Role of Potentially Toxic Elements in Soils

There are numerous sources of toxic elements in soils. In naturally occurring soils they can accumulate during weathering of rocks. Background concentrations in soils are thus determined by the concentrations in the underlying parent materials. Most toxic elements in soils exhibit strong adsorption by clays. Under certain conditions, small portions become soluble. Humans cause accumulation of toxic elements in soils from different sources. They are common in industrial goods, as components of paints and pesticides, and as a constituent of land influenced by municipal and industrial waste or by mining activities. Trace elements have been added to soils by applying fertilizers and from atmospheric deposition. A significant relationship exists between the presence of toxic elements and the incidence of some serious human diseases. Toxic elements may enter the human body through inhalation of dust, direct ingestion of soil and water, dermal contact of contaminated soil and water, and consumption of vegetables grown in contaminated fields. They are known to be persistent in the human body and can lead to a wide range of toxic effects. Specific antidotes exist for treatment of intoxication. For remediation of contaminated soils, a number of technologies have been developed mainly using mechanically, physico-chemically or biologically based methods. In this chapter, sources of toxic element contamination, toxic element speciation, transformation and transport behavior in soils, bioavailability, and the associated environmental and health risks, medical treatment and mitigation options are discussed.