On the chemical structure of humic substances in soils

Humic substances are present in real soils as a nonvalently and valently bo und ensemble that belongs to a group of spatially structured systems, in wh ich the heterogeneity of adsorption surfaces of secondary minerals is assoc iated, in a complicated manner, with the heterogeneity of organic macromole cules and intra- and intermolecular links. An indefinite multitude of possi ble macromolecular conformations of humic substances can correspond to the minimum of free energy in the whole structured system.