Heavy metals bioconcentration from soil to vegetables and appraisal of health risk in Koka and Wonji farms, Ethiopia

Heavy metal accumulation in agricultural crops has grown a major concern globally as a result of a significant health impact on human. The quantification of heavy metals (Cd, Pb, Cr, Zn, Cu, and Ni) in the soil and vegetables at two sites (Koka and Wonji Gefersa) was done using flame atomic absorption spectrophotometer. The mean concentrations of heavy metals in vegetable fields' soil samples obtained from Koka were higher for Pb, Cr, Zn, Cu, and Ni. The overall results of soil samples ranged 0.52-0.93, 13.6-27.3, 10.0-21.8, 44.4-88.5, 11.9-30.3, and 14.7-34.5 mg kg(-1) for Cd, Pb, Cr, Zn, Cu, and Ni, respectively. The concentrations of heavy metals were maximum for Cd (0.41 +/- 0.03 mg kg(-1)), Pb (0.54 +/- 0.11 mg kg(-1)), Zn (14.4 +/- 0.72 mg kg(-1)), Cu (2.84 +/- 0.27 mg kg(-1)), and Ni (1.09 +/- 0.11 mg kg(-1)) in Cabbage and for Cr (2.63 +/- 0.11 mg kg(-1)) in green pepper. The result indicated that Cd has high transfer factor value and Pb was the lowest. The transfer pattern for heavy metals in different vegetables showed a trend in the order: Cd > Zn > Cu > Cr > Ni > Pb. Among different vegetables, cabbage showed the highest value of metal pollution index and bean had the lowest value. Hazard index of all the vegetables was less than unity; thus, the consumption of these vegetables is unlikely to pose health risks to the target population.