Assessment of heavy metal pollution of groundwater at the upper stream of Wadi Ranyah, Saudi Arabia, using multivariate statistical approach

Abstract

Seventy-seven groundwater samples from Wadi Ranyah, Saudi Arabia, were analyzed to assess their physical and chemical properties. Initially, the physiochemical parameters were compared to the World Health Organization (WHO) standards and studied with Durov and Chadha diagrams. Multivariate statistical indices, such as the saturation index (SI), chloro-alkaline indices (CAI), Gibbs ratios, heavy metals pollution and evaluation indices (HPI and HEI), and the hierarchical cluster analysis (HCA), were used to identify the sources of water pollution. Durov’s diagram showed that Ca and HCO₃ ions were the dominant, and forward ion exchange was the main hydrochemical reaction. The SI results showed that the water samples were oversaturated with carbonates and in equilibrium with evaporite minerals, except for halite and sylvite. The CAI was positive in 83% of the samples, indicating forward ion exchange and Ca dominance. The Gibbs diagram showed that rock weathering (carbonate dissolution) was the dominant process controlling water chemistry. The levels of Cd, Cr, Pb, As, Hg, Li, and Mo exceeded the WHO limits in all samples, while Ni and Co exceeded the limits in 51% and 65% of the samples, respectively. The HPI and HEI results showed that the water samples were highly contaminated with heavy metals and unsuitable for consumption. The HCA showed that the main factors affecting the water salinity were dissolved carbonates, gypsum, the major ions, and some heavy metals. The HCA also showed that the main variables contributing to water salinity were dissolved carbonates, gypsum, major ions, and heavy metals. The study concluded that the water samples are not suitable for drinking and other domestic uses, and groundwater treatment measures are recommended to protect the population from serious health risks.