Hydrogeochemical and Isotopic Indicators of Vulnerability and Sustainability in the GAS Aquifer, São Paulo State, Brazil T
Journal of Hydrology: Regional Studies 14 (2017) 130–149 Contents lists available at ScienceDirect Journal of Hydrology: Regional Studies journal homepage: www.elsevier.com/locate/ejrh Hydrogeochemical and isotopic indicators of vulnerability and sustainability in the GAS aquifer, São Paulo State, Brazil T ⁎ Trevor Elliota, , Daniel Marcos Bonottob a School of Natural and Built Environment (SNBE), Queeńs University Belfast, Stranmillis Road, Belfast, BT9 5AG, Northern Ireland, UK b Instituto de Geociências e Ciências Exatas-IGCE, Universidade Estadual Paulista-UNESP, Av. 24-A No. 1515, P.O. Box 178, CEP 13506-900, Rio Claro, São Paulo, Brazil ARTICLE INFO ABSTRACT Keywords: Study region: The Guarani Aquifer System (GAS), São Paulo State, Brazil, an important freshwater Environmental Tracers (REEs, Br/Cl, B, δ11B, resource regionally and part of a giant, transboundary system. 87 86 Sr, Sr/ Sr) Study focus: Groundwaters have been sampled along a transect. Based on environmental tracers Groundwater (REEs, Br, B, δ11B, Sr, 87Sr/86Sr) aquifer vulnerability and sustainability issues are identified. Guarani Aquifer System (GAS) New hydrological insights for the region: For sites near to aquifer outcrop, REE and Sr signatures São Paulo State (and relatively light δ13C) trace possible vertical recharge from flood basalts directly overlying Aquifer vulnerability fi Aquifer sustainability the GAS. This highlights aquifer vulnerability where con ned by fewer basalts and/or having cross-cutting fractures. 14C activities for these waters, however, suggest the impact of this re- charge is significantly delayed in reaching the GAS. Anthropogenic sources for boron are not currently encountered; δ11B highlights feldspar dissolution, isotopically lighter signatures in the deepest sampled GAS waters resulting from pH/hydrochemical speciation changes down- gradient.
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