Analysis of potentially toxic elements from selected mechanical workshops using the geo-accumulation index and principal component analysis in Omu-Aran Community, Nigeria

Abstract

Bioaccumulation of potentially toxic elements in soil threatens public health and the ecosystem. This study aims to assess the concentration of potentially toxic elements (chromium (Cr), lead (Pb), iron (Fe), arsenic (As), and cadmium (Cd)) in selected automobile workshop premises in Omu-Aran, Nigeria. Forty-eight samples were collected at a depth (15 cm) in six locations, including a control point. Acid digestion was carried out to prepare the soil samples before assessing their concentration via an atomic absorption spectrophotometer. Geoaccumulation index (Igeo) was used to classify the level of contamination. Statistical analysis, which includes principal component analysis (PCA) and Pearson's correlation, was also determined. The difference in concentration was determined using ANOVA. In the study area, the lowest observed concentration values for Cr, Pb, Fe, As, and Cd, which are 0.246 ± 0.002 mg/kg, 0.178 ± 0.001 mg/ kg, 90.715 ± 0.038 mg/kg, 0.012 ± 0.004 mg/kg, and 0.078 ± 0.004 mg/kg, respectively, are relatively higher than observed for the control. The observed potentially toxic elements fall within three Igeo based on Muller's interpretation; heavily to extremely contaminated (Cd), moderately to heavily contaminated (Pb, Cr, and As), and uncontaminated to moderately contaminated (Fe). PCA shows that two principal components (PC) account for up to 91.052% of the original mean dataset variability. PC1 explains 67.723% of the total variance associated with Cd, Cr, Fe, Pb, and As, indicating anthropogenic is the primary source of these potentially toxic elements. The PC2 accounted for 23.329%, with Pb and As significant contributors. Cadmium contamination of soil was the most influential, with an Igeo value ranging from 4 to 5. Residents in the polluted region face considerable health risks from potentially toxic elements.