Mineral saturation index characteristics, sources of Sr²⁺, SO₄²⁻ and development potential of strontium−rich karst water in Xintian County, Hunan Province

This paper is the result of hydrogeological survey engineering.

Objective There is limited research on the sources of strontium elementand the potential for the development and utilization of karst water in the large−scale strontium rich mineral water field in Xintian County, Hunan Province. Exploring the hydrochemical characteristics of strontium−rich karst water and the sources of strontium element can provide theoretical support for searching for strontium rich groundwater in karst areas.

Methods PHREEQC software, water stoichiometry, end element method and hydrogeological parameters were used in this study to reveal the mineral saturation index characteristicsof strontium−rich karst water, as well as the sources of Sr²⁺ and SO₄²⁻ and its development potential through the hydrogeological investigation and hydrochemical testson groundwater in this strontium−rich mineral water field.

Results Calcite is mainly saturated both in the springs and shafts, while dolomite changes from unsaturated in the springs to saturate in the shafts. Strontium is saturated in the shafts, and gypsum is unsaturated both in the springs and the shafts. In the springs, mineral saturation index increases with the total dissolved solids, and they areof a good positive correlation, but of a poor correlation in the shafts. The correlation of SO₄²⁻ betweenthe springs and shaftsare positive. According to the stoichiometric relation of Ca²⁺, Mg²⁺, Sr²⁺, HCO₃⁻ and SO₄²⁻, SO₄²⁻ in the shafts may come from gypsum dissolution. The Sr²⁺ in the springsare mainly derived from strontium which replaces calcium with isomorphism in limestone, while Sr²⁺ in the shafts probably come from strontium siderite in the aquifer. 85.2% of the groundwatersamplings in the research area meet the national standard for drinking water quality, and the excess water samplings are mostly single indicator exceeding the standard. Through calculation, the natural recharge resources, exploitable resources and groundwater resource potential of strontium−rich groundwater in dry years are 3.83×10⁷ m³/a、1.05×10⁷ m³/a、7.28×10⁶ m³/a respectively.

Conclusions Strontium in the strontium−rich groundwater in Xintian County is mainly derived from the dissolution of strontium−containing minerals in Shetianqiao Formation strata of Devonian. Those minerals, including strontianite, were form by isomorphicly substitute of calcium with strontium. The amount and resource potential of strontium−rich groundwater are considerable, with a great value for development and utilization.