Hydrogeochemical and isotopic indicators of vulnerability and sustainability in the GAS aquifer, Sao Paulo State, Brazil

Autor(es)

Elliot, Trevor ^[1] ; Bonotto, Daniel Marcos ^[2]

Afiliação do(s) autor(es)

^[1] Queens Univ Belfast, SNBE, Stranmillis Rd, Belfast BT9 5AG, Antrim - North Ireland

^[2] Univ Estadual Paulista UNESP, IGCE, Ave 24-A 1515, POB 178, BR-13506900 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF HYDROLOGY-REGIONAL STUDIES; v. 14, p. 130-149, DEC 2017.
• Citações Web of Science: 1

Resumo

Study region: The Guarani Aquifer System (GAS), Sao Paulo State, Brazil, an important freshwater resource regionally and part of a giant, transboundary system. Study focus: Groundwaters have been sampled along a transect. Based on environmental tracers (REEs, Br, B, delta B-11, Sr, Sr-87/Sr-86) aquifer vulnerability and sustainability issues are identified. New hydrological insights for the region: For sites near to aquifer outcrop, REE and Sr signatures (and relatively light delta C-13) trace possible vertical recharge from flood basalts directly overlying the GAS. This highlights aquifer vulnerability where confined by fewer basalts and/or having cross-cutting fractures. C-14 activities for these waters, however, suggest the impact of this recharge is significantly delayed in reaching the GAS. Anthropogenic sources for boron are not currently encountered; delta B-11 highlights feldspar dissolution, isotopically lighter signatures in the deepest sampled GAS waters resulting from pH/hydrochemical speciation changes down-gradient. Br/Cl signatures (and heavier delta O-18, delta H-2) in these latter samples appear to reflect a past climatic signature emplaced under more arid conditions; carbon isotope systematics (delta C-13, C-14) support that these represent fossil waters, and care must be taken in their water resources management in regard to sustainability of abstraction. delta O-18, delta S-34 (sulfate) signatures confirm hydrological arguments that waters leak out of the base of the GAS aquifer in this locality rather than underlying formations with poorer water quality potentially mixing in, although other deep GAS waters in the region do show this inter-aquifer mixing. (AU)

• Processo FAPESP: 14/50743-2 - Environmental tracers of water resources management
• Beneficiário: Daniel Marcos Bonotto
• Modalidade de apoio: Auxílio à Pesquisa - Regular