Risk assessment through evaluation of potentially toxic metals in the surface soils of the Qassim area, Central Saudi Arabia

Metal pollution is an increasing environmental problem worldwide, especially in regions undergoing rapid development. The present work highlights the extent of metal pollution in the central part of Saudi Arabia, which is currently experiencing significant agricultural development. The study determined concentrations of Hg, Cd, Zn, As, Mo, Cu, Pb and Cr in surface soils, assessing the level of pollution and potential ecological risks using soil quality guidelines, the geo-accumulation index (I_geo), the Hakanson potential ecological risk index (RI) and standard statistical analysis methods. Overall, the mean potential ecological risk values of metals in the surveyed soils display the following decreasing trend: Hg<Cd<Pb<As<Cu<Zn<Mo<Cr. The potential ecological risks associated with the eight investigated metals in the study area were high for Hg and Cd, and ranged from considerable too low for the rest of the analysed metals. The results also showed that surface soils in the study area are heavily affected by agricultural activities, municipal waste, local industries and quarries. These anthropogenic activities may, therefore, pose a risk to soil and water resources, and have the potential to change the physio-chemical characteristics of the associated ecosystem.