Recharge sources and hydrochemical evolution of an urban karst aquifer, Sete Lagoas, MG, Brazil.
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2017
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Resumo
The current water supply for the city of Sete
Lagoas, Brazil, is almost entirely groundwater from the
Sete Lagoas Karst Aquifer, with a small contribution from
a fractured-basement rock aquifer. Characterizing the
hydrogeologic processes is important for proper water
resource management, avoiding contamination and other
future issues. The main goal of this study is to identify
active hydrogeological processes, such as possible surface–
ground water interactions, sources of recharge, and the
hydrochemical evolution of groundwater through the use of
stable isotopes 18O and 2H and major ion data. The
groundwater samples were collected from the karst aquifer
(central urban area) and from the fractured aquifer
(southern part of the city). Surface water samples were
collected from the seven main lakes, and rainwater was
sampled over a period of one year. The stable isotope
results indicated the groundwater origin is directly from
local precipitation, having a limited recharge period, and
locally receiving surface water contributions. Groundwater
quality in the central urban area may be influenced by
surface water infiltration where the karst aquifer is in
contact with overlying unconsolidated sediments. Some
samples with nitrate concentration of 10 mg/L or higher
indicates the natural composition of the groundwater has
been altered by urban sewage contamination. The highest
concentrations of major ions were found in the central
region, where the most karstified area from the Sete Lagoas
Formation is located. These data suggest a longer residence
time for this water, indicating more mineralization, in
accordance with the geological information.
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Stable isotopes, Major ions, Hydrogeology, Groundwater
Citação
GALVÃO, P. H. F. et al. Recharge sources and hydrochemical evolution of an urban karst aquifer, Sete Lagoas, MG, Brazil. Environmental Earth Sciences, v. 76, p. 159, 2017. Disponível em: <https://link.springer.com/article/10.1007%2Fs12665-017-6482-3>. Acesso em: 25 ago. 2017.