Heavy metal pollution in well water and ecological risk assessment for the surrounding soil

The present study aims to evaluate the level of heavy metal contamination of well water and soil in the Al-Quwayiyah governorate, Kingdom of Saudi Arabia (KSA). The samples for the study were selected from 10 different sites and then tested for the presence of chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), lead (Pb), and iron (Fe). The physicochemical properties of well water and soil samples were investigated. Multivariate analyses including the correlation matrix (CM), principal component analysis and analysis of variance were used to specify the correlation between and the impact of heavy metals contamination of soil on well water. The potential ecological risk was assessed using the sediment quality guidelines (SQGs), enrichment factor (EF), geo-accumulation index (I-geo), contamination factor (C-f), and the degree of contamination (C-d) to identify the sources of heavy metals in the soil samples. Two ratios prescribed by the SQG's were used. The first was "effect range low (ERL) to effect range median (ERM) values" and the second was "threshold effect level (TEL) to probable effect level (PEL)". The results revealed that these ratios did not exceed the United States Environmental Protection Agency (USEPA) guidelines. The EF values of the soil samples showed minimal to deficient enrichment with Cr, Ni, Cu, Zn and As, and extremely low enrichment with Cd and Pb. The data obtained demonstrated that all the sites were polluted with very low levels of these heavy metals. The results strongly and positively correlated the metals in well water with these in soil and clarified that all metals were of a lithogenic origin.