Influencing factors of the hydrochemical characteristics of surface water and shallow groundwater in the subsidence area of the Huainan Coalfield

To determine the hydrochemical characteristics and the factors affecting the water bodies in the Huainan Coalfield, 101 samples of surface water (river water and water in subsidence) and groundwater in the study area were collected in August and December 2016 and analyzed for their mass concentrations, compositions, and types of major ions. The formation and factors affecting the hydrochemical characteristics of the water bodies were analyzed with the ratio of elements, Gibbs diagram and factor analysis. The results suggest that the mass concentrations of the total dissolved solid (TDS) in the water bodies follow the order of water in subsidence > river water > groundwater. The hydrochemical type of the surface water was determined to be a HCO3·Cl-Na type, and the groundwater was determined to be a HCO3−Na·Ca type. The hydrochemical characteristics of the surface water were mainly formed by evaporation. The weathering of the water body was dominated by evaporites, followed by silicate weathering. The ions in the groundwater were mainly derived from the weathering of silicate rocks. Human activities have also exerted effects on the hydrochemical characteristics of the water in subsidence.