Assessment of single extraction methods for the prediction of bioavailability of metals to Vigna unguiculata l (beans) grown on crude oil contaminated soil

Abstract

The bioavailability of toxic metals in the soils is increasingly an important issue as soil always becomes contaminated from various anthropogenic activities. Total concentrations of metals in the soils are generally poor indicators of metal toxicity because they exit in different solution and solid phase forms that can differ in terms of their bioavailability. As such, regulators are looking at bioavailability as an indicator of risk associated with metal contamination in soils. Since the bioavailability of metals, their biological uptake and eco-toxicological effect on soil biota can be understood better in terms of their biogeochemical forms, the study assessed the effect of crude oil applied at rates, 0, 2, 5, and 10% on the fractional chemical forms and availability of some metals in soils from Usen, Edo State, with no known crude oil contamination and soil from a crude oil spill site in Ubeji, Delta State, Nigeria, using several techniques as a basis for predicting metal uptake by plants. Bean seeds were grown in the contaminated soil for 21days and the metal concentrations in the seedlings were compared with the total soil metal concentrations, bioavailable metal concentrations and EDTA-extractable metal concentrations. Keywords : bioavailability, chemical forms, crude oil-contaminated soil, EDTA, metal concentrations,