Assessment of Heavy Metals in Designated Tropical Soils and Vegetables Using X-Ray Fluorescence Spectroscopy

Abstract

X-ray fluorescence (XRF) technique was used to investigate the accumulation of heavy metals in fluted pumpkin (Telfairia occidentalis), African spinach (Amaranthus hybridus) and water leaf (Talinum triangulare) harvested from two (2) farms in St. Louis and Osuma Layout in Owo Local Government Area, Ondo State. The heavy metals detected, chromium (Cr), zinc (Zn), manganese (Mn), iron (Fe), titanium (Ti), strontium (Sr) and aluminium (Al) were more available in the soil samples than the vegetable samples except Zn and Mn. Although their proportions were higher than the permissible limits of WHO/FAO for soils and plants, their bioaccumulation in the soil samples was Al > Fe > Ti > Mn > Sr > Cr > Zn and bioavailability in the vegetable samples was Al > Fe > Ti > Mn > Sr > Zn > Cr. The peak concentrations (%) of Cr (0.015±0.001) and Mn (0.39±0.03) were obtained in Talinum triangulare from Osuma Layout (TtOL), Zn (0.072±0.003) and Fe (3.00±0.01) in Talinum triangulare from St. Louis (TtSL), Ti (1.31±0.01) and Sr (0.068±0.001) in Telfairia occidentalis from Osuma Layout (ToOL) while Al (6.33±0.03) in Amaranthum hybridus from St. Louis (AhSL). Both negative and positive correlations existed between metal pairs (p < 0.05). Based on their bio-concentration factor (BCF) values, TtOL was Cr hyperaccumulator and ToOL was both Mn and Ti hyperaccumulators. Zn hyperaccumulation was competitive and was in the decreasing order of TtOL > TtSL > ToSL (Telfairia occidentalis from St. Louis) > AhSL. Among all the vegetable samples, TtSL was the most significant nonaccumulator for Cr. All the vegetable samples studied have potential for selective phytoextraction of heavy metals from polluted soils.

Keywords: Heavy metals, hyperaccumulator, phytoextraction, bio-concentration factor (BCF)

DOI: 10.7176/JNSR/14-8-01

Publication date:May 31^st 2023