Transfer Characteristics of Trace Metals from Soil to the Edible Parts of Some Vegetable Species Grown in Ibeno, South-South Nigeria

Abstract

The aim of this study was to assess the levels of trace metal in soils and leafy vegetables at Ibeno, as a result of crude oil exploration activities in the area. The study areas were Mkpanak, Iwuoachang and Ukpenekang all in Ibeno Local Government Area of Akwa Ibom State, Nigeria. Soil and vegetable samples (Telfaria occidentalis, Spinacia oleracea and Talinum triangulare) were collected randomly from sampling sites and analyzed for trace metals (Pb, Zn, Cu, Co and Cd) using atomic absorption spectrophotometric technique. Bioaccumulation of trace metals in plant parts were estimated as transfer factors (TF). Metal concentrations in the soil ranged from          85.56 mg/kg to 143.84 mg/kg for Zn, 39.24 mg/kg to 52.55 mg/kg for Co, 2.66 mg/kg to 4.50 mg/kg for Cu and 0.01 mg/kg for Pb and Cd in the soil. Trace metal levels in soils were below Federal Environmental Protection Agency (FEPA), Nigeria limits for agricultural soils except for Co. Higher levels (P< 0.05) of metals were measured in soils at the various locations compared to the control soils. At Levels of trace metals in vegetables varied in the order, Telfaria occidentalis>           Spinacia oleracea>Talinum triangulare and the concentrations were higher than WHO/FAO limits. TF values showed higher accumulation of Pb with a Pb>Cd>Cu>Zn>Co gradient. The results showed that Telfaria occidentalis exhibited the most ability to accumulate trace metals followed by Spinacia oleracea and Talinum triangulare. This showed the potential of using Telfaria occidentalis as an indicator of trace metal pollution in soils. The high TFs observed in this study indicated bioaccumulation of the metals in plants and a possibility of systemic toxicity when these plants are consumed by either humans or animals.