Heavy Metals, Metalloids, Their Toxic Effect and Living Systems

Abstract

Pollution of the biosphere by heavy metals is a global hazard that has accelerated since the beginning of the industrial revolution. Toxic heavy metals are harmful to living organisms even at low concentrations whereas heavy metals that are essential trace elements are required by plants at low concentrations but can become toxic at high concentrations. Heavy metals released from different sources accumulate in soil and, where bioavailability is high enough; can adversely affect soil biological functioning and other properties, leading to the loss of soil and ecosystem fertility and health. It is important that heavy metal contaminated sites are remediated as heavy metals do not decompose into less harmful substances like organic contaminants, and thus are retained in the soil. In this review, we survey and analysis our current knowledge and understanding of the abundance of heavy metals in soil, their phytoavailability, their toxicity, their uptake and transport, role of rhizobia and other microbes and overall rhizosphere processes.