The three-dimensional structure of humic substances and soil organic matter studied by computational analytical chemistry

A novel three-dimensional structural concept for humic substances and soil organic matter (SOM) is proposed which is based on previously published, comprehensive investigations combining geochemical, wetchemical, biochemical, spectroscopic, agricultural and ecological data with analytical pyrolysis. Direct, temperature-programmed pyrolysis in the ion-source of the mass spectrometer and soft ionization in very high electric fields (Py-FIMS) and Curie-point pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) were the main applied thermal methods. Emphasis is laid on molecular modelling and geometry optimization of complex, polydisperse structures of biomacromolecules using modern PC software (HyperChem^®). Trapping and binding of atrazine in an organo-mineral complex is introduced as a first example of simulation experiments for soil processes at atomic level (nanochemistry). Future applications of semi-empirical calculations and molecular dynamics in pyrolysis studies are outlined.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday