Assessment of heavy metal pollution in soils: a case study of Nsukka metropolis

Abstract

Owing to population growth and urbanization, there has been an increase in the number of auto mechanic workshops, vulcanizer’s shops and engine oil retail shops along the roads within Nsukka with a direct increase in heavy metal concentration in dust. Emissions from these activities pose serious environmental concern along the major roads. This study is centered on the assessment of heavy metal pollution in dust and top soil along major roads within Nsukka metropolis. Soil and dust samples were collected along major roads at maximum distance of five meters from the roads edge, with control samples collected 400 m away from the nearest road. Heavy metals (Cadmium, Zinc, Iron, Lead, Chromium, Arsenic, Copper, Nickel, and Manganese) concentrations in the dust and soil were analyzed using Atomic Absorption Spectrophotometry method. The result of the analyzed heavy metal concentration showed no significant variation from the background concentration. The concentrations of Pb and Cr showed little variation, whereas As showed the greatest variation from the background value. The results of heavy metals contamination factor in soil and dust ranged from low contamination to very high contamination (CF < 1; to CF ≥ 6). High and very high contamination values were obtained for As, Cr, and Mn in both dust and soil samples. The enrichment factor of heavy metals ranged from EF ≤ 1 (background rank) to EF> 40 (extremely high enrichment). Among the analyzed heavy metals, Zn, Pb, As, and Cr showed the highest enrichments in both soil and dust samples respectively. The result of Igeo ranged from Igeo ≤ 0 (uncontaminated) to 2 < Igeo < 3 (moderately to heavily contaminated). In the dust and soil samples, Igeo for Zn, Pb, Cd, Ni, and Cu show no contamination; Igeo for As and Cr showed moderate contaminations in some locations whereas that of Mn showed moderate to heavy contamination. Results of PLI ranged from PLI < 1 (no pollution) to 3 <PLI (extremely heavy pollution).