An assessment of toxic heavy metals in soil and plants (Allium cepa and Daucus carota) by GFAAS

Abstract

ABSTRACT Toxic metals were identified from soil and different edible and non edible parts of Allium cepa and Daucus Carota. Results showed that there is significant metal movement from soil to vegetables. Different vegetables have different mechanism of metal sorption and uptake. Levels of heavy metals in soil were in the order of Zn>Cu>Ni>Sb>Co>Mn>As>Cd>Pb>Cr before the cultivation of vegetables i.e. Allium cepa and Daucus carota. Ten in number heavy metals including essential metals i.e. Zinc, Copper and Manganese and non essential metals nickel cobalt, arsenic, cadmium, antimony, chromium and lead were selected for investigation. Samples were classified into soil before cultivation, after cultivation, edible and non edible parts of vegetables Allium cepa and Daucus carota. The results showed significant metal movement in the entire chain from soil to the different parts of vegetables. These vegetables were grown in the selected soil samples and heavy metals were estimated by using graphite furnace atomic absorption spectrometer. Soil samples were also analysed again and significant reduction in metal concentration was found after vegetation. Results of heavy metals in different parts of the Allium cepa and Daucus Carota showed a very interesting correlation that toxic metal movement was automatically stopped when reached near the edible part of the vegetables. It seems as if some natural barriers across the plant persist which prohibit the toxic metal movement towards the edible parts. It is quite evident from the results that metal movement from soil to vegetables is significant and it should remain same in the edible parts as well. But in edible parts metal amount was extraordinary low which can not be considered as dangerous for human health. The results provide useful biological and toxicological effect of toxic heavy metals in soil and edible and non edible parts of vegetables.