The Concentrations of Potentially Toxic Elements and Total Hydrocarbon in Soils of Niger Delta Region (Nigeria)

Abstract

The present study was aimed to determine the natural background level, threshold values and evaluate the pollution status of some heavy metals and total hydrocarbon contents in soils of the Niger Delta region, NDR, (Nigeria). In order to achieve this, thirty two composite soil samples were collected and investigated for pH, EC, OC, grain size, THC, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn. Analytical results show that the average concentration of total hydrocarbon contents (THC) exceeded the limit in soils for crude oil processing areas in Nigeria. The concentrations of Cd and Co in all the soils samples were higher than reported values for world soils. The average concentrations of Fe and Pb were higher than the background values. However, the concentrations of Cr, Cu, Fe, Mn, Ni, Pb, V and Zn in the soils were less than the average value for world soils. This suggests that these elements were naturally present at low concentrations. Contamination risk assessment based on the index of geoaccumulation (I-geo) values for all the samples corresponded to practically uncontaminated with the exception of THC (uncontaminated to moderately contaminated) and Cd (moderately contaminated). In addition, the pollution index (PI) values of the soil samples were low (PI < 1) indicating that on the overall the soils were not polluted. However, high values (PI > 1) in some locations reflected high concentrations of Cd, Cu and THC. The results suggests that the main source of elements in soils of the Niger delta is parent material, whereas increase in industrialization, especially, due to oil and gas related activities poses a significant impact on the distribution of some of these elements.

Keywords Heavy metals, Contamination, Soil, Niger Delta, Nigeria