Elemental Compositions of Tropical Vegetables and Soils in Edo State, Nigeria Using X-ray Fluorescence Technique

Aim: This research work investigated the bioaccumulation of metals in selected edible vegetables from the soils on which they were grown.

Place of Study: Two (2) different study locations were chosen from Etsako-West Local Government Areas of Edo State of the Federal Republic of Nigeria. Etsako-West Local Government Area has an area of 660 km² on Latitude 7.0878ºN and Longitude 6.5010ºE with the headquarters in Auchi.

Methodology: Leaves of fluted pumpkin (Telfairia occidentalis), African spinach (Amaranthus hybridus) and water leaf (Talinum triangulare) and soil samples were randomly collected from Water Board and Iyerekhu farms in Etsako-West Local Government Area, Edo State, Nigeria and were analysed for their elemental compositions, using X-ray fluorescence (XRF) technique.

Results: In both soil and plant samples, silicon (Si) were most abundant, ranging between 18.85 and 38.91%. The decreasing order of abundance of elements in the plant samples was Si>K>Ca>Al>Cl>S>P>Mg>Fe>Ti>Mn>Zn>Sr>Cr. Toxic heavy metals such as As, Pb, Co, Cd and Cu were not detected in both soil and vegetable samples. The concentrations of the elements in the samples were higher than the permissible limits of WHO/FAO and EU for soils and plants, except Zn in the soil samples and Talinum triangulare from Iyerekhu farm. The peak transfer factor, 238.43 was obtained for K in Talinum triangulare from Iyerekhu farm while the least is 0.00 for Zn in all the plant samples. The overall mean ability of plant to absorb elements from the soil was most with Talinum triangulare, followed by Amaranthus hybridus.

Conclusion: The vegetables studied had high tendency to bioaccumulate the bioavailable metals in soils. However, all the vegetables studied, especially T. triangulare could be used in phytoremediation of polluted soils.