Assessment of Heavy Metals Bioaccumulation in Vegetables Grown in Three Local Government Areas of Kaduna State, Nigeria

Abstract

Vegetables are among the major sources of proteins and vitamins in human diets. However, they have high potential for contamination by heavy metals which pose serious public health threats. A study was conducted to assess the levels of heavy metals bioaccumulation in two leafy vegetables: Spinach (Spinacia oleracea) and Cabbage (Brassica oleracea).grown in three local government areas (Giwa, Sabon-gari and Hunkuyi) of Kaduna State. The four heavy metals assessed were: Lead (Pb), Copper (Cu), Cobalt (Co) and Zinc (Zn) in the two leafy vegetables: Atomic Absorption Spectrophotometer (AAS) was used to detect and analyze heavy metals bioaccumulation in the vegetables and soil samples. The sampling locations were selected on the basis of anticipated magnitude of the extent of contamination of the water used for irrigating these vegetables in such areas. The experiment was arranged in completely randomized design with three replications. Data obtained was analyzed using Analysis of Variance with Duncan’s New Multiple Range Test used to separate significant means at 5% level. The result obtained revealed significant difference (P≤0.05) in the heavy metals bioaccumulation in the vegetables and the soils on which they were grown. The result showed that the concentration for Co and Cu were lower than the maximum permissible limits standards as such were non-lethal. However, the accumulation of Pb and Zn in the vegetables was above tolerable limits. This inferred that, vegetables from Sabon-gari, Giwa and Hunkuyi grown along road sides and irrigated with water containing agricultural residues accumulated higher concentration of Pb and Zn. This can be attributed to the intense use of agro-chemicals such as fertilizer and pesticides as well as domestic and industrial discharges in the area. This also suggests a high probability of lethal toxicity due to Pb and Zn in these vegetables. It is therefore recommended that, people should abstain from consuming these heavy metals contaminated vegetables due to significant health implications they posed on to the public health. More so, consumption of vegetables irrigated with waste water or close to road side should be avoided.