Hydrogeochemical Assessment of Groundwater Quality in Basaltic and Alluvial Aquifers, Al Madinah Al-Munawwarah, Saudi Arabia

The assessment of groundwater quality in selected wells of Al Madinah El-Munawwarah region, Saudi Arabia, employed geochemical methods to identify main controlling factors. Key physicochemical parameters, including total dissolved solids (TDS), electrical conductivity (EC), pH, total hardness (TH), and major ion concentrations, were evaluated. The results indicate that several parameters exceed permissible limits established by Gulf and international standards, reflecting highly saline conditions that could adversely affect drinking water safety and agricultural practices. Elevated nitrate levels and other contaminants suggest combined influences of geological processes and anthropogenic activities such as mineral leaching and agricultural runoff. Correlations among various ions reveal complex interactions driven by both natural and human factors, notably a moderate correlation between nitrate and sewage indicators in the basaltic aquifer. Heavy metals in groundwater were classified into two groups: those within permissible limits (Ag, Ba, Be, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Sb, and U) and those exceeding recommended limits (Zn, Al, As, Se, and Tl). Elevated metal concentrations are primarily attributed to water–rock interactions and the fertilizer use in surrounding agricultural areas. These findings highlight the urgent need for continuous monitoring and proactive groundwater to ensure sustainable and safe use of water resources.