33 resultados para Sistema Aqüífero Guarani
em Repositório Institucional UNESP - Universidade Estadual Paulista "Julio de Mesquita Filho"
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Pós-graduação em Geociências e Meio Ambiente - IGCE
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Pós-graduação em Geociências e Meio Ambiente - IGCE
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This work evaluated the hydrogeochemistry of the Guarani Aquifer in the urban area of Ribeirão Preto, São Paulo State. Thirty one sampling points were established and it was carried out field campaigns in 7 and 8 July 2005, analyzing the following parameters: conductivity, temperature, pH, turbidity, color, dry residue, dissolved oxygen, Ca2+, Mg2+, Na+, K+, Fe3+, Al3+, HCO3-, SO42-, PO43-, NO3-, Cl- and F-. The results indicated that the groundwaters in the urban area of Ribeirão Preto pH possess slightly acid, low conductivity, turbidity, color and dissolved oxygen inside the limits established for drinking waters. The ionic composition indicated that the groundwaters have low cations and anions concentration, being they classified as soft water and calcium-bicarbonated. Statistical tests suggested that conductivity and pH are controlled for the calcite dissolution (CaCO3) during the water/rock interaction process. Besides, it is possible to conclude that the high NO3- and PO43- concentrations found in the groundwater in the urban area of Ribeirão Preto are originated due to anthropogenic activities.
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Several geothermometers have been employed to determine the expected temperature in the groundwater reservoirs, most part of them based on the chemical equilibrium between thermal groundwaters and minerals which constitute the aquifer framework. Based on this principle, groundwater from Guarani Aquifer System, which presents temperatures upon to 38°C, classified as hyperthermal by the Brazilian Mineral Water Code, had their chemical composition evaluated with the main purpose to determine the expected temperatures in the reservoir based on the application of several geothermometers. These groundwaters can be classified as Na-HCO3 type evolving to Na-HCO3-Cl-SO4 type due the increase in sulphate and chloride concentrations. Measured groundwater temperatures show a good correlation with the depth of the aquifer, indicating an average geothermal gradient of 27.7°C/km. The lowest geothermal gradients, bellow 25°C/km, are observed in the central portion of the study area; meanwhile the highest gradients are observed in NE and W portions of the study area. Quartz equilibrium based geothermometers return temperature over the measured temperatures, meanwhile chalcedony geothermometer returns temperatures near the measured in the wells, except for the wells located in the area which presents the lowest geothermal gradients. The geothermometers based on the equilibrium between Na/K have returned temperatures diverse from the measured at the field, meanwhile the geothermometer based on the equilibrium between Na/K/Ca has presented good match with groundwater which present temperatures under 50°C, due the thermodynamic equilibrium between these waters and feldspars. Geothermometers show evidences about mixtures between groundwaters from GAS and underlying units, especially in wells located in the SW portion of the study area.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Pós-graduação em Geociências e Meio Ambiente - IGCE
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Pós-graduação em Agronomia (Irrigação e Drenagem) - FCA
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Pós-graduação em Agronomia (Irrigação e Drenagem) - FCA
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Pós-graduação em Agronomia (Irrigação e Drenagem) - FCA
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Pós-graduação em Geociências e Meio Ambiente - IGCE