An overview of heavy metal stress in soil ecosystem and technological intervention for its remediation

With the advent of industrialization and modernization in agriculture to feed the increasing population, there has been negative effect on environment and human health. Among all kinds of pollution, heavy metal pollution is significant in soil ecosytem and are hazardous contaminants of environment, which pose detrimental effect on human health and listed as priority pollutants by United State Environmental Protection Agency (USEPA). Lead (Pb), Mercury (Hg), Arsenic (As) and Cadmium (Cd) are ranked 1st, 2nd, 3rd and 6th respectively in the list of US agency for toxic substances and disease registry. Concentrations of these toxicants in human and animal body increases many fold through bio magnification and causes serious health problems in human viz. biological defenses, intrauterine growth retardation, impaired psychosocial faculties, disabilities associated with malnutrition, decreased immunity and high prevalence of upper gastrointestinal cancer. Thus, there is an urgent need of preventive and/or curative measures to decrease the flow of heavy metals in food chain of human beings. But, the process of modernization and industrialization could not be avoided as they are integral part of development. Therefore, we have to think for sustainable way to reduce the impact of these heavy metals on environment and in this process, there are various technological intervention such as use of natural sorbents e.g. vermicompost, sawdust, farm yard manure; phytoremediation process by using hyperaccumulator plants; use of chelating agents that binds with heavy metal owing to property of chelation; biotechnological tools and recently developed nanotechnology which has exceptional adsorption and high surface area unique mechanical and electrical property with high chemical stability which is attracting attention of research for remediation of heavy metals from contaminated ecosystem. Objective of this paper is to briefly overview the heavy metal stress in soil ecosystem, their possible sources, movement through food chain and sustainable remediation strategies.