LEVELS, ECOLOGICAL AND HUMAN HEALTH RISK ASSESSMENT OF HEAVY METALS IN SOILS FROM SITES NEIGHBORING PETROL STATIONS IN KOGI STATE, NIGERIA

Abstract

Soil pollution caused by heavy metals has become the subject of many research. This is because heavy metals are highly toxic, ubiquitous and bio-accumulates. This study was carried out to investigate the levels of heavy metal pollution in soils around petrol stations within three major towns in Kogi State, Central Nigeria. Soil samples were collected at depths of 0 - 30 cm between the months of September and October, 2020 and subjected to elemental analysis using Atomic Absorption Spectroscopy (AAS). The total concentrations of the studied metals varied between 0.0102 - 0.0743 mg/kg Cd; 0.009 - 0.0439 mg/kg Cr; 0.0002 - 0.0099 mg/kg Pb; 4.99 - 28.1 mg/kg Cu and 168 – 677 mg/kg Fe. The mean concentrations of the detected metals - Cd, Cr, Pb, Cu and Fe in the study area varied thus: 0.0391, 0.0241, 0.00552, 16.9 and 388 mg/kg respectively. The decreasing trend of heavy metals in all the sample locations was in the order of: Fe > Cu > Cd > Cr > Pb. Ecological/human health risk assessment tools such as Contamination Factor (CF), Degree of Contamination (Cd), Geo-accumulation Index (Igeo), Pollution Load Index (PLI) and Enrichment factor (EF) were employed to ascertain soil health status in the area. Results reveals low level of soil pollution with Cd, Cr, Pb, Fe and moderate pollution with Cu, while metal enrichment factor shows extremely high enrichment of Cd and Cu. Correlation study reveals strong positive relationship among Cd/Cr (r = 0.835), Cd/Cu (r = 0.699) and Cu/Cr (r = 0.859) at 5 % level of significance, indicating that soil contamination by the metals originated from a common anthropogenic sources such as different activities within the petrol stations including fuel spills, combustion of fossil fuel, leakage of underground tanks and pipes, wear and tear of vehicle tyres, engine parts and brake shoes as well as emissions from agricultural areas in proximity to the petrol stations. Since some of these metals are toxic even at low concentrations, it is therefore, recommended that the Department of Petroleum Resources (DPR) and other regulatory agencies frequently monitor the levels of these pollutants within the area and also ensure strict adherence to guidelines by petrol stations owners during sitting and operations to ensure a healthy environment.