Geochemical and Multi-Index Ecological Risk Assessment of Heavy Metal Contamination in Surface Soils of Auto-Mechanic Workshops in Effurun, Niger Delta, Nigeria

Abstract

This study investigates the pollution levels and ecological risks posed by heavy metals
in surface soils of auto-mechanic workshops in Effurun, Niger Delta, Nigeria. A total
of forty soil samples, composited into eight representative samples (including a
control), were systematically collected from various parts of the auto-mechanic
village, and analyzed using Atomic Absorption Spectrophotometry. Mean
concentrations (mg/kg) of heavy metals across sampled sites followed the order: Fe
(806.85) >Zn (128.46)>Cu (33.68) >Pb (21.49) >Ni (5.55) >Cr (1.10)>Cd (0.29),
significantly exceeding control values and international guidelines. Contamination
assessment using multiple indices revealed: extreme contamination factors for Pb
(CF=860.27), Cr (CF=2076), and Ni (CF=2776.5) at site C6; geo-accumulation indices
indicating extreme pollution (Igeo>5) for multiple metals; and enrichment factors
showing moderate to severe anthropogenic inputs (EF=3.8-22.5). All sites exhibited
Pollution Load Index values exceeding 1 (ranging from 1.32-57.65), indicating soil
quality deterioration. Site C6 emerged as a critical pollution hotspot with extremely
high ecological risk (RI=24,116.15). Statistical analyses identified significant positive
correlations between Cu-Zn (r=0.809), Pb-Ni (r=0.841), and Cu-Ni (r=0.792).
Principal Component Analysis extracted three components explaining 76.1% of total
variance, while Hierarchical Cluster Analysis classified sites into three distinct
contamination levels. These findings demonstrate significant environmental
degradation and necessitate urgent environmental regulation, remediation efforts,
improved waste management, and continuous monitoring to mitigate ecological and
health risks in this sensitive region.