A review on heavy metal pollution, toxicity in agricultural soil and remedial measures

Soil heavy metals (some metals and metalloids possessing biological toxicity, such as lead, chromium, arsenic, zinc, cadmium, copper, mercury and nickel) pollution has become a worldwide environmental issue that has attracted significant public attention, mainly from the rising concern for the security of agricultural products. Soils are receiving terrific amount of pollutants from the various sources and these heavy metal contamination in agricultural soil may impart functional disorders of soils, retarded plant growth and even harm the health of soil organisms and humans through contamination of food chain. These heavy metals or metalloids do not undergo chemical and biological degradation and remaining in the soil for longer duration and enter the agro- ecosystem through natural process and anthropogenic activities. Among the remediation using physical, chemical and biological methods, Phytoremediation has proven to be a promising demonstrated available technology to conventional approaches to solve the problem due to its cost effectiveness, aesthetically pleasing and environmental friendly nature. However further comprehensive multidisciplinary researches integrating with biotechnological approaches are needed to improve plant tolerance and minimizing the accumulation of toxic metals in soils. Remediation of heavy metal contaminated soils is necessary to reduce the associated risks, make the land resources available for agricultural production, scale down land tenure problems and enhance food security. This review emphasizes on the sources of heavy metals in soil and remediation technologies involved in their removal from the soil.