The chemical analysis of 129 groundwater samples in the Kadkan area, Khorasan-e-Razavi Province, NE of Iran was evaluated to determine the hydrochemical processes, assessment of groundwater quality for irrigation purposes, corrosiveness, and scaling potential of the groundwater. Accordingly, the suitability of groundwater for irrigation was evaluated based on the sodium adsorption ratio, residual sodium carbonate, sodium percent, salinity hazard, and US Salinity Laboratory hazard diagram. Based on the electrical conductivity and sodium adsorption ratio, the dominant classes are C3-S1, C3-S2, C2-S1, and C4-S2. According to the Wilcox plot, about 50 % of the samples fall in the "Excellent to Good" and "Good to Permissible" classes. Besides, the Langelier saturation index, Ryznar stability index (RSI), Larson-Skold index, and Puckorius scaling index were evaluated for assessing the corrosiveness and scaling potential of the groundwater. Corrosiveness and scaling indices stated that the majority of samples are classified into "Aggressive" and "Very Aggressive" category. In addition, chloride and sulfate interfere in 90 % of the samples. Assessment of hydrochemical characteristics indicates Na-Mg-Cl as the predominant hydrochemical type. Spatial distribution of hydrochemical parameters indicates that hydrochemical processes are influenced by geology and hydrogeology of Kadkan aquifer. The Gibbs plots gave an indication that groundwater chemistry in this area may have acquired the chemistry mainly from evaporation and mineral precipitation. Grouping the samples based on Q-mode hierarchical cluster analysis helped to more separation of similar samples. The R-mode HCA grouped analyzed parameters into two groups based on similarity of hydrochemical characteristics. As a result, the samples collected in northern and southern parts of the study area show the best quality (i.e., lowest salinity) for some purposes such as irrigation and drinking.

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Hydrochemical investigations were carried out in the Kadkan area, northeastern Iran, to assess the chemical composition of groundwater. A total of 131 groundwater samples were collected and analyzed for major cations and anions. The domination of cations and anions was in the order of Na2-in anions. The groundwater is under-saturated with respect to anhydrate, aragonite, calcite, dolomite, gypsum, and CO 2 . In this investigation, multivariate statistical techniques were used to identify and understand hydrochemical association and processes leading to the variability of groundwater quality. Factor analysis was applied to all groundwater samples and 11 variables. This analysis revealed that three main factors affecting the groundwater chemistry can be distinguished in this plain. Factor 1 includes the major ions in aqueous solution and accounts for 51.68 % of the total variance. Factor 2 accounts for 15.39 % of total variance and includes the parameters pH, Ca, and CO 3 in the plain, suggesting that the geology of some parts of the area is primarily limestone. Factor 3 includes the parameters Mg and HCO 3 and accounts for 11.63 % of the total variance. These parameters have a geological source. The hydrochemical processes of groundwater in the Kadkan aquifer are mainly influenced by the major ions, degree of dissolution of NaCl-bearing minerals, and geology.