Coastal aquifers are at threat of salinization in most parts of the world. This work investigated the seasonal hydrochemical evolution of coastal groundwater resources in Urmia plain, NW Iran. Two recently proposed methods have been used to comparison, recognize and understand the temporal and spatial evolution of saltwater intrusion in a coastal alluvial aquifer. The study takes into account that saltwater intrusion is a dynamic process, and that seasonal variations in the balance of the aquifer cause changes in groundwater chemistry. Pattern diagrams, which constitute the outcome of several hydrochemical processes, have traditionally been used to characterize vulnerability to sea/ saltwater intrusion. However, the formats of such diagrams do not facilitate the geospatial analysis of groundwater quality, thus limiting the ability of spatio-temporal mapping and monitoring. This deficiency calls for methodologies which can translate information from some diagrams such Piper diagram into a format that can be mapped spatially.Distribution of groundwater chemistry types in Urmia plain based on modified Piper diagram using GQI Piper(mix) and GQI Piper(dom) indices that Mixed Ca-Mg-Cl and Ca-HCO 3 are the dominant water types in the wet and dry seasons, respectively. In this study, a groundwater quality index specific to seawater intrusion (GQI SWI ) was used to check its efficiency for the groundwater samples affected by Urmia hypersaline Lake, Iran. Analysis of the main processes, by means of the Hydrochemical Facies Evolution Diagram (HFE-Diagram), provides essential knowledge about the main hydrochemical processes. Subsequently, analysis of the spatial distribution of hydrochemical facies using heatmaps helps to identify the general state of the aquifer with respect to saltwater intrusion during different sampling periods. The HFE-D results appear to be very successful for differentiating variations through time in the salinization processes caused by saltwater intrusion into the aquifer, distinguishing the phase of saltwater intrusion from the phase of recovery, and their respective evolutions. Both GQI and HFE-D methods show that hydrochemical variations can be read in terms of the pattern of saltwater intrusion and groundwater quality status. But generally, in this case (i.e. saltwater and not seawater intrusion) the HFE-D method was presented better efficiency than GQI method (including GQI Piper and GQI SWI ).
Study of the 59 groundwater samples from Lenjanat area, central Iran, was carried out in order to assess their chemical compositions and suitability for drinking and agricultural purposes. Based on Gibbs' diagram, weathering of rocks and evaporation were found to be the dominant processes in the ion concentration of the water samples. The saturation index calculated through geochemical modeling indicates a suitable chemical environment for anhydrite, aragonite, calcite, dolomite, fluorite, and gypsum dissolution in both wet and dry seasons. All samples have the SO 4 2-? HCO 3 -more than 5 meq/l indicating that in addition to calcite and dolomite, dissolution of gypsum is the probable process in this plain. Assessment of the concentration of Mg 2? ? Ca 2? proportion to SO 4 2-? HCO 3 -demonstrates that the advanced direct and reverse ion exchange between groundwater and surrounding environment has occurred. The Chadha diagram indicates that the amount of earthalkali parameters is more than alkali ones and by considering the high value of strong acids, the dominant hydrochemical facies in both wet and dry seasons are Ca 2? -Mg 2? -Cl --SO 4 2-. According to pollution index, in the selected time domain, all samples are in safe conditions. Calculation of entropy weighted water quality index for groundwater samples demonstrates that in the wet and dry seasons, over 57 and 42 % of the samples are in the range of ''excellent'' to ''medium'' quality, respectively. The values of SI, RSC, SSP, SAR, KR, PI, MAR, and CI show that 90 and 85 % of the samples in wet and dry seasons have the good quality for agricultural purposes.
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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