Document Type : Original Manuscript
Authors
1 Department of Hydrology and Environmental Geology, Earth Sciences Faculty, Shahrood University of Technology, Shahrood, Iran.
2 Regional Water Company of Golestan Province, Gorgan, Iran.
Abstract
The Ziarat River is one of the tributaries of the Qarah-su catchment, and a part of this river flows through Gorgan City. In order to investigate the environmental hydrogeochemistry of the river, 11 water samples were collected. Physicochemical parameters, the concentrations of major ions and metals, as well as the biological parameters were analyzed. The obtained results show that pH and EC of the water samples vary from 7.2 to 7.9, and from 701 to 1422 μS/cm, respectively. The highest pH and EC values were observed near the discharging point of cowshed effluents and the Ziarat hot spring, respectively. On the basis of hydrogeochemical studies, the chemical composition of water samples is mainly controlled by the dissolution process. The water type changed from Ca-SO4 in upstream to Na-Cl in downstream, probably because of natural and anthropogenic factors. Regarding the major ion concentrations, all water samples are in the acceptable range for drinking usage. Based on the Wilcox diagram, and regarding the calculated residual sodium carbonate and sodium percentage values, the studied water samples are suitable for drinking and agricultural purposes; however, regarding the values of magnesium hazard index, most of the samples are not suitable for agricultural usage. Metal pollution indices show that studied samples are highly polluted, especially those samples which were collected at the wastewater discharging points. The values of dissolved oxygen in all samples are in the permissible limits. However, in some stations, BOD and COD levels are higher than permissible values, and the highest amount of these parameters is observed near the discharging point of cowshed and agricultural effluents. All water samples are microbially polluted, and the lowest microbial pollution is observed in upstream stations. The values of Water Quality Indices indicate that all studied samples are classified as low and very low quality.
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