Abstract

BIBIANO, Luvina; GARFIAS, J.  and  LLANOS, Hilario. Groundwater Hydrochemistry and Natural Softening Processes in Karstic Systems. Tecnol. cienc. agua [online]. 2015, vol.6, n.3, pp.57-78. ISSN 2007-2422.

Water from karstic springs contains high concentrations of total hardness from the dissolving of geological carbonate formations, which prohibits its use for domestic and industrial purposes in these zones. The approach used consisted of analyzing geochemical and natural softening process to estimate the factors that control water hardness in karstic areas. A series of water samples were taken throughout the hydrogeological system which included four main springs and three sites from channel flows. A change in the characterization of the water from HCO3-Ca-Na to HCO3-Ca-Na-Cl was observed in the direction of the flow, as was ionic enrichment attributable to the dissolving of minerals in the substrate. In addition, dedolomitization processes caused by the dissolving of evaporative minerals have been inferred. Nearly 60% of the samples were oversaturated with calcite, most as a result of the loss of dissolved CO2, which causes the natural softening of water. This evolution is caused by two physical changes which the flow undergoes as it travels its course- turbulence and aeration- which increase the air-water interface and the pH of the water, resulting in the precipitation of the hardness of the water. Future research aimed at predicting reaction rates should evaluate the degassing of CO2 which governs the softening of water in nature.

Keywords : Karst; water hardness; natural softening; calcite precipitation; CO2 degassing.

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