Distribution of many minor elements depends very much on their state of oxidation. Fe, Mn, and Co are often immobilized by oxidation; S, Se, As, Va, Cr, Mo, and W may be mobilized. Biochem. processes participate in these processes. Certain peculiarities, such as the conc, of a large number of rare elements in forest litter, are due to special biogeochemical processes. Modern geochemistry demonstrates that the same rules apply to the distribution of all elements, whether major or minor.