Potentially toxic metals affecting factors

Figure 9 3 Major plant and soil factors affecting plant-available potentially toxic metals ...

Chemicals, which are persistent, toxic and liable to bioaccumulation, are called PTBs. They have primarily local effects. Persistence is the evidence that the substances half-life is greater than two months in water and greater than sue months in soil or sediment. Toxicity is the potential to adversely affect human health and/or the environment. Bioaccumulation is the evidence that the Bio-Accumulation Factor (BAF) is greater than 5000. Up to 1995, there was no clear definition of which products belong to this class [394]. Heavy metals, such as mercury and POPs fall into this category. 

Equilibrium models are widely used in assessments of trace metal bioavailability, toxicity, and transport through the environment. Properly applied, equilibrium models are powerful tools in such assessments. Due to a variety of factors, however, equilibrium modeling often falls short of its full potential. One problem, of special importance in equilibrium characterizations, is simplistic modeling. The use of simplistic chemical models is particularly important because it affects not only the modeling of complex natural systems, but also modeling of relatively simple chemical media used to generate primary thermodynamic data. 

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