Evaluation of Selected Heavy Metal Concentration of Soil Along Some Highways in Imo State, Nigeria
Received: 30 June 2025 | Revised: 18 August 2025 | Accepted: 22 August 2025 | Published Online: 10 September 2025
Abstract
This study evaluated the concentration of selected heavy metals (Pb, As, Zn, Cu, Hg) in soils along two major highways, Owerri–Aba and Owerri–Okigwe, and a non-highway control site at Egbeada in Imo State, Nigeria. Soil samples were collected at depths of 0–15 cm and 15–30 cm, and at distances of 0–50 m and 50–100 m from the road. Laboratory analyses were conducted at the Soil Science Department Laboratory of the Federal College of Land Resources Technology, Owerri, to determine both physical (particle size distribution, bulk density, porosity, moisture content) and chemical (pH, organic carbon, total nitrogen, available phosphorus, exchangeable bases, cation exchange capacity) properties, alongside heavy metal concentrations using Atomic Absorption Spectrophotometry. Results indicated higher concentrations of heavy metals along highways compared to the control site, with Zn showing the highest levels and Hg the lowest. Concentrations decreased with increasing distance from the road and with soil depth. Positive correlations were observed between heavy metal content and parameters such as moisture content, bulk density, and cation exchange capacity, while negative correlations were found with organic carbon, available phosphorus, total nitrogen, sand, and clay content. The concentrations of certain metals along highways exceeded WHO permissible limits, indicating potential environmental and public health risks.