Hydrochemical and stable isotopes (H, O, S) signatures in deep groundwaters of Paraná basin, Brazil.

This paper describes a hydrochemical (major and trace elements) and stable isotopes (H, O, S) study of rainwater and groundwater in a Guarani Aquifer System (GAS) transect at São Paulo State, Brazil. The Brazilian Code of Mineral Waters (BCMW) was adopted for the groundwater temperature classification, allowing adequate insights in the hydrochemical data. H and O data in circa 580 rainwater samples at São Paulo State have been selected, showing a wide dispersion (δO from −21.5 to +4.9 ‰ V-SMOW; δH from −162 to +43.2 ‰ V-SMOW). The H and O data in groundwater did not vary significantly, fitting the regional meteoric water line and indicating that the groundwater origin is directly related to the meteoric water precipitation. The δO values in groundwater collected along the GAS transect did not indicate a tendency towards more negative values according to the groundwater flow direction at São Paulo State as suggested elsewhere. The δO and δO data indicated that the dissolved sulfate is obtained from previous sulfate dissolution. The δS and δO data of dissolved SO suggested that the dissolution of evaporites and bacterial SO reduction processes may be occurring at the GAS. The temperature, redox potentials, dissolved oxygen and organic matter content in the sediments provided an ideal environment for the δS and δO changes along the GAS transect, accompanying the groundwater flow direction. [ABSTRACT FROM AUTHOR]