Assessing the extent of heavy metal contamination in crude oil-impacted soils in the Niger Delta, Nigeria using geochemical indicators

Abstract

The study presents heavy metal (HM) [copper-Cu, chromium-Cr, nickel-Ni, vanadium-V, lead-Pb, zinc-Zn and iron-Fe] contamination in genuine crude oil-impacted soils and pristine (control) soils. HM concentrations were measured using inductively coupled plasma (ICP). Using soil Contamination factor, Enrichment factor, Pollution load index and Geo-accumulation index, the extent of heavy metal contamination in soils were determined and compared. Results of contaminated factor (CF) of Cu, Cr, Ni, and V were very high in the impacted soils whereas CF of Pb indicated considerable level of contamination. Pollution load index was greater than 1 which implies severe pollution in all the impacted soils while; the control soils indicated a pollution load index of less than 1 showing no pollution. Enrichment factor values of the impacted soils were between 0 and 1, which reveals background enrichment showing the presence of the metals above the threshold values. This may be attributed to anthropogenic sources especially oil spill contamination. The results of geo-accumulation index of Zn, Pb, and V showed considerable accumulation whereas, Fe, Cu, Cr and Ni indicated unpolluted to moderately pollution. Results of V, Ni, Pb, and Cr may be attributed to anthropogenic origin, which are in agreement with the calculated values of the enrichment factor. Results suggest the need for environmental risk assessment and/or remediation of the numerous oil spill sites for soil health and wellbeing of humans.