Mohammad Ebrahimi, Mohammad Javad Nematollahi, Alireza Moradian, Sadegh Adineh, Rasoul Esmaeili
Department of Geology, Faculty of Sciences, University of Zanjan, Zanjan, Iran
Department of Earth Sciences, College of Sciences, Shiraz University, Shiraz, Iran
Department of Earth Sciences, College of Sciences, Ferdowsi University, Mashhad, Iran
Key words: Hydrogeochemistry, Irrigation water quality, Surface water, Gilan province.
Surface water in Gilan province is assessed in order to determine its hydrogeochemistry and irrigation water quality using 55 water samples. In this regard, concentration of major ions and physicochemical parameters including , , , , , , and pH, EC and TDS were determined. The average content of the major cations and anions follow as: and , respectively. Hydrogeochemical composition of surface water is a mixture of water types including , mixed and . Nonetheless, themajority of the samples has water type. Hence, alkaline earths and strong acid anions exceed alkalis and weak acid anions, respectively. Based on Gibbs diagrams and ionic ratios, weathering of silicate minerals is the main process controlling the surface water chemistry. Saturation indices (SIs) indicate that dissolution of carbonate minerals also plays an important role in regulating the surface water chemistry. Although sodium percentage (Na%), sodium adsorption ratio (SAR), electrical conductivity (EC), total dissolved solids (TDS) and permeability index (PI) in most of the samples are below the standard, nonetheless, residual sodium carbonate (RSC) and Total hardness (TH) indicate significant irrigation water unsuitability and hence thenecessity for caution and future study.
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