Toxicological assessment of heavy metals accumulated in vegetables and fruits grown in Ginfel river near Sheba Tannery, Tigray, Northern Ethiopia

摘要

The accumulation of heavy metals in vegetables resulting from irrigation with contaminated water obtained from industrial effluents may create a potential public health risk. We quantified the concentration of heavy metals (Cu, Zn, Fe, Mn, Cr, Cd, Ni, Co and Pb) in soil, vegetables and the water used for irrigation at two sites (Laelay Wukro and Tahtay Wukro) around Wukro Town, Tigray, Northern Ethiopia. The concentrations of heavy metals in irrigation water measured during this study were lower than permissible limits of heavy metals allowed for irrigation water. The mean concentrations of heavy metals in irrigated soil samples obtained from Tahtay Wukro were higher for Mn, Zn, Cr, and Cu. The overall results of soil samples ranged 2.62-827,1.4-51.6,25.5-33.6,23.5-28.2, 2.52-25.1,15-17.8,3-4,2.5-40.49 and 0.7-0.8 mg/kg for Mn, Zn, Cr, Ni, Cu, Co, Pb, Fe and Cd, respectively. Higher concentrations of heavy metals were also observed in vegetable samples from Tahtay Wukro. Pb was found to accumulate the most in all vegetable samples. It was observed that green pepper and lettuce accumulate high amounts of Cu and Zn; Swiss chard accumulates excessive amounts of Fe, Mn, Cr, Cd, Ni and Co; lettuce and tomato higher amounts of Cd; and green pepper, tomato and onion a higher concentration of Pb. Significant differences in the elemental concentrations between the vegetables analyzed from Laelay and Tahtay Wukro were observed. This was attributed in part to the geological nature of the study area and the discharges from the town and from a tannery. The results also indicate that Fe, Pb and Cd have high transfer factor values (mean values: 42.89, 0.84 and 0.37, respectively). The transfer pattern for heavy metals in different vegetables showed a trend in the order: Fe > Pb > Cd > Mn > Cu > Zn > -Ni>Zn>Cr=Co. The heavy metal contamination of vegetables grown in Tahtay Wukro, located downstream of the tannery, may pose increased health risks in the future to the local population through consumption of vegetables.