Major Ions, Trace Elements and Isotope Characteristics of Groundwater from Coal Bearing Aquifer:A Case Study

Major ions, trace elements and isotope concentrations were determined in water samples collected from coal bearing aquifer and surface rivers in Suxian coalfield, China. The geochemical characteristics and ionic sources were discussed, and serious results could be obtained: The groundwater samples from coal bearing aquifers are mainly subdivided into Na-HCO₃ types, only one sample be Na-SO₄ type, presenting different features with surface river water. The total REE concentrations (ΣREE) in groundwater samples are low with average value of 0.29 mg/L. The light rare earth elements in groundwater are less compared with high rare earth elements, evidenced by the small value of Nd_SN/Yb_SN. The reduction environment and organic matter in coal bearing aquifers are the reasons deduced the positive Ce anomalies in groundwater samples, while the surrounding feldspar rocks controlled the positive Eu anomalies. The concentrations of δ¹⁸O and δD in groundwater samples are lower than river water samples, reflected the river waters affected by the evaporation clearly, with the heavy isotope enrichment. The evaporation and rock weathering affection is the mainly factors on the ionic source in groundwater samples, evidenced by the Gibbs diagrams and other ionic group ratios such as HCO₃^-/Na⁺-Ca²⁺/Na⁺ and Mg²⁺/Na⁺-Ca²⁺/Na⁺.