Geochemistry and background concentration of major ions in spring waters in a high-mountain area of the Hamedan (Iran)

Abstract

Little is known about the natural phenomena that govern the chemical composition of spring waters in Alvand mountain ecosystem. A total of 50 spring water samples of the Avand mountains, Hamadan, western Iran were collected and analyzed for the main components in an effort to both identify ion chemistry and establish background concentrations of major ions and some trace elements (Cd, Fe, Mn, Ni, Zn).The order of relative abundance of major cations in the spring waters was Ca, Mg, Na, K, while that of anions was HCO3, Cl, SO4, NO3. Most spring water samples were undersaturated with respect to calcite. The major water types in spring waters were Ca–HCO3 (group 1), CaHCO3–Cl, CaMg–HCO3Cl, and CaMg–Cl–HCO3 (group 2), which were mainly due to the dissolution of carbonate minerals and silicate weathering and partly due to the ion exchange. Activity diagrams showed that spring waters fall into the kaolinite field due to the short interaction with silicate minerals. In general, mineralization, pH, mean concentrations of Ca, Mg, HCO3, TDS, saturation indices of calcite, dolomite and PCO2 were greater in water samples from the group 1 than in water samples from group 2. Spring waters were mainly soft water (84%) in group 2 and hard water (16%) in group 1. The factor analysis performed on spring water samples identified four factors controlling their variability in spring water samples. Four extracted factors explained 84.7% of data set variance. Factor 1 had the highest factor loadings of EC, HCO3, SO4, Cl, Ca, Mg, Na, Mn, Cd, Ni, and Fe, while factor 2 had the highest factor loadings of Zn. Factors 3 and 4 had the highest factor loading for NO3, P and K, respectively. Factors 1, 2 and 4 together may be related to the dissolution of carbonate minerals (group 1) and silicate weathering, while factor 3 may be due to the anthropogenic input. Different statistical methods were used in the evaluation of background values of the spring waters. Trace element concentration in spring waters was low and associated with local mineralogy.