Potentially toxic elements in the environment - a review of sources, sinks, pathways and mitigation measures

Pollution of ecosystems with potentially toxic elements (PTEs) has become a global problem with serious consequences for public health. The PTEs are hazardous to humans owing to their longevity, toxicity, and ability to accumulate in the biotic environment. As most PTEs cannot be degraded microbially or chemically, they can persist in soils for a long time. Besides posing a threat to landsphere, they may be transported to surrounding environmental spheres through movement of water, atmospheric circulation, and biological transmission. This can severely affect the ecological equilibrium. Accumulation of PTEs in soils pose serious health hazards to higher organisms leading to various diseases and disorders and significant relationships exist between the occurrence of PTEs and the toxic effects in humans. In natural soils, PTEs accumulate due to weathering of rocks and ores. Furthermore, locally or regionally significant accumulation of PTEs in soils may occur from industrial goods, pesticides and paints, municipal and industrial waste, fertilizer application, mining activities and atmospheric deposition. In response to the growing need to address PTE contamination, remediation methods have been developed employing mechanical, physico-chemical or biological based technologies. In this review, we discuss sources, sinks, pathways and mitigation measures related to natural and anthropogenic PTEs. We focus on As, Cd, Cr, Hg and Pb which are highly toxic and perform no physiological functions in biota. Further, these are the most widely studied PTEs.