Potentially toxic metals pools

Figure 9.2 Potentially toxic metals (PTMs ) pools of different mobility, target organisms and routes of transfer in and from the soil.

Table 9.2 Examples of extractants and presumed extracted pools of plant-available potentially toxic metals (PTMs) in soil...

In this context, speciation science seeks to characterise the various forms in which PTMs occur in soil or, at least, the main metal pools present in soil. Understanding speciation is important for assessing the potential of soil to supply micronutrients for plant growth or to contain toxic quantities of PTMs, and for determining amelioration procedures for soils at risk of causing the PTMs contamination of waterways. The residence time of an element in a soil depends on the mobility of its predominant forms. Speciation science is relevant to scientists with many different backgrounds and should be taken into consideration by legislators in the field of environmental protection. 

In aquatic environments, more research is needed on the chemical speciation of silver to evaluate risk to the organism and its consumers. Most silver criteria formulated for the protection of aquatic life are now expressed as total recoverable silver per liter. But total silver measurements do not provide an accurate assessment of potential hazard. Silver ion (Ag+), for example, is probably the most toxic of all silver chemical species and must be accurately measured in the assessment of silver risks in aquatic environments, perhaps as acid-soluble silver. Little is known of the biocidal properties of Ag + andAg + that are the active ingredients in disinfectants and used increasingly in water purification systems of drinking water and swimming pools. The effects of these silver species on organism health clearly must be researched. Silver interactions with other metals and compounds in solution are not well defined. For example, mixtures of salts of silver and copper markedly increased the survival of oyster embryos, but only when... 

Lead is the most recycled metal, for several reasons It is too toxic to go to landfills the major use is in automobile batteries, which have a predictable life span and used batteries are collected at legally designated locations in most states. Iron and steel are second in percentage recycled, most of which is recycled within the industry rather than from consumer products. Iron and steel are used in vastly greater quantities than all other metals combined, resulting in a huge pool of scrap to be dealt with. Not recovering it would be a financial as well as an environmental burden. Also, all steel is potentially recyclable without separation of pure metals from the mixture. 

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