Hydrochemistry Characteristics of Groundwater from Ordovician Limestone Aquifer in Suxian Coal Mine, Anhui Province, China

Major ions, trace elements and isotope concentrations were measured in water samples collected from Ordovician limestone aquifer and surface rivers in Suxian coal mine district, China. The geochemical characteristics and hydrochemistry process were discussed, and serious results could be obtained: Groundwater samples from Ordovician limestone aquifer were mainly the Na-SO₄ and Na-HCO₃ types, the similar feature with the river water samples suggesting a certain relationship may be existed between groundwater and surface river water. The total REE concentrations (ΣREE) in groundwater samples varied from 0.0263 to 0.1348 mg/L, with an average value of 0.063 mg/L. The oxidative conditions are the mainly factors deduced the negative Ce anomalies and positive Eu anomalies. The groundwater samples, recharged by the precipitation and surface water, have lower concentrations of δ¹⁸O and δD comparing with river water, reflected the river water affected by the evaporation clearly, with the heavy isotope enrichment. The negative correlation between δ¹⁸O and TDS and Ca²⁺ indicated that the dissolution of limestone could be the factor influencing the oxygen isotope characters. Groundwater in Ordovician limestone is runoff from both sides to intermediate, with the Taoyuan coal mine as the subsidence center in study area, evidenced by the contour diagrams of TDS and δ¹⁸O. The hydrochemistry field and runoff field of groundwater in study area are mainly controlled by the tectonic field, especially the Sunan syncline.