A new approach to the structural analysis of humic substances in water and soils - Humic acid oligomers

For humic acid (HA) oligomers in water and soils, a novel three-dimensional structural concept is developed which is based on comprehensive investigations combining geochemical, wet-chemical, biochemical, spectroscopic, agricultural and ecological data with analytical pyrolysis. Direct temperature-programmed pyrolysis in the ion-source of the mass spectrometer combined with soft ionization in very high electric fields (Py-FIMS) and Curie-point pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) are the principal analytical methods for the proposed humic acid monomer and oligomers (n = 1-15) with molecular masses in the range of 5,500 to 84,600 g mol(-1). Emphasis is put on molecular modeling and geometry optimization of humic complexes using modern PC software (HyperChem) in order to determine low energy conformations, space requirements, voids, as well as inter- and intramolecular hydrogen bonds. The dynamic process of developing an optimal conformation of geomacromolecules can be observed and controlled at nanochemistry level. Strategic ecological aspects for the prediction and molecular-chemical explanation for binding and trapping of biological and anthropogenic substances and inorganics such as heavy metals are put forward.