HYDROGEOCHEMICAL CHARACTERISTICS OF SHALLOW GROUNDWATER IN THE SUNAN COAL-MINING DISTRICT, NORTHERN ANHUI PROVINCE, CHINA AND ITS SIGNIFICANCE

Conventional hydrogeochemical data and hydrogen and oxygen stable isotopes were applied for studying the hydrochemical characteristics of the shallow groundwater in the Sunan coal-mining district, Northern Anhui Province, China, and to identify the main hydrogeochemical processes and formation mechanisms. The result showed that the groundwater samples presented neutral. The groundwater was dominated by the HCO3- Ca·Mg and HCO3-Na+K·Mg·Ca types, with high concentrations of Na+ and HCO3- in cations and anions, respectively. Apart from HCO3- at two sampling points, the concentrations of all major ions and total dissolved solid (TDS) were below the permissible limits of the World Health Organization (WHO). Analysis using hydrogen and oxygen stable isotopes indicated that δ values of the shallow groundwater were mostly below precipitation line of local and surface water line of the coal district, and precipitation or surface water was major replenishment of the aquifer. The mixing action of groundwater had little effect on the δD and δ18O values even if TDS had an increasing tendency along the groundwater-flow direction. A Gibbs plot suggested that the major ion chemistry of the groundwater was primarily controlled by weathering of rocks, and that the first aquifer in the Sunan coal-mining district was a relatively closed system.