is directly from local precipitation, having a limited recharge period, and locally receiving surface water contributions. Groundwater quality in the central urban area may be influenced by surface water infiltration where the karst aquifer is in contact with overlying unconsolidated sediments. Some samples with nitrate concentration of 10 mg/L or higher indicates the natural composition of the groundwater has been altered by urban sewage contamination. The highest concentrations of major ions were found in the central region, where the most karstified area from the Sete Lagoas Formation is located. These data suggest a longer residence time for this water, indicating more mineralization, in accordance with the geological information.Item Influence of the natural oxidation of the leachate organic fraction from a landfill on groundwater quality, Belo Horizonte: Minas Gerais, south-eastern Brazil.(2013) Barella, Cesar Falcão; Bacellar, Luis de Almeida Prado; Nalini Júnior, Hermínio AriasThe objective of this work was to evaluate the influence of the natural degradation of the leachate organic fraction from the Belo Horizonte landfill on groundwater chemical evolution. The work focused on the modifications introduced by redox reactions in the presence of terminal electron acceptors. Twenty-one sampling points distributed along 13 monitoring wells were selected for the analysis of the chemical indicators of interest (TDS, SO4 -2, Fe?2, Ba, pH and Eh). The behaviour of the variables involved in the alteration of the water quality was assessed by the spatial distribution of target parameters, elaboration of redox diagrams and chemical modelling that focused on the determination of mineral saturation indexes. The study showed a trend toward pyrite precipitation, which leads to the removal of chemical species such as divalent iron and sulphur as sulphide from the system. This removal disturbs the chemical equilibrium, typically by moving the reactions to replenish the sulphate concentration present in the groundwater. This process occurs primarily through the dissolution of compounds that have sulphate in their chemical composition, such as barite, suggesting that part of the barium concentration in the subsurface can be of geogenic origin. This study demonstrated the importance of knowing the nature of the geochemical processes in groundwater contaminated by urban solid waste.Item Arsenic in the groundwater of Ouro Preto (Brazil) : its temporal behavior as influenced by the hydric regime and hydrogeology.(2007) Gonçalves, José Augusto Costa; Lena, Jorge Carvalho de; Paiva, José Fernando de; Nalini Júnior, Hermínio Arias; Pereira, Janice CardosoIn the city of Ouro Preto (MG), water catchment for public supply originates from superficial drainage, springs, old abandoned mines and some driven wells. In the rocks of the region, As is originally found in gold-enriched sulphide-bearing mineral deposits. The weathering process introduces As into the hydrological system by dissolution of this element into the leachate. Measurement of the As content in the groundwater of some catchments was carried out during 1 year and these measurements demonstrated high As content—up to 224 lg L–1 of As(V)—during the rainy season (the maximum concentration limit according to World Health Organization is 10 lg L–1). Lower values were observed during the dry season and in some sampling stations, As was not even detected. The As concentration variability during 1 year shows a strict and direct relationship to seasonal and hydrological conditions. For city authorities, responsible for public water supply, it is necessary to perform a complete inventory of the water sources used and constantly monitor the As content in the water.Item Study of flow in vadose zone from electrical resistivity surveys.(2008) Morais, Fernando de; Bacellar, Luis de Almeida Prado; Aranha, Paulo Roberto AntunesEntre os métodos indiretos aplicados ao monitoramento ambiental, a eletrorresistividade tem desempenhado um papel importante no entendimento do fluxo de água na zona não saturada dos solos e, consequentemente, na recarga dos aquíferos. Neste trabalho, pretende-se avaliar a influência de algumas propriedades pedo-geomorfológicas na infiltração e percolação de água pelos horizontes superficiais dos solos por meio de seções de eletrorresistividade multitemporais. Os experimentos foram efetuados em duas áreas com características pedo-geomorfológicas distintas em região com rochas do embasamento cristalino do sudeste do Brasil. A primeira á situada numa encosta com formas côncavas em planta e em perfil (cabeceira de drenagem anfiteátrica), com predomínio de argissolos. A segunda área se situa numa encosta com forma convexa em planta e em perfil, com predomínio de latossolos. Os resultados provam a eficiência da eletrorresitividade para identificar percolação em solos tropicais, mesmo quando há diferenças sutis das propriedades hidráulicas. Foi também possível confirmar que a percolação é mais rápida na encosta com forma convexa do que na encosta com forma côncava.Item Estimativa de parâmetros de aquíferos através do coeficiente de recessão em áreas de embasamento cristalino de Minas Gerais.(2010) Silva, Rebeca Ferreira Gonzaga; Bacellar, Luis de Almeida Prado; Fernandes, Kênia NassauO coeficiente de recessão (α) indica a taxa de produção do fluxo de base, que representa a porção da vazão de um rio mantida pela restituição de águas subterrâneas. Ele pode ser obtido através da análise de hidrogramas. Esse coeficiente possibilita o cálculo de parâmetros importantes, como a transmissividade de aquíferos, as reservas renováveis de água subterrânea e as vazões mínimas em canais de drenagem, que, usualmente, são obtidas através de outros índices hidrológicos, como o Q7,10, muito empregado na gestão de recursos hídricos superficiais. As bacias estudadas estão localizadas na porção centro-sul de Minas Gerais, em regiões de rochas granito-gnássicas, sob vegetação, clima e uso e ocupação semelhantes. Os resultados obtidos, no estudo, foram satisfatórios, indicando os métodos de determinação de coeficiente de recessão como promissores para se caracterizar a produção de água subterrânea em bacias hidrográficas do embasamento cristalino. A restituição de águas subterrâneas para os sistemas de drenagem é maior nas áreas de relevo mais suave, indicando que estas constituem as melhores áreas de recarga.