Metal Ion Complexation by Soil Humic Substances

oil organic compounds that may form complexes with metal ions include: humic substances (HS), which represent the major natural organic fraction in soils; organic substances of defined molecular structure and chemical properties such as aliphatic acids, polysaccharides, amino acids, polyphenols, etc; and xenobiotic organic chemicals applied to soil accidentally or by purpose. The ill‐defined nature of HS and their component ligands, and the elusive nature of metal–HS interactions prevent metal–HS complexation reactions to be described in rigorous mathematical terms. In particular, the stability function concept provides an important overview and useful insights into the nature of metal binding by HS, and also may provide useful indications for most appropriate experimental methods in investigating metal–HS interactions. The chapter shows an overview of the spectroscopic techniques with the indication of the metal ions of application, the level of specificity of each technique for metal ion measurement, and its capability for qualitative and/or quantitative application.