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|Title:||HIDROGEOQUÍMICA NAS CAVAS DE EXTRAÇÃO DE AREIA NA REGIÃO DO BAIRRO PIRANEMA DISTRITO AREEIRO DE SEROPÉDICA-ITAGUAÍ RJ.|
|Keywords:||hidrogeoquímica; cavas de extração de areia; intemperismo; aqüífero; Piranema; águas ácidas; Hidrogeoquímica; cavas de areia; intemperismo; aqüífero Piranema; hydrogeochemistry; sand extraction pits; weathering; Piranema aquifer; acidic waters|
|Abstract:||Seropédica-Itaguaí Sand Mining District has an important role to the Rio de Janeiro Metropolitan Region, supplying about 90% of the sand to its civil construction. The sand extraction process is fact by the remove of the surface sedimentary layers (quartzfeldspatic composition), make water table to fill up the produced pits. However, this activity provides some chemical and physical-chemical changes in that water. Four sand pits were monitored in the period between January 2004 and November 2005, that aims to characterize the hydrogeochemical process that occurs in that water, providing information to the transformation of the pits in ponds for fish culture at the end of mining activities. The results show low values of pH (3,11 5,2) and high concentrations of sulfate (3 97,64 mg.L-1) in those waters and it must be given by oxidation reactions on reduced sedimentary materials with some sulfide content, caused by the sand extraction. Anomalous values for aluminum (> 10 mg.L-1) are fact by the low pH of the analyzed waters, which increase the aluminosilicate minerals solubility (feldspars and micas). However, aluminum concentrations show that are controlled by pluviometric precipitation, or be, the aluminum concentrations are bigger as much as minor the pluviosity. Besides this fact, the silica content in the extraction holes, which is in colloidal form, could contribute for the aluminum content reduction through the reaction between aluminum and silica, resulting in the formation of an aluminosilicate (imogolite). Iron and manganese are, respectively, precipitated as hydroxides (Fe3+) and dissolved form as Mn2+. Chloride has constant concentrations in those waters by its conservative characteristic and is originated by atmospheric deposition (marine aerosols). The weathering in the extraction holes was characterized by the calcium, magnesium,potassium, sodium and silica concentrations. The weathering rating is incipient, where the stability diagrams pointed out the water equilibrium with primary minerals and montmorillonite clays, consequently, presenting the bisialitization as the predominant weathering type. For the transformation of the sand extraction pits in fish culture ponds, must be considered the aluminum geochemistry because its toxicity on these individuals.|
|Appears in Collections:||TEDE sem arquivo|
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