High-molecular organic substances in soils

Using the methods of 13С-NMR and EPR spectroscopу we have studied the composition of humic substances in taiga zone, identified their principal functional groups and molecular fragments. The humic acid (HA) molecule is constituted of a nucleus formed by aromatic and heterocyclic rings. The nucleus is surrounded by periphery monosubstituted and twice-substituted aliphatic chains which are more hydrophilic than the nucleus is. Most HA functional groups are carboxylic and phenol-hydroxyl groups. Functional groups make HAs acid and able for cation exchange and complex formation.