Assessment of heavy metals contamination of soil and groundwater around selected petrol stations in Abeokuta Metropolis, Nigeria

Abstract

This study investigated heavy metals contamination of soil and groundwater in selected petrol stations with the following
codes: CNP, JKO, CDA, EP, NMS, MRS, FAG, LJO, DRL, and MNP in Abeokuta Metropolis. The metals were analysed in
twenty composite soil samples collected at depth 0-15 cm and 15-30 cm using soil auger. Groundwater samples were
collected into 2 litre pre-cleaned sample bottles from six hand-dug wells and four boreholes respectively. Heavy metals in
all samples were analysed using atomic absorption spectrophotometer. Concentrations of heavy metals in the soil were
in the order of Pb>Cr>Ni>Cu>Cd. Mean Pb concentrations in soils around the petrol stations ranged from 13.75 ? 0.50 in
CDA and 209.25?0.66 mgL-1 in LJO Petrol Station. Index of geo-accumulation (Igeo) indicated that LJO Petrol Station was
the most polluted by Pb with Igeo of 10.5 in the topsoil. The soils around the petrol stations had potential ecological risk
index (RI), which were above 200 showing high toxicity. The average concentrations of Pb were 0.19?0.03, 1.31?0.01,
3.52?0.61 mgL-1 for water from hand dug wells at JKO, NMS and MRS respectively, which were higher than the WHO
permissible limit. Sources of contamination of soil and groundwater around the petrol stations were spillage from dispensing
of petrol and leakages or seepages from the underground petrol tankers. Pollution from the petrol stations in Abeokuta
Metropolis contributes to heavy metal concentrations in the soil and groundwater, which is a potential threat to human
health