Chapter 12 - Transfer of Heavy Metals and Radionuclides from Soil to Vegetables and Plants in Bangladesh

Abstract

Current research has been focused on the transfer of heavy metals (Fe, Pb, Co, Cd, V, Cu, Mo, Ni, Cr , Mn, Zn, As, Sr, Hg,) and radionuclides (40K,232Th,226Ra,238U and 137Cs) from soil to vegetables and plants in terms of transfer factor which is commonly used to estimate the food chain transfer of these elements and possible phytoremediation. Wide varieties of vegetables and plants and associated soils were collected from various regions of Bangladesh under actual field conditions. Contamination levels of the elements was measured and the Health Risk Index (HRI) and Plant Transfer Factor (PTF) of these elements from soil to vegetable/plant were calculated. Results reveal that there is a substantial build up of heavy metals (Mo, Sr, Fe, Cd, V, Cu, Ni, Cr , Mn, Zn , As) pollution in the soil of Bangladesh which varies with location depending on the sources. In addition, heavy metal (Fe, Sr, Ni, Zn, Cr, Mn, Pb, Cd ) content in plants grown near the industrial area showed higher values than in the non-polluted area and also exceeded the world average soil data. The HRI for heavy metals in the plants showed the order Mn > Fe > Cr > Pb > Zn > Cd > As where unsafe HRI values were found for Fe, Pb and Zn in Abelmoscus escultant and leafy vegetables indicated health risks associated with the ingestion of these contaminated vegetables to the inhabitants. The PTF value for heavy metals varied greatly with plant species and also with sampling location. A higher PTF value (0.4–4.5) was found for Mn, Zn, Cu in Enhydra fluctuans, Zea mays, Nephrolepis exaltata and Oryza sativa which could be used for phytoremediation of these metals from the contaminated soil. Conversely, the TF of the radionuclides were found in the following order: 40K > 232Th > 226Ra > 238U whereas 137Cs was not transferred. The higher TF found in the study for all the natural radionuclides indicates that the area is a high background radiation area (HBRA) and radiologically unsafe to the inhabitants due to the harmful effects of ionizing radiation from natural radionuclides in soil.