A heavy metal is any metal or metalloid of environmental concern. The term originated with reference to the harmful effects of cadmium, mercury and lead, all of which are denser than iron. It has since been applied to any other similarly toxic metal, or metalloid such as arsenic, regardless of density.
The high toxic and persistent nature of heavy metals in the environment has made heavy metals priority pollutants. For good environmental management an understanding of the changing concentration and distribution of heavy metals and their compounds in various compartments of the environment is of the essence. Several workers have investigated the concentration of heavy metals in the coastal rivers with Atlantic tidal effect in Nigeria. The indiscriminate discharge of effluents by the petroleum companies into the environment constitutes one of the main factors of degradation of the aquatic and terrestrial ecosystem located near major urban centers and contributes to the increase of the concentrations of heavy metals in this environment. The monitoring of heavy metals in the environment is fast becoming an essential aspect of pollution study. The lack of natural elimination processes for metals aggravates the situation. As a result, metals shift from one compartment within the aquatic environment to another including the biota often with detrimental effects, through sufficient bioaccumulation. As a result of adsorption and accumulation, the concentration of metals in bottom sediments is expected to be higher than in the water above and this sometimes can cause secondary pollution problems. This is why bottom sediments are repository of heavy metals. Heavy metals are of considerable environmental concern due to their toxicity and cumulative behavior.
Last date updated on June, 2014