Evaluation of Hydrogeochemical Characteristics and Evolutionary Process of Groundwater in Jajarm Plain, Northeastern Iran

Abstract

Jajarm Plain in the province of North Khorasan is located, in terms of structural zoning, in the north of the central desert basin and in the south of the Alborz mountain range. The aim of this study was to investigate the factors influencing the evolutionary process of groundwater resources and hydrogeochemical characteristics of water resources of Jajarm plain. To achieve this goal, 20 water samples were taken from the plain wells and physical parameters such as pH, TDS, EC, and salinity were measured in situ using multimeter. In addition, the chemical properties of the surface water entering the plain were also evaluated. The hydrogeochemical analysis was carried out in the laboratory through induction plasma method, the statistical analysis and modeling were performed in Chemistry and AqQA software environment. According to the Piper chart, most of the groundwater in this plain was a part of the sodic and chloride type facies, and in some examples, the sodic facies and the sulfate type. Chemical analysis of water entering the aquifer of Jajarm plain showed that the sources of ions entering the plain of Jajarm were affected by the lithology of rocks and sediments that were exposed to weathering for a long time; hence, as the plain waters, due to the passage of the detrital evaporation formations of the third period (marl, salt gypsum, and marl limestone formation), have dissolved them and increased the ratio of Cl+ SO4> HCO. The results showed that the presence of rocks and minerals of carbonate (calcite), sulfate (gypsum) and silicate (tuff and detrital igneous rock) in the water passage has caused the scenarios of Ca>CO3 and Ca+Mg>CO3. Based on the calculations, it was found that the evolutionary trend of water samples in this plain, if not properly managed, will lead to the formation of SO₄>Mg ratio, which will probably lead to the formation of sodium carbonates and halites in the future, and also eventually rising EC and the emergence of saline in the Jajarm plain in the future.

Keywords

• geology
• hydrogeochemistry
• plain
• water resources