Flow modeling and hydrogeochemical inversion calculations were performed on the aquifer systems of the Crato-Juazeiro Graben in the Araripe Sedimentary Basin of the Cariri Valley, Northeast Brazil, in order to assess aquifer interconnections through an aquitard of the Araripe Plateau. Steady state hydraulic head numeric calculations with the finite difference method used Modflow software with hydrologically based boundary conditions and a piezometric surface as initial condition. Hydrogeochemical inversion with PHREEQC was performed for two water samples representing typical initial and final waters along the flow path. Flow simulation shows that approximately 20% of all recharge water from the superior aquifer system passes through the Santana aquitard reaching the middle aquifer system. Quantification of mineral dissolution/precipitation processes, ion exchange and microbiological redox reactions taking place in the aquifer systems also
Foi traçada a evolução hidroquímica através de uma inversão hidrogeoquímica, utilizando o aplicativo PHREEQC, para calcular a transferência molar de minerais entre a água mineralizada e o meio por onde ela flui, ocorrida entre os Sistemas Aqüíferos Superior e Médio da Chapada do Araripe, localizada na região nordeste do Brasil, ao sul do Estado do Ceará, noroeste de Pernambuco e Sudeste do Piauí. A inversão hidroquímica foi realizada a partir de duas amostras d'água: uma com características do Sistema Aqüífero Superior, a água inicial, e outra com características do Sistema Aqüífero Médio, a água final, suposta evoluída hidrogeoquimicamente da água inicial. Na inversão hidroquímica foram considerados processos de precipitação e/ou dissolução de minerais contidos nas rochas das formações geológicas por onde a água flui, trocas iônicas com argilominerais, além de reações redox características da presença de matéria orgânica e microorganismos em subsuperfície. Os resultados estão de acordo com a existência de conexões hídricas entre os diferentes sistemas aqüíferos concordando com o modelo fenomenológico para a circulação de água subterrânea proposto para a região.
Factor analysis was applied to 56 groundwater samples collected from wells located in the Araripe Sedimentary Basin, in the north-east of Brazil. The parameters are a set of 9 physicochemical, chemical, and isotope data, constituted by electrical conductivity (EC), ionic concentrations of Ca 2+ , Mg 2+ , Na + , K + , Cl − , SO 4 2− , alkalinity and δ 18 O 0 / 00 . In R-mode factor analysis, the first 3 factors explain 62% of the variance, their loadings allowing the interpretation of hydrogeochemical processes that take place in the area. Q-mode factor analysis on the 56 water samples decreases space dimensionality to 6, explaining 93% of the total database information. With the aid of a scalar and angular measurement method, objects were clustered, resulting in 11 groups classified according to their inherent characteristics, related to their hydrogeological origin.
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