Conceptual Delimitation of Heavy Metals in Environmental Science

Roxana Vidican, Tania Mihăiescu, Anca Pleșa, Ioana Crișan

Abstract


Heavy metals have been used by humans for thousands of years. Since ancient times lead was used for pottery glazing while mercury was attributed medicinal properties. Awareness of the danger that heavy metals pose for environment and human health has been gradual. Soils normally contain almost the full range of heavy metals, originating from lithogenic source and from anthropic activity. The first use of the term “heavy metals” in scientific context dates back to 1936. In time has been used as broader concept including elements that cannot be classified as metals or even metalloids. Most definitions given in the past took into consideration only one criteria at a time in defining “heavy metals” and since 1980 many scientists expressed their dissatisfaction for the imprecise delimitation of the concept. Based on a three-way criteria a comprehensive definition limits “heavy metals” to a category of elements that concomitantly are: natural occurring metals, have atomic number >20 and elemental density >5 g/cm3. Based on this definition 51 elements from periodic table can be considered “heavy metals”, excluding some such as: Al, As, Se, Ti. Over 20 heavy metals are recognized for the serious health conditions they can induce in humans. Given the increasing pollution in last century, policy efforts are directed towards preventing and limiting heavy metals contamination of the environment, drawing thresholds and requiring remediation.


Keywords


pollution, metalloids, toxicity, health, remediation.

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