Heavy Metal Contents in Soil and Leaf with Relative BioaccumulationFactor of Selected Locations at Awka, Nigeria

Abstract

Heavy metals are bioaccumulated and biotransferred by both natural and anthropogenic means. Heavy metal contamination in Soils and plants is one of the main issues in the entire globe which needed urgent attention because heavy metals above their normal limits are extremely hazardous to both plant and animals. Thus, this study was designed to evaluate the level of concentration of heavy metals in agricultural soils and vegetable (Telfairia occidentalis) grown on the soils in five different villages (Okpuno, Amawbia, Isu aniocha, Ifite-Awka and Amansea) within Awka capital territory, Anambra state, Nigeria. The samples of both the leaf and soil samples were collected from 5 different locations and were prepared, digested and the heavy metal concentration were determined using Atomic Absorption Spectroscopy (AAS 500 Model). The result obtained showed that the mean concentration of the toxic metals in the soil were in the decreasing order: Cr>As>Fe>Se>Ni>Hg>Pb>Cd, while the mean metal concentration in vegetable samples were in this decreasing order:
Cr>Fe>Se>Ni>Cd>Pb>As>Hg. Chromium metal had the highest concentration in all the studied agricultural soils. Moreover, Cr metal also had the highest concentration in the vegetable samples in all locations except for that of Okpuno. The leaf samples had significant difference in the transfer factors of metals relative to the availability of same metals in the soil. The TF ranged from 0.000 to 9.98. The peak TF (9.98) of Se metal were observed in Amansea followed by 8.86 of Iron (Fe) obtained in Amawbia and the least (0.000) of Lead (Pb) were observed in Isu-Aniocha and also that of Nickel that were observed both in Ifite-Awka and Amansea. The study observed that the concentration of heavy metals in the sampled agricultural soils from different locations and the vegetable samples were lower than the WHO permissible limits except the mean concentration of Cd that were above the limit in vegetable samples and all the agricultural soils from the 5 different locations. This also suggests that at present, the health effect from the consumption of Telfairia accidentalis is very minimal in the sampled locations because of the low concentration of heavy metals in most of the sampled agricultural soils and vegetables. However, continuous exposure to these heavy metals to local residents in the sampled areas may cause serious health implications.