ABSTRACT
Element Distribution Mapping .................................................................. 470 25.4 Exploring Ligand Environment of Metals in Plant Tissues.................................................. 471
25.4.1 X-ray Absorption Spectroscopy ................................................................................ 472 25.4.1.1 Basic Principles .......................................................................................... 472
The origin of naturally occurring metals is in rocks, soils and sediments, where they are primarily trapped in stable, insoluble forms. Yet, through natural processes small amounts of metals can be mobilized and allowed to circulate in water, soil and air, through biogeochemical cycles that keep distribution of any given metal within an ecosystem at relatively constant concentrations over time. Their constant cycling is especially important for the biosphere, since certain amounts of metals are essential for organisms, but can be highly toxic when present in excess. With mining of ores, in addition to smelting and other puri—cation practices, metals have been rapidly released from their more stable insoluble forms to less stable, soluble forms and released into the environment. So now days metal contents released into the environment by anthropogenic activities highly overwhelm natural biogeochemical cycles (Singh 2005).
