Hydrogeochemical Study of Water Resources in Shahid Hashemi-Nejad Gas Refinery and Surrounding Areas Using Compound Diagrams, Saturation Indices and Ionic Ratios

Hydrogeochemistry of surface and ground waters is a useful way to identify performing reactions in aquifers and also in recognizing effective natural and anthropogenic polluting factors in these sources. In order to study surface and ground waters quality of shahid Hashemi- Nejad gas refinery region، located 35 km south of Sarakhs town، 17 water samples were collected. Parameters of pH، temperature، electrical conductivity and total dissolved solids were measured in the field، and water samples were analyzed for major anions and cations concentrations in geochemical lab. Using Piper diagram، sodium sulfate and sodium chloride type and facies were determined for the water samples. Ca2+/Mg2+ v. as Mg2+، Ca2+/Ca2++Mg2+ v. as SO42-/SO42-+HCO3- compound diagrams، total hardness and PCO2 proved carbonates dissolution. Na+/Na++Cl-، Ca2+/Ca2++SO42-، HCO3-/Σ anions، HCO3-/SiO2، SiO2/Na++K+-Cl-، Na++K+ and SO42-+Cl- ionic ratios determined factors such as ion exchange، dissolution of Gypsum، Halite and sulfates of sodium-potassium، and weathering of carbonates and silicates as the most important effective parameters on chemical composition of water sources in this area. In Log (aCa2+/a(H+) 2) and Log (aMg2+/a(H+) 2) v. as Log (aNa+/a(H+) 2) diagrams، which are used for specifying soluble silicate minerals in water، all water samples showed the dissolution of Kaolinite except two samples which were located at clinochlore mineral zone. Calculating saturation indices using PHREEQC software proved that Calcite and Dolomite mineral had supersaturation، Halite and Anhydrite undersaturation and Gypsum mineral supersaturation، undersaturation and equilibrium states in all samples. Schoeller and Wilcox diagrams pointed unsuitable quality for drinking and agricultural usages for these water sources. In fact، because of formations presence with high solubility that lay out in large amount of surface، water resources in this area have not suitable quality، and on the other hand shallow water level and high temperature intensify it. Based on obtained results، natural factors have major role in quality area’s water resources.