Distribution and enrichment of strontium in the Zigui karst watershed

In order to explore the distribution and enrichment of strontium in groundwater under the control of water flow system in karst area, the Maoping river and Jiuwanxi karst watershed in Zigui were taken as the study case, and 415 groups of water samples and 93 groups of rock samples were collected from typical springs, typical surface water and main water-bearing rocks during 2016-2018. The analytical results indicate that strontium is mainly enriched in the strata of the Jialingjiang Formation, Loushanguan Formation and Dengying Formation deposited in tidal flat and lagoon sedimentary facies, and mostly exists in the form of celestite, strontianite and other minerals. The water type of Sr-rich groundwater is mainly SO₄ type, Cl type, and SO₄-HCO₃ type. In the water flow system, ,the strontium-rich minerals are less in strata above vadose zone, mainly affected by leaching; both celestite and strontianite are not saturated in shallow groundwater, but they tend to be saturated in a few deep groundwater. The closed reduction environment rich in gypsum and celestite is conducive to the enrichment of strontium in groundwater.