Hydrochemistry of the Groundwater from Coastal Aquifer in Amol-Ghaemshahr Region, Mazandaran Province, North Iran

Present study is an attempt to understand the hydrochemical characteristics of groundwater in Amol- Ghaemshahr region, Mazandaran province in North Iran. Groundwater samples were randomly collected from 77 wells in Amol-Ghaemshahr plain having different depths, varying from 2.4 m to 198 m. The physicochemical parameters such as pH, electrical conductivity (EC) and total dissolved solids (TDS) were measured in addition to major cation and anion concentrations. The abundance of major ions is as follows: Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ and HCO₃^- > Cl^- > SO₄^2- > NO₃^-. Thematic maps pertaining to pH, TDS, EC, Cl^-, NO₃^-, SO₄^2- and Na⁺ were presented in Geographical Information System (GIS) based maps. Different classes in thematic maps were categorized as desirable, permissible and unpermissible based on WHO standards for drinking purposes. The chemistry of water samples from coastal aquifer was interpreted by using classical Piper diagrams. The study indicates that Ca-Mg-HCO₃ and Ca-Mg-Cl are the dominant hydrochemical facies followed by Na-Cl and Ca-Mg-SO₄ facies. Gibb's plot reveals that the mechanisms responsible for controlling chemical composition of the groundwater are both rock-water interaction and evaporation.