ABSTRACT

The Harzandat plain is part of the East Azerbaijan province, which lies between Marand and Jolfa cities, northwestern of Iran, and its groundwater resources are developed for water supply and irrigation purposes. The main lithologic units consist chiefly of limestone, dolomite, shale, conglomerate, marl, and igneous rocks. In order to evaluate the quality of groundwater in study area, 36 samples were collected and analyzed for various ions. Chemical indexes like sodium adsorption ratio, percentage of sodium, residual sodium carbonate, and permeability index were calculated. Based on the analytical results, groundwater in the area is generally very hard, brackish, high to very high saline and alkaline in nature. The abundance of the major ions is as follows: Cl(-) >HCO3(-)>SO4(2-) and Na(+) >Ca(2+) >Mg(2+) >K(+). The dominant hydrochemical facieses of groundwater is Na(-)Cl type, and alkalis (Na(+), K(+)) and strong acids (Cl(-), SO4(2-) are slightly dominating over alkali earths (Ca(2+), Mg(2+)) and weak acids (HCO3(-), CO3(2-). The chemical quality of groundwater is related to the dissolution of minerals, ion exchange, and the residence time of the groundwater in contact with rock materials. The results of calculation saturation index by computer program PHREEQC shows that nearly all of the water samples were supersaturated with respect to carbonate minerals (calcite, dolomite and aragonite) and undersaturated with respect to sulfate minerals (gypsum and anhydrite). Assessment of water samples from various methods indicated that groundwater in study area is chemically unsuitable for drinking and agricultural uses.

In the study area, groundwater is the main water resource for various purposes such as drinking, agriculture and industrial. To evaluate the hydrochemical characteristics of groundwater and suitability for drinking, irrigation and industrial purposes, seventy-seven samples were collected and analyzed for various ions. Results show that, groundwater in the study area is mainly hard to very hard, and slightly alkaline-fresh to brackish in nature. According to the hydrochemistry diagrams, the main groundwater types are Ca, Mg-HCO 3 , Na-HCO 3 and Na-Cl. Calculation of mineral saturation index indicate that the groundwater samples are saturated with respect to carbonate minerals and under-saturated with respect to sulfate minerals such as gypsum and anhydride. The mineral weathering, mixing, ion exchange and anthropogenic activity are the dominant hydrogeochemical natural processes. Results of investigating the quality of heavy metals and calculating the heavy metal index indicated that the groundwater of study area is not contaminated with heavy metals. In this research, the various indices were used to determine the quality of groundwater for various uses. Calculate the indices and comparison results with the WHO standards to determine the quality of groundwater for various uses indicated that the most of the groundwater in study area is chemically suitable for drinking, industrial and agricultural uses.

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