ABSTRACT
Heavy metals are a subset of elements defi ned weakly that exhibit metallic properties. They are “the most toxic inorganic pollutants which occur in soils” and can be of natural or anthropogenic origin. This group mainly includes transition metals, some metalloids, lanthanides and actinides. Many defi nitions have been formulated in terms of weight or atomic mass which leads to the periodic table, chemical classifi cation traditionally more solid and scientifi cally informative about elements; others have been based on the density and some of the chemical properties or degree of toxicity. However, the density or specifi c gravity is not of great importance in connection with the reactivity of a metal. It is important to note that this term has been applied even to semimetals (metalloids) such as arsenic,
1Planta Piloto de Procesos Industriales y Microbiológicos (PROIMI), CONICET, Av. Belgrano y Pasaje Caseros, 4000 Tucumán, Argentina. 2Facultad de Ciencias Naturales e Instituto Miguel Lillo, Universidad Nacional de Tucumán, Miguel Lillo 205, Tucumán. 3Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, Ayacucho 471, Tucumán. *Corresponding author: lbvilleg@hotmail.com
presumably due to the hidden assumption that “heaviness” and “toxicity” are in some way identical. This example further illustrates the confusion surrounding the term. For this reason “heavy metal” has been termed a “misinterpretation” by International Union of Pure Applied Chemistry (IUPAC) as a result of contradictory defi nitions and its lack of a “coherent scientifi c basis” (Duffus 2002, Bradl 2004).
