PROFILING OF HEAVY METALS IN SOIL AND VEGETABLE SAMPLES OF OSUN FREE TRADE ZONE (PHASE 1) NIGERIA

Abstract

Assessment of heavy metal contents in soil and vegetable (Talinium triangulare) samples from fifteen different points on the 30 hectares first phase of the Osun state free trade zone, located between Osogbo (7.75412ºN; 4.56396ºE) and Ede (7.70330ºN; 4.44612ºE), was undertaken to establish the quality and quantity of these metals, using EDXRF, before any industrial activity will commence and, as such, infer the contamination status of the soil and vegetable growing naturally thereon. Top (0-15cm) and sub (15-30cm) soil were analyzed for each geo-referenced spot chosen. Zinc showed the highest concentration, ranging between 5 ± 0 and 2557± 100 mg/kg while Tungsten was the least, 25 ± 1 mg/kg, was found only in sample 4A. Other metals detected in measurable quantities were; Pb, Fe, Mn, Ti, Ni, Cu, Sr, Zr, Bi, As, K and Ca. The vegetables had; Zn, Se, Ba, V, Sr, Co, Mn, Cr, Ca and K. Among the toxic heavy metals Se (168±38-279±49) is highest and V (7±3-9±3) is least. Six metals common to the soil and vegetable: K, Ca, Fe, Mn, Sr and Zn, showed positive correlations. Ni, Cu, Pb and Zn in the soil and Cr, Co, Se and V in vegetable gave values above critical concentrations.