Isotopic characteristics of D, ¹⁸O, ¹³C_dic, ¹⁸O_dic, ⁸⁷Sr/⁸⁶Sr and their application in coal mine water: a case study

In order to understand the isotopic characteristics of coal mine water in diverse aquifers, ten groundwater samples were collected from three aquifers – Quaternary (QA), Coal-bearing (CA), and Limestone (LA) – in Xutuan coal mine, Anhui Province, China. The geochemical characteristics of major ions and isotopes were determined, and the results showed that all of the groundwater samples are HCO₃-Na·K or Cl-Na·K types. The concentrations of Na⁺ + K⁺ decreased in the order CA > QA > LA, whereas the content of Ca²⁺ and Mg²⁺ increased from CA to LA. Groundwater in LA is meteoric in origin, while that in QA is clearly influenced by surface water. The δ¹³C_dic and δ¹⁸O_dic in groundwater samples from LA, QA and CA are influenced by the surrounding strata, CO₂ and microorganism activity, respectively. The strontium concentration decreases in the sequence LA > CA > QA, but water samples from CA give the highest value of ⁸⁷Sr/⁸⁶Sr. Strontium is released by dissolution from the surrounding rock, and the ⁸⁷Sr/⁸⁶Sr ratio could be used to identify the groundwater source.