Urbanization-Induced Groundwater Contamination in Barjisiyah Area, Southern Iraq: Hydrochemical, Isotopic, and Microbial Assessment

Abstract

Recent urbanization and overexploitation have significantly degraded groundwater quality in the shallow unconfined aquifer in Barjisiyah. The study area is located within the discharge area and is exposed to natural salinization from the underlying layer and anthropogenic sources with limited rainfall recharge. Six groundwater samples have been collected from the unconfined aquifer across urbanized zones. Total Dissolved Solids reach an extremely high level of 22,200 mg/L, with a wide range of major ion concentrations.  Hydrochemical facies are dominated by sodium-chloride and calcium-chloride, confirming advanced mineralization. The distinct geochemical and isotopic contents observed in the shallow aquifer suggest a conceptual mechanism of upward leakage from the underlying semi-confined layer. The evaporitic minerals are dominant, with no halite dissolution, sulfate mineral saturation, and supersaturation of carbonate minerals. The isotopic signatures have been plotted below the Global and regional Meteoric Water Lines, with recognized negative values of d-excess, providing dual insights into the hydrogeological processes governing the aquifer. Isotopic signatures suggest infiltration of evaporated water into the aquifer and upward saline mixing. The major finding is that the microbial indicator counts exceed the levels set by global safety standards, with E. coli reaching 400 CFU/mL. Groundwater quality deterioration may increasingly limit agricultural suitability over time.