Bioavailability of Heavy Metals in Soils and their Uptake by Paddy (Oryza sativum) – An Empirical Study

Abstract

Heavy metals, such as Cadmium, copper, lead and chromium are the most toxic, persistent, and widespread environmental pollutants, particularly in areas with high anthropogenic pressure. Dissolved or suspended metals in soil and water, even in traces can degrade water quality and soil fertility and become available to plankton, nekton which in turn alters the normal biogeochemical cycling. Crop plants growing on heavy metal contaminated medium can accumulate high concentrations of trace elements which cause serious health risks to consumers. The toxicity of heavy metals at high levels of exposure is well known but a major concern is the possibility that continual exposure to relatively low levels of these heavy metals through the consumption of the vegetables and food crops may entail adverse health effects. Only bioavailable metals in soil are able to exert toxic action. Bioavailable metals cannot be measured directly through chemical analysis-only living organisms determine bioavailability. An experimental study was carried out to better understand the bioavailability and extent of toxicity of heavy metals on the growth of paddy plant in the heavy metal contaminated soil samples of Ranipet industrial area. Results show that Chromium and Zinc were recorded in higher concentration in all the four study areas. The heavy metal Cr concentration was in the order MGR Nagar > Vannivedu > Bharathi Nagar >Vanapadi. Germination studies of Oryza sativam in the metal contaminated soil medium was carried out with the finally extracted soil and the germination time and extent of growth were studied. The result reveals that the percentage of seed germination is in the order Bharathi Nagar (90%) > Vanapadi (75%) >MGR Nagar (55%) > Vannivedu (50%) respectively.