Chapter 9 - Chemical Speciation to Assess Potentially Toxic Metals' (PTMs') Bioavailability and Geochemical Forms in Polluted Soils

Abstract

Abstract Potentially toxic metals (PTMs) are persistent contaminants in the soil environment. The simple determination of their total or ‘pseudototal’ content in soil might minimise the risks for biota and human health, assuming that pollutants transferring to water resources or biota are simply correlated with contamination level. In contrast, relevant paradigms in environmental monitoring, risk assessment and remediation feasibility are the PTMs' mobility and bioavailability to microorganisms, plants, animals and humans. For a correct assessment of risk/toxicity (according to PTMs' content and availability) of a polluted soil and to predict its reduction 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 methods and strategies that provide information on the dynamics and behaviour of PTMs in soil. Speciation science seeks to characterise the various forms in which PTMs occur or, at least, the main metal pools present in soil. This chapter provides a review of the single and sequential chemical extraction procedures that have been more widely applied to determine the plant and the human bioavailability of PTMs from contaminated soil and their presumed geochemical forms. Examples of complementary use of chemical and instrumental techniques and applications of PTMs' speciation for risk and remediation assessment are illustrated.