Characterization and remediation of contamination: the influences of mining and other human activities.

There are many definitions of the term contamination. Jefferis (2002 p. 75) provided the simple definition Bcontamination is a chemical, a living organism or energy in the wrong place.^ Paraphrasing this definition, contamination is the presence of an unwelcome component in a material, physical body, place, or other entity. In the natural environment, contamination implies that an exotic constituent that generally poses risks to biota living in that environment, particularly humans, has been introduced to the environment. Humans produce most contaminants, and cause many elements and compounds to be released into natural waters, soil, and the atmosphere that can then enter the human food chain. These elements and compounds are commonly called potentially harmful (or toxic) elements. Potentially harmful elements can have a very wide range of characteristics and origins. Potentially harmful elements can be heavy metals or metalloids (e.g., As, Cd, and Hg) released during mining or other industrial activities, or they can be organic compounds, such as medications (the excess of which can be released when they are used in clinical treatments). A very wide range of factors therefore affect contamination, and this variety affects the methods that are used to study and assess contamination processes and the methods that can be used to decrease the impacts of contaminants on the environment and human health. Some of the most important questions about contamination are related to the potential of potentially harmful elements to cause real health effects in the general population. Most contamination is caused by industrial processes, in mines and factories, for instance. However, the risks posed to workers in mines and factories are (or should be) generally controlled and minimized because they are known risks. However, improperly controlled gases and/or liquids containing potential contaminants can be released into the surrounding environment and affect local inhabitants. Potential risks need to be assessed taking into account processes that affect the mobilities and, in particular, the bioavailabilities of the contaminants present. Regional, national, and international regulators have introduced legislation in which maximum amounts of contaminants that can be released into the environment for any reason have been set. However, very limited success has been achieved in holding governments or individuals responsible for emissions of greenhouse gases, which are considered to be the primary causes of anthropogenic climate change (Zeben 2015). It is also necessary to take into consideration the chemical forms in which contaminants are released. For example, mercury is considered to be a potentially harmful element, but it is necessary to know which form of mercury is present in the environment or in a product that is released to assess properly the potential for mercury to cause toxic effects. The potential for toxic effects Responsible editor: Philippe Garrigues