Quantitative Determination of Heavy Metal Concentrations in Onion Leaves

The concentration (mg/kg dry weight) of Cd, Cr and Pb were determined in onion leaves samples using the atomic absorption spectrometry. A total of 16 onion leaves each were collected from both the study and control sites for analysis. The heavy metals, Cd, Cr and Pb in onion leaves of study sites were found in the range of 0.667 – 0.933, 3.870 – 7.870 and 5.870 – 7.537mg/kg respectively, while the results of control sites showed values ranging from 0.583 – 0.700, 0.447 – 0.842 and 3.833 – 7.333mg/kg for Cd, Cr and Pb respectively. The trend of abundance of heavy metals in both sites followed the same sequence: Pb > Cr > Cd. The metals levels in both sites are higher than WHO/EU recommended limits with exception of Cd. The high levels of the metals suggest that effluent water irrigated fields could be indicative of bio-accumulation of the metals in the leaves, consequently putting the consumers of this vegetable crop are at health risk.