Assessment of some heavy metals concentration in soil and irrigated vegetable (Hibiscus sabdariffa) in Mubi Metropolis

This research work aimed at assessment of some heavy metal concentration (Fe, Mn, Cu, Ni, Pb, Zn) in soil and their uptake by Hibiscus sabdariffa vegetable in irrigation areas, and to ascertain the danger posed from the consumption of these vegetable to human health. Samples were collected from four different locations and analyzed using bulk scientific Atomic Absorption Spectrophotometer (AAS). The concentration of heavy metals (mg/kg) in agricultural soil collected from different sites along river Yadzaram ranged from 8.33 to 15.54 for Fe, 0.051 to 0.227 for Cu, 7.245 to 8.545 for Mn, 0.001 to 0.002 for Ni, 0.474 to 1.744 for Zn, and 0.001 to 0.005 for Pb. Fe concentration in plants (Hibiscus sabdariffa) ranged between 6.50 to 16.42 mg/kg in all four sites of the studied area, Cu values ranged between 0.30 to 0.72 mg/kg. The concentration of Mn in plants ranged from 2.73 to 12.09 mg/kg, Ni concentration in plant samples from four site varied from 0.001 to 0.004 mg/kg, Zn concentration varied from 0.98 to 1.99 mg/kg and Pb range values of 0.00 to 0.007 mg/kg. The contamination/ pollution index of heavy metals calculated for soil revealed that all sites were polluted with Fe at Kwacham, Wuro-gude, Kwachiffa and Sabon Gari site which suggested that it might pose negative effect on plants and soil environments while Ni, Zn, Mn, Cu and Pb are below range and will have no negative effect on soil, plant and environments.

Vegetables are rich sources of vitamin, minerals, and fibers, and also have beneficial anti oxidative effects. However, intake of heavy metal contaminated vegetables may pose a risk to the human health. This is because, heavy metals have the ability to accumulate in living organisms and at elevated levels they can be toxic. It has been reported that prolong consumption of unsafe concentration of heavy metals through foodstuffs may lead to the chronic accumulation of the metals in the kidney and liver of humans causing disruption of numerous biochemical processes, leading to cardiovascular, nervous, kidney and borne diseases (Trichopoulos, 1997, Jarup, 2003). Hibiscus sabdariffa belongs to the family of Malvaceae and common names are Roselle and Sorrel.

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