Anomalous content of chromium in a Cretaceous sandstone aquifer of the Bauru Basin, state of Sao Paulo, Brazil

Autor(es)

Bertolo, Reginaldo ^[1] ; Bourotte, Christine ^[2] ; Marcolan, Leonardo ^[1] ; Oliveira, Sonia ; Hirata, Ricardo ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Geosci, Lab Phys Models LAMO, BR-05508080 Sao Paulo - Brazil

^[2] Univ Sao Paulo, Sch Arts Sci & Humanities EACH, BR-03828000 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of South American Earth Sciences; v. 31, n. 1, p. 69-80, FEB 2011.
• Citações Web of Science: 15

Resumo

Anomalous and natural concentrations of Cr(6+), occasionally exceeding the permitted limit for human consumption (0.05 mg/L), have been detected in groundwater in the northwestern region of the state of Sao Paulo. As part of a water-rock interaction investigation, this article describes the chemical and mineralogical characterization of rock samples taken from boreholes in the municipality of Urania, with the objective of identifying Cr-bearing minerals and determining how chromium is associated with these minerals. Rock sample analysis were performed using X-ray Fluorescence, X-ray Diffraction, Scanning Electron Microscopy, electron microprobe and sequential extraction techniques. Chemical analyses indicated that the quartzose sandstones show a geochemical anomaly of chromium, with an average content of 221 ppm, which is higher than the reported chromium content of generic sandstones (35 ppm). Diopside was identified as the primary Cr-bearing mineral potentially subject to weathering processes, with a chromium content of up to 1.2% as Cr(2)O(3). Many of the diopside grains showed dissolution features, confirming the occurrence of weathering. Sequential extraction experiments indicated that 99.3% of the chromium in samples is tightly bonded to minerals, whereas 0.24% is weakly bonded via adsorption. Assuming hypothetically that all adsorbed chromium is released via desorption, the theoretical Cr concentration in water would be one order of magnitude higher than the concentrations of Cr(6+) detected in groundwater. (C) 2010 Elsevier Ltd. All rights reserved. (AU)

• Processo FAPESP: 97/13879-6 - Os mecanismos controladores da partição do cromo no sistema rocha-solo-água no aquífero Bauru, Noroeste do estado de São Paulo
• Beneficiário: Ricardo César Aoki Hirata
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 98/15340-0 - Hidrogeologia e modelagem hidrogeoquímica da zona não saturada do Aquífero Adamantina
• Beneficiário: Reginaldo Antonio Bertolo
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 05/60502-3 - Complementação da investigação hidrogeoquímica do cromo no Aquífero Adamantina em Urânia, SP
• Beneficiário: Reginaldo Antonio Bertolo
• Modalidade de apoio: Auxílio à Pesquisa - Regular