Evaluation of heavy metal contamination and groundwater quality along the Red Sea coast, southern Saudi Arabia

Highlights: • To evaluate the heavy metal contamination and groundwater quality in southern Saudi Arabia, 105 samples were collected. • The maximum values of As, Mn, Cr, Ni, Se, and Zn were above the permissible limits for drinking water purposes. • The major cations and anions followed the orders of Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and Cl⁻ > SO₄²⁻ > HCO₃⁻ > NO₃⁻ > F⁻, respectively. • 20 to 52% of the groundwater samples were suitable for agricultural and domestic purposes. • The unsuitable samples were distributed mostly in the western part along the Red Sea coast. To evaluate the heavy metal contamination and groundwater quality in southern Saudi Arabia, 105 groundwater samples were analyzed for EC, pH, TDS, major ions (NO₃⁻, Cl⁻, HCO₃⁻, SO₄²⁻, F⁻, Ca²⁺, Mg²⁺, Na⁺, and K⁺), and heavy metals (Fe, Li, As, B, Al, Cr, Cu, Mo, Ni, Se, Sr, V, Zn, and Mn). Groundwater quality index (GWQI), degree of contamination (C_d), heavy metal pollution index (HPI), ecological risks of heavy metals (ERI), salinity hazard (EC), sodium adsorption ratio (SAR), sodium percentage (Na%), and Kelly's ratio (KR) were calculated and compared, and multivariate statistical techniques were applied. The results revealed that the major cations and anions followed the orders of Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and Cl⁻ > SO₄²⁻ > HCO₃⁻ > NO₃⁻ > F⁻, respectively. The maximum values of As, Mn, Cr, Ni, Se, and Zn were above the permissible limits for drinking water purposes. Pollution indices indicated that 20 to 52% of the groundwater samples were suitable for agricultural and domestic purposes. The unsuitable samples were distributed mostly in the western part along the Red Sea coast. Multivariate statistical analyses revealed that the dissolution of halite and gypsum (in sabkha deposits), carbonates, and the agricultural activities were the possible sources of the major cations and anions, and heavy metals in the study area.