Models of Humic Structures: Association of Humic Acids and Organic Matter in Soils and Water

Terrestrial humic acids (monomer, oligomer, and polymer) and soil organic matter (SOM) as well as dissolved organic matter (DOM) were investigated by model design and computational chemistry. Molecular mechanics calculations were used for geometry optimization and determination of total potential energy, bond-, angle-, dihedral-, van der Waals-, stretch-bend-, and electrostatic energy derivatives and, tentatively, association energy. Atomic and molecular properties such as weight, surface, volume, specific surface, density, thickness, space-requirements, dipole moment and moments of inertia were calculated at nanochemistry level. For natural organic matter (NOM) are of particular interest: (i) the aromaticity of the systems; (ii) the polarity and reactions with polar biological molecules, xenobiotics and water; (iii) the type and strength of bonds, attraction and repulsion; long-range and short-range forces; and (iv) the formation of SOM and DOM oligomer models. The evaluation of energy differences in the generated terrestrial and aquatic colloids were evaluated during the formation of association complexes at the atomic and molecular level in the range between approximately 0.05 and 40 nm.