Comparison of phyto-accumulation of metals by <i>Vigna unguiculata</i> L. (bean) and <i>Zea mays</i> L. (maize) grown in crude oil contaminated soil

Abstract

The study compared the phyto-accumulation of copper (Cu), iron (Fe), lead (Pb), cadmium (Cd) and zinc (Zn) by bean and maize seedlings grown in crude oil-contaminated soils. A total of 300 bags containing 500g of soil were used for this study. Three viable seeds of bean and maize were planted in a set of 60 bags of sandy loam soil with no history of crude oil contamination, which served as control, 180 bags of sandy loam soil were mixed with crude oil to give 2%, 5% and 10% contamination, while another set of 60 bags had 500g of soil from crude oil spill site in Ubeji community, Niger Delta. Both plants were harvested 7, 14 and 21 days post germination and the soils and seedlings analyzed for some metals before and after planting. Metal levels in the crude oil contaminated soils were not detected for Cd but showed high concentrations for the other metals when compared with control. The values of Cu, Pb, Zn and Fe decreased in the crude oil contaminated soil and increased in both seedlings as the number of days increased. The study indicates that bean seedlings accumulated more Fe and Cu than maize whereas maize seedlings accumulated more Zn and Pb than bean in the crude oil contaminated soil. The results suggest that the plant species for phyto-accumulation measures for decontamination of crude oil contaminated soils is an important factor.

Keywords: bean, copper, iron, lead, maize, phyto-accumulation, sandy loam soil, zinc.