Hydrochemical characteristics and evolution mechanisms of the groundwater in the lower reaches of Hangshui river
The lower reaches of the Huangshui river was selected as a typical study area,and the hydro-chemical composition of shallow groundwater in this area was analyzed employing multivariate statisti-cal analysis,Piper three-line diagram,Gibbs diagram,silicate stability field diagram,ion ratio,calcu-lation of water-soluble composition and reverse hydrogeochemical simulation.The results show that:(1)From the southeast to northwest of the study area,the concentrations of TDS and Cl gradually in-creased,and the water quality changed from freshwater to salt water.The dominant anion types of groundwater were along HCO3→HCO3·Cl→Cl·HCO3→Cl changes.Na+and Ca2+were the major cation in most regions.(2)The weathering and dissolution of carbonate rock,evaporite and aluminosil-icate were the main hydrogeochemical processes in the groundwater in this area.Besides,there was the positive cation alternate adsorption.(3)The results of reverse hydrogeochemical simulation quantita-tively verified that the chemical composition of groundwater in the upper and middle reaches of Huang-shui river was mainly controlled by rock weathering,the groundwater in the lower reaches was mainly affected by seawater intrusion,and cation exchange occurred under the influence of seawater intrusion.
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