Rivers are considered to be the most important sources of fresh water for drinking, agricultural and industrial purposes, but the increase in mining, agricultural and urban development activities can affect the quality of these resources. The Saridareh River is located in the east of East Azerbaijan Province and in an area with high mineral potential and plays an important role in providing drinking and agricultural water in the region. The aim of this study was to evaluate the water quality of the Saridareh River for drinking and agricultural purposes and also to investigate the origin of water chemical changes. In order to achieve this goal, sampling was carried out from 14 points along the river during two dry and wet periods from August 2025 to March 2026. The measured parameters included heavy metals such as arsenic, lead and iron and physicochemical parameters (major ions and trace elements). Water quality was also evaluated using common irrigation indices, Piper and Wilcox diagrams and Pearson correlation analysis. The results showed that the average concentrations of As, Pb and Fe were 1.40, 6.8 and 0.017 μg/l respectively and except for a few stations with a relative increase in Pb, all other values were below the permissible limits of the World Health Organization. The pH values were measured between 7.77 and 8.33, TDS between 148 and 330 mg/l and EC between 297 and 660 μS/cm, which indicate good water quality and the prevalence of weak alkaline conditions. The dominant hydrochemical facies were Ca-HCO3 and Ca-Mg-HCO3, and the weathering process of carbonate rocks was identified as the most important factor controlling water chemistry. The results of the correlation analysis also showed a significant relationship between As and SO42-, EC and TDS, which confirms the terrestrial origin of this element. Agricultural indices, Wilcox plot indicated that all samples were in the C2-S1 class and the water was suitable for irrigation. Also, the river water is mainly sediment-forming and does not pose a serious risk of corrosion for industrial uses. Overall, the water quality of the Saridareh River was assessed as desirable for drinking, agricultural, and industrial uses, and geological processes and rock weathering were identified as the most important factors controlling the chemical composition of the river water.

Introduction
Rivers are considered to be the most important sources of fresh water, which play a fundamental role in providing drinking water, agriculture, and maintaining the stability of natural ecosystems. However, the development of human activities, the expansion of urbanization, the increase in mining and agricultural exploitation, as well as the natural processes of rock weathering can affect the quality of these resources. The Saridareh River is located in the city of Kalybar and, due to its location within the Arasbaran metallogenic belt and proximity to areas with mineral potential, is of particular importance from the perspective of assessing water quality and determining the origin of dissolved elements. The aim of this study was to investigate the water quality of the Saridareh River for drinking, agricultural, and industrial uses, as well as to analyze the geochemical origin of dissolved elements and ions in the water of this river.

Materials and methods
In order to achieve the research objectives, water sampling was carried out from 14 stations along the river during different hydrological periods. Physicochemical parameters including pH, EC, TDS, TH, HCO3ˉ, Clˉ, SO42- and NO3ˉ were measured. Also, the concentration of selected elements including arsenic, lead, iron, zinc, barium and other elements were determined using ICP-MS. Common drinking, agricultural and industrial indicators were used to assess water quality and the relationships between parameters were examined through Pearson correlation analysis. In addition, the hydrochemical facies of the water was assessed using the Piper diagram and the irrigability was assessed using the Wilcox diagram and USSL classification.

Results and discussion
The results showed that the average arsenic concentration was 1.40 μg/l and was lower than the World Health Organization permissible limit (10 μg/l) at all stations. Lead concentrations ranged from 0.05 to 13.43 μg/l and exceeded the drinking water guideline at several stations, which is likely due to the weathering effects of the mineral units and activities related to mineralization in the region. The average iron concentration was also much lower than the drinking water limit, indicating adequate water quality in this regard. The sulfate, chloride, and nitrate values in all samples were below standard limits, indicating limited impact of human pollutant sources on river water quality. The pH values ranged from 7.77 to 8.33 with an average of about 8.06, indicating slightly alkaline water conditions. Electrical conductivity ranged from 297 to 660 μS/cm and TDS ranged from 148 to 330 mg/l, indicating that the water is sweet and the risk of salinity is low. The results of the correlation analysis showed that arsenic has a positive and significant correlation with sulfate, EC and TDS, indicating a common terrane origin and the role of weathering of sulfide minerals in the release of this element. Also, sulfate showed a strong and significant correlation with EC and TDS, confirming its role in controlling the ionic load of water. The study of water quality for agricultural purposes showed that all samples fall into the C2-S1 class, which indicates water with moderate salinity and low sodium risk. Low levels of sodium, chloride and sulfate indicate that the water is suitable for irrigation of most crops and horticultural crops in the region. The results of the Wilcox plot also showed that most samples are in the "excellent to good" and "good to acceptable" ranges and that long-term use of this water does not pose a significant risk in terms of soil salinization or sodium. From an industrial perspective, 13 stations had sedimentation properties and only one station had corrosive properties, indicating that the river water mainly tends to form calcium carbonate deposits in industrial facilities.

Conclusion
According to the Piper diagram, the dominant facies of the river water are Ca-HCO3 and Ca-Mg-HCO3, indicating that the water chemistry is controlled by the weathering process of carbonate rocks and the dissolution of minerals containing calcium and magnesium. Overall, the results of this study indicate that the water quality of the Saridareh River is suitable for drinking and agricultural purposes, and natural geological processes and rock weathering are the most important factors controlling the chemical composition of the water. However, the observation of relatively high concentrations of lead at some stations highlights the need for continuous monitoring of this element and assessment of the possible effects of mining activities in the catchment area.