Lithological influence on water quality evolution: A case study of the Zuzan Plain, northeast Iran

This study investigates the influence of lithological characteristics on the evolution of water quality in the Zuzan Plain, Northeast Iran, a region characterized by limited water resources. A total of ۲۳ water samples were collected from various sources across the area. Physical parameters, including acidity (between ۷.۲ and ۸.۷), dissolved solids (۱۱۸۰–۷۴۱۵ mg/l), electrical conductivity (ranging from ۲۱۰۰ to ۱۲,۲۱۰ microsiemens/cm), and salinity, were measured on-site using an Extech model multimeter. Water hardness (۱۰۰–۱۹۶۰ mg/lCaCO۳) was analyzed at the laboratory. Statistics software was used to analyze the correlations between elements and their relationship with the region’s lithology. Water facies were identified using RockWorks ۱۶ software. The Piper and Stiff diagrams revealed that most samples exhibited sodic facies with chloride type, except for two samples, which displayed sodic facies with sulfate type. Furthermore, the Gibbs diagram was employed to distinguish the dominant hydrogeochemical processes, indicating that both evaporation and rock-water interactions strongly influence the groundwater composition. To better understand spatial controls, a groundwater flow direction map was prepared, clarifiying the distribution of water facies in relation to regional hydrogeology. Cluster analysis and principal component analysis of the water samples revealed two main components influencing the source variations. The presence of acidic igneous units, limestone, sandstone, conglomerate, siltstone, and shale in the region suggests their significant role in controlling the chemical composition of the water. Limestone, due to its higher solubility, is identified as the primary regulator of water quality in the Zuzan Plain, while igneous and sedimentary rocks exert secondary influences.

کلیدواژه ها:

water resources ، lithology ، Sedimentation ، Zuzan plain ، Iran