Geostatistical and pollution index-based approach for assessing heavy metal pollution in the Cambro-Ordovician Saq Aquifer in Central Saudi Arabia

This study was carried out in Al-Qassim province of Saudi Arabia with the objective of assessing the heavy metal contamination in groundwater. The Saq sandstone aquifer is the main source of water supply in Al Qassim province. Twenty-one groundwater samples were collected from the area and were analyzed for heavy metals (HMs) using the ICP-MS technique. The analyzed elements include As, Ba, Cd, Cr, Cu, Mn, Ni and Zn. The concentration of these elements were compared with the WHO groundwater quality standard. Principal Component Analysis (PCA) was carried out to determine the elements representing the maximum variation in the analyzed data. Pollution indices such as Heavy-metal Pollution Index (HPI) and Heavy-metal Contamination Index (HCI) were calculated to determine the impact of HM on groundwater quality. Three principal components (PCs) accounting for 69.57% of the total data variability was extracted. The mean HPI and HCI values of the samples were 3.57 and 5.66, respectively, which shows that the groundwater is uncontaminated with respect to HM. The groundwater appears mineralized as evident from the EC values, but no threat of groundwater pollution from HMs was found. The low concentration of the HM also indicated that they were mostly of geogenic origin and the impact of agricultural activities on groundwater was absent.