Shahid Beheshti University Researches in Earth Sciences 2008-8299 11 4 2021 01 20 Using geochemical techniques to identify the origin of ions and processes controlling groundwater quality of Shahrood aquifer Using geochemical techniques to identify the origin of ions and processes controlling groundwater quality of Shahrood aquifer 181 196 97447 10.52547/esrj.11.4.181 FA Hadi Jafari Department of Geology, Faculty of Earth Sciences, Shahrood university of Technology, Shahrood, Iran Zahra Boosalik Department of Geology, Faculty of Earth Sciences, Shahrood university of Technology, Shahrood, Iran Journal Article 2019 03 08 Introduction<br />Groundwater is in contact with different materials and undergoes several reactions, in its flow way, from the recharge point to the discharge point. In this path, some of the materials are dissolved in water and some others are deposited in it, and the water quality changes in the aquifer. Determining and identifying the factors affecting water quality, can be an effective step towards the quality management of aquifers. In the north of Shahrood aquifer, the groundwater type is bicarbonate with a good quality and its EC is about 671 μs/cm, while water quality decreases gradually in the southward direction and eventually it changes to saline water which is from sodium chloride type and the amount of EC (μs/cm) is 11210. The present study was carried out to identify the origin of ions and important processes controlling water quality in Shahrood aquifer. Results and Discussion<br />According to the geology and lithology situation of Shahrood aquifer, the most probable hypothesis for the groundwater salinity in this aquifer is the dissolution of evaporative formations’ dispersion in the eastern and southern parts of the aquifer. This is consistent with the high salinity areas of the aquifer. However, there are evaporative formations in the southwest parts of the aquifer too, even though the salinity of samples taken from these parts is low. Based on the results of this study, halite and gypsum dissolution processes and precipitation of calcite and dolomite and direct and reverse cation exchanges are the most important processes for controlling water quality in Shahrood aquifer. The creation of the water divide line in the eastern and southeastern parts of the region has led to changes in the general trend of groundwater flow in the aquifer. The general direction of groundwater flow in the Shahroud aquifer is from the northern, eastern and southeast parts to the central, western, and southwest parts. But the operation of groundwater divide line, changed the flow direction to eastward around the village of Royan. This hydrogeological complexity has also affected the aquifer's groundwater quality. In fact, the groundwater divide line has prevented the penetration of saline water from the eastern and southeastern parts to the central and western parts of the aquifer. This has caused these saline water masses to be non-effective on the hydrochemistry of the Shahrood aquifer.<br />Conclusion<br />Based on the results of this study, halite and gypsum dissolution processes and precipitation of calcite and dolomite and direct and reverse cation exchanges are the most important processes for controlling water quality in Shahrood aquifer. The groundwater divide line, has prevented the penetration of saline water from the eastern and southeastern parts to the central and western parts of the aquifer. This has caused these saline water masses to be non-effective on the hydrochemistry of west the Shahrood aquifer. Introduction<br />Groundwater is in contact with different materials and undergoes several reactions, in its flow way, from the recharge point to the discharge point. In this path, some of the materials are dissolved in water and some others are deposited in it, and the water quality changes in the aquifer. Determining and identifying the factors affecting water quality, can be an effective step towards the quality management of aquifers. In the north of Shahrood aquifer, the groundwater type is bicarbonate with a good quality and its EC is about 671 μs/cm, while water quality decreases gradually in the southward direction and eventually it changes to saline water which is from sodium chloride type and the amount of EC (μs/cm) is 11210. The present study was carried out to identify the origin of ions and important processes controlling water quality in Shahrood aquifer. Results and Discussion<br />According to the geology and lithology situation of Shahrood aquifer, the most probable hypothesis for the groundwater salinity in this aquifer is the dissolution of evaporative formations’ dispersion in the eastern and southern parts of the aquifer. This is consistent with the high salinity areas of the aquifer. However, there are evaporative formations in the southwest parts of the aquifer too, even though the salinity of samples taken from these parts is low. Based on the results of this study, halite and gypsum dissolution processes and precipitation of calcite and dolomite and direct and reverse cation exchanges are the most important processes for controlling water quality in Shahrood aquifer. The creation of the water divide line in the eastern and southeastern parts of the region has led to changes in the general trend of groundwater flow in the aquifer. The general direction of groundwater flow in the Shahroud aquifer is from the northern, eastern and southeast parts to the central, western, and southwest parts. But the operation of groundwater divide line, changed the flow direction to eastward around the village of Royan. This hydrogeological complexity has also affected the aquifer's groundwater quality. In fact, the groundwater divide line has prevented the penetration of saline water from the eastern and southeastern parts to the central and western parts of the aquifer. This has caused these saline water masses to be non-effective on the hydrochemistry of the Shahrood aquifer.<br />Conclusion<br />Based on the results of this study, halite and gypsum dissolution processes and precipitation of calcite and dolomite and direct and reverse cation exchanges are the most important processes for controlling water quality in Shahrood aquifer. The groundwater divide line, has prevented the penetration of saline water from the eastern and southeastern parts to the central and western parts of the aquifer. This has caused these saline water masses to be non-effective on the hydrochemistry of west the Shahrood aquifer. https://esrj.sbu.ac.ir/article_97447_dc0460bea910d5199aaad8ce3a556b8a.pdf