Stability and environmental geochemical profile of toxic heavy metals in soils around a crude oil refinery

Soil samples were taken near oil refinery activities, bulk and fractionated heavy metal contents, as well as other physico-chemieal characteristics were measured. The reported results indicate that the enrichment factors of the measured heavy metals were 3.9, 1.8, 1.3, 23.7 and 52.5 for lead, nickel, zinc, cadmium and mercury, respectively. The samples can be considered to be extremely contaminated with respect to mercury, strongly contaminated with respect to cadmium, moderately to uncontaminated with respect to lead and nickel, and uncontaminated with respect to zinc. The distribution of the measured heavy metals is affected by pH, clay content, total dissolved solids, cation exchange capacity, organic matter content and carbonate content. Lead, nickel and zinc are mainly associated with the residual fraction and are relatively immobile, and therefore they are unlikely to pose a threat to the ecosystem under natural environmental conditions.