Heavy metals concentration in teak (<i>Tectona grandis</i> Linn. F.) and topsoil at roadside in University of Benin, Benin City, Nigeria

Abstract

This research was aimed at detecting some heavy metal ions in selected tissues of a standing twenty two years old Teak (Tectona grandis Linn. F.) trees and the topsoil around them at varied distance from a road within the campus of University of Benin, Benin City, Nigeria. Concentration levels of seven types of heavy metal ions were evaluated in the different samples using standard procedures. The results showed that Cu, Cr, Zn, Mn and Fe were detected in the samples while Cd and Pb were not detected. The concentration of Cu was highest (0.22±0.02μg/g) in leaves at a distance of 5.85m from the road while it was lowest in bark (0.09±0.01μg/g) and leaves (0.09±0.01μg/g) at a distance of 24.10m from the road. The concentration of Cr was found to be 0.40±0.03μg/g and 0.40±0.08μg/g in topsoil samples at distance of 5.85m and 18.60m from the road respectively but has a value of 0.17±0.002μg/g in leaves at a distance of 24.10m from the road. It was also observed that concentration of Zn was 0.93±0.06μg/g in leaves at a distance of 5.85m from the road but was 0.05±0.03μg/g in topsoil at a distance of 24.10m from the road. Additionally, the concentration of Mn was highest in topsoil (1.10±0.006μg/g) at a distance of 18.60m from the road but was lowest in bark (0.20±0.02μg/g) at a distance of 24.10m from the road. The concentration of Fe ions was found to be highest in topsoil samples (89.12±0.55μg/g) at a distance of 5.85m from the road but was lowest in bark (2.07±0.07μg/g) at a distance of 24.10m from the road. The results revealed a somewhat common trend where concentrations of all the detected heavy metal ions declined in the samples of topsoil and teak’s tissues as the distance of the locations where the samples were sourced increased from the roadside. The outcomes of this research appeared to have implicated automobiles as the main source of these pollutants; nevertheless, more intensive scientific investigations are necessary to provide answers to existing questions concerning ascertaining the source(s) of these pollutants, if not from petroleum fuelled automobiles, and the possible roles and ability of this tree species, or otherwise, in contributing to environmental cleaning in the study area.

Keywords: Toxic/noxious substances, Soil pollution, Heavy metal contamination, Phytoremediation