Hydrochemical Assessment of Groundwater from the Harrat Khyber Flood Basalts, Northwest Saudi Arabia

The present study was carried out in the Harrat Khyber region of the Madinah province in Western Saudi Arabia. The objective of the study was to determine the main factors affecting groundwater chemistry and assess the impact of groundwater quality on human health with respect to nitrate, fluoride, and heavy metals (arsenic, chromium, copper, nickel, selenium, and zinc). Hydrochemical data for 70 groundwater samples from dug wells and bore wells from Harrat Khyber were interpreted to achieve the research objective. The groundwater chemistry is influenced by ion-exchange and the evaporation process. A wide variation in the concentration of various major ions is observed primarily due to the varied nature of the aquifer system which includes the unconsolidated wadi deposits, weathered-fractured basaltic aquifer system, and subbasaltic sedimentary aquifer system. The total hazard quotient (THQ) with respect to NO3 and F was determined. Although the F values are well within the limits of human consumption in water prescribed by WHO, the values of NO3 exceed the allowable limits in 50% of the groundwater samples. The average THQ values are 2.16, 2.92, and 2.34 for adults, children, and infants, respectively, which makes the water unsafe for human consumption. Six heavy metals (arsenic, chromium, copper, nickel, selenium, and zinc) were used to calculate the heavy-metal contamination index (HCI). The average HCI value is 19.505. Overall HCI calculation shows that the groundwater is unpolluted with respect to heavy metals. The heavy metals in water are mainly of geogenic origin.

Automated summary

The present study aimed to investigate the groundwater chemistry and its impact on human health in the Harrat Khyber region of Western Saudi Arabia. The results showed that the groundwater chemistry was influenced by ion-exchange and evaporation processes, and there was a wide variation in the concentration of major ions. Additionally, heavy metals such as arsenic, chromium, copper, nickel, selenium, and zinc were found to be mainly of geogenic origin, causing minimal contamination in the groundwater. However, excessive levels of nitrate were observed, making the water unsafe for human consumption.