The Influence of Natural and Synthetic Ligands on the Transport and Function of Metal Ions in the Environment

The environmental effects of coordination compounds are discussed from the point of view of the introduction of unnatural levels of metal ions and ligands into various parts of the ecosystem. The transport of toxic metals, with special reference to mercury, lead, and cadmium, is described, and the available information on the nature of these metals as they exist in the environment is examined. Consideration is given to the occurrence, constitution and properties of natural ligands in the environment. As a guide to the introduction of excessive ligands into the environment, the properties and uses of the ligands now in large scale commercial production are examined. Applications of EDTA, NTA, and sodium tripolyphosphate, all of which are used in large amounts, are considered in detail. An analysis of the current controversy over the substitution of NTA for tripolyphosphate in detergents indicates that NTA should be favoured for this large scale application and that the environmental impact of NTA should be minimal.