In the soil environment potentially toxic metals (PTMs) are persistent contaminants. The common determination of their total or “pseudototal” content in soil might minimize the risks for biota and human health, assuming that contaminants transferring to water resources or biota are basically correlated with contamination level. In contrast, relevant paradigms in environmental monitoring, risk assessment and remediation feasibility are the PTMs mobility and availability to microorganisms, plants, animals and humans. For a proper assessment of risk/toxicity of a polluted soil and to predict its attenuation after application of remediation techniques it is crucial to establish the speciation, mobility, and biogeochemistry of the contaminants. In this sense, a requirement exists for analytical methodologies and strategies providing information on the dynamics and behaviour of PTMs in soil. Speciation science seeks to characterise the diverse forms or, at least, the main metal pools in which PTMs are present in soil. This chapter provides a review of the single and sequential chemical extraction procedures that have been widely applied to determine the plant bioavailability and the main geochemical forms of PTMs from contaminated soil. Complementary use of chemical and instrumental techniques and applications of PTMs speciation for risk and remediation assessment are illustrated.
Keywords: soil pollution, heavy metals, speciation, sequential chemical extractions, risk assessment