The
form of element in
soil is determined not only by the
characteristics of elements, but also by the condition of
regional physical geographical, especially the type and the characteristics of soil. The characteristics of Pb form in 10 main soil types in China show that the relative con-tents of each form of Pb in various soil types is mostly oxide iron-manganese form Pb>carbon-ate or weak conbination form Pb^organic-sulfur compound form Pb>exchange form Pb>solu-tion in water form of Pb. This shows, to a most degree, that the disposition of composition each other form of Pb in various soil type is determined by the chemical properties of Pb element. The relative contents of solution in water form of Pb and exchange form of Pb trend toward de-creases from
south to
north and from east to west with the order of distribution of soil geograph-ic zone. This shows their characteristics of regional
differentiation with the distribution of soil geographic zone. The carbonat form of Pb increases form of Pb that are comparatively difficult to migration in north soil, and the weak combination form of Pb increases form of Pb that are comparatively easy to migration in south soil and east soil. Both of them increase the extent of regional differentiation Pb form or activity of Pb between south and north.The oxide iron-manganese form of Pb also trands toward regional differentiation from south to noth and from east to west, else than laterite that is special cause, only that it don't increase, but it decreases. The organic-sulfur form of Pb trend toward decreasing from east to west, but it trend toward decreasing only from central setion to north. This is caused by differentiation oforganic contents in various type soils.In all soil, the largest coefficient of differentiation of Pb form is the solution in water formof Pb. exchange form of Pb. and solution in water-I-exchange-j-weak conbination form of Pb. Their coefficient of differentiation change among 1~ 1 places, but the oxide of iron-manganese form of Pb and organic-sulfur form of Pb change only among in unit's place. Therefore. 3 in front form of Pb is main form of Pb to evaluate regional differentiation of form of Pb in soil.
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