Comparative Phytoaccumulation of Lead Uptake by Oryza sativa and Zea mays L

Abstract

The identification of chemical forms of lead (Pb) in agricultural samples is of interest for the evaluation of its mobility, bioavailability and ecotoxicity. Heavy metals are among the most important sorts of contaminant in the environment and metal pollution is a global concern and also health hazardous to human health. This research was carried out to determine and compare the level of heavy metal uptake (Pb) in both Oryza sativa and Zea mays planted on contaminated soil. A 6 kg of soil was contaminated with 20 g of Pb (NO₃)₂ which contains 12.51 g of Pb. Oryza sativa and Zea mays was planted on this contaminated soil. Germination begins after 5 days of plantation for both Oryza sativa and Zea mays. Plant growths continuous in three different containers each for 30 days. A similar trend was carried out for the uncontaminated soil which also germinates after 6 days of plantation.  It was observed that contaminated one’s germination was faster than uncontaminated (Control) and it has effect on the germination process of both Oryza sativa and Zea mays. The level of heavy metals in the soil and plant was determined using Atomic Absorption Spectrophotometer (AAS) analysis. Analysis of the plant and soil samples reveals that the concentration of Pb in Oryza sativa were, 0.425, 0.514 and 0.498, mg/dm³, for plant and in soil were 0.855, 0.715, and 0.725 mg/dm³ respectively. While for Zea mays were 0.329, 0.293 and 0.272 mg/dm³ for plant and for the soil was 0.953, 0.982 and 0.978 mg/dm³ respectively. It shows that the uptake of the metal is high. All the values obtained from the Soil analysis for Zea mays and Oryza sativa were below the permissible limit recommended by WHO. But in both plant Oryza sativa and Zea mays, it has exceeded the maximum permissible limit recommended by WHO/FAO which shows that the absorption is high. Therefore, the consumption of these plants, planted on contaminated soil as food may pose health hazards to humans and animals. The mean, standard deviation and transfer factor of both the plant and soil samples was all calculated. The result also shows that both Oryza sativa and Zea mays has the ability to phytoremediate to a very small extend. Farmers are advised to dig wells for irrigation as their source of water. The general public should be enlightened to avoid discarding solid waste dumps, garbage and animal excretions on agricultural lands because they are also sources of heavy metals. Further research should be carried out in the future in order to explore more plants that have higher ability to phytoremediation.