Assessment of heavy metals bioaccumulation in rice (Oryza sativa L.) seeds grown along Zaria-Kankara road, Northwestern Nigeria

Abstract

Heavy metal contamination of farmlands is one of the major threats to food security in Nigeria. Cereal crops have the ability to absorb these heavy metals which when consumed by human and animals manifest several clinical symptoms. This research was carried out to determine the level of heavy metals concentration in the soil and seeds of rice (Oryza sativa) grown along Zaria-Kankara road. Soil and rice seeds samples were collected at a distance of 5, 10, 20m, 40and 60 m away from the road sides. The samples were analyzed for Zinc (Zn), Lead (Pb), Manganese (Mn) and Cadmium (Cd) concentrations in a Completely Randomized Design with three replications. The data obtained were analyzed using Analysis of variance with Duncan’s Multiple Range Test used to separate significant means at 5% levels. The result obtained revealed significant difference (P≤0.05) in the levels of Zn, Pb and Mn in the soils and seeds of rice which decrease with increase in distance from the road side. High heavy metals concentrations in the soil and seeds of rice above exceed limits indicated the relative abundance of such elements in relation to vehicular density and anthropogenic activities such as fertilizer and pesticides application. The values of the heavy metals accumulated in the rice seeds showed that consumption of rice seeds grown close to the road sides is hazardous and posed threat to public health. Therefore, it was recommended that, rice should be grown at a distance of not less than 40-60 m from the road sides.