| چکیده انگلیسی مقاله |
In recent years, Hamzeh city, located to the east of Dezful, has faced increasing nitrate contamination in drinking water wells, with landfill leachate and urban wastewater proposed as the main potential sources of pollution. To investigate the origin of nitrate and the influence of geological factors, groundwater samples were collected from ten pumping wells during January 2018, August 2018, and November 2018. The samples were analyzed for major ions and nitrate concentrations. Statistical analysis, factor analysis, saturation indices, Piper diagrams, and electrical conductivity (EC) and chloride contour maps identified halite dissolution as the most significant geological process controlling groundwater hydrochemistry. Based on hierarchical cluster analysis and self-organizing maps (SOM), the samples were classified into three distinct groups. Group 1, located in the northern part of the study area, is characterized by the lowest EC values (approximately 500 µmho/cm) and dissolved solids. Group 3, situated in the southern part of the area, exhibits the highest EC values (approximately 1000 µmho/cm) and dissolved solids, while Group 2, located in the central part of the study area, shows intermediate characteristics. The progressive increase in EC from Group 1 to Group 3 is attributed to halite dissolution within the Aghajari and Lahbari formations. Previous analyses showed no significant correlation between nitrate and other hydrochemical variables. Nitrate contour maps indicate that the highest nitrate concentrations occur in the southern part of the city, coinciding with the direction of groundwater flow. Additionally, elevated nitrate concentrations were observed in agricultural areas at the end of the growing season. Therefore, urban wastewater is identified as the primary source, and agricultural activities as a secondary source of nitrate contamination in the study area, while no significant impact of the landfill on groundwater quality was detected. Overall, the results demonstrate the effectiveness of the SOM approach in clustering groundwater samples and identifying the dominant factors affecting groundwater quality. |
