Bioaccumulation of Lead and Cadmium from Contaminated Soil into Amaranthus Hybridus in Grown Irrigation Farm Lands in Zaria, Kaduna State, Nigeria

ABSTRACT
The study on bioaccumulation of lead and cadmium from contaminated soil into Amaranthus hybridus grown in irrigation farm lands in zaria, Kaduna state, Nigeria was carried out to assess the risk to human health by heavy metals (Pb and Cd) through the intake of grown vegetables (Amaranthus hybridus) from bomo lake, river galma and borehole water irrigated site. The samples collected (A. hybridus and soil) were separately digested and the heavy metals were analyzed using Atomic absorption spectrophotometer (A. A. S.). The results obtained from this study showed that lead concentrations (1.65 – 6.05 mg/kg in soil, 1.21 – 3.25mg/kg in roots, 0.99 – 2.95mg/kg in
stems and 0.72 – 1.96 in leaves) were found to be higher than cadmium (0.05 – 0.11mg/kg in soil, 0.02 – 0.09mg/kg in roots, 0.01 – 0.08mg/kg in stems and 0.01 – 0.07mg/kg in leaves) in all the samples collected (Amaranthus hybridus and soil). This showed that high concentration of lead in all the samples may pose health risk to the vegetable, farmers and consumers. Heavy metal concentrations (lead and cadmium) were several folds higher in all the collected samples from bomo lake and river galma irrigated sites (Pb in soil: 3.69 – 6.05mg/kg and Cd in soil: 0.09 – 0.11mg/kg. Pb in leaves, stems and roots: 2.10 – 3.25mg/kg, 1.10 – 2.95mg/kg and 1.17- 1.96mg/kg respectively and Cd in leaves, stems and roots: 0.02 – 0.09mg/kg, 0.02 – 0.08mg/kg and 0.01 – 0.07mg/kg respectively) compared to borehole water irrigated sites (Pb in soil: 1.65 –2.06mg/kg and Cd in soil: 0.05mg/kg. Pb in leaves, stems and roots: 1.21 – 2.10mg/kg, 0.99 –1.70mg/kg and 0.72- 1.40mg/kg respectively and Cd in leaves, stems and roots: 0.03 – 0.08mg/kg, 0.01 – 0.05mg/kg and 0.01 – 0.04mg/kg respectively). Pb concentrations (0.72 – 6.05mg/kg) were above the permissible limit as recommended by the FAO/WHO (2001) standards in all the samples (Amaranthus hybridus and soil) but Cd concentrations was found to be below the permissible limits
(0.01 – 0.11mg/kg). The higher values of metal pollution index (0.02 – 0.07mg/kg in bomo and 0.01 – 0.06mg/kg in galma) and health risk index (0.13 – 0.08 in bomo and galma treated with lake and river water, 0.07 – 0.80mg/kg in bomo and galma treated with borehole water) indicated heavy metal contamination in the bomo lake and river galma irrigated site that presented a significant threat of negative impact on human health. The study suggests that bomo lake and river galma irrigation used in the study may lead to accumulation of heavy metals in the vegetable causing potential health risks to consumers.