The three-dimensional structure of humic substances and soil ...

It is expected that computational chemistry in combi-
nation with analytical pyrolysis (and analytical chemistry
in general) will play an important role in future studies
not only in environmental studies [14] and ecology [15]
but also in soil science [16] and agriculture as described
recently [13, 17].
Conclusions
(1) The molecular-chemical structure of soil organic mat-
ter is mainly determined by the inorganic soil matrix, the
climate, plant precursors, and the dynamics and specific
activity of biomass.
(2) The resulting three-dimensional, organo-mineral
complexes of decomposition products, biologically syn-
thesized materials and soil mineral particles can be ana-
lyzed indirectly by Py-GC/MS and directly by in-source
Py-MS.
(3) Analytical pyrolysis of humic substances and
whole soils yields a vast variety of pyrolysis products.
Their intra- and intermolecular chemical properties are
only understood when fast, reliable and powerful com-
puter-assisted data handling and evaluating allows the
chemistry to evolve in the three dimensions of space un-
der the precise structural parameters such bond lengths,
angles, and torsions, van der Waals forces, hydrogen
bridges, etc.
(4) To reassemble the identified chemical subunits to
a hypothetic structure of soil organic matter that reflects
as closely as possible the genuine status, above all con-
structive interdisciplinary work and collaboration is
needed.
Acknowledgements. The author is grateful for the financial support by
the Deutsche Forschungsgemeinschaft (projects Schu 416/3; Schu 416/
18-1) and the Ministry of Science and Technology, Bonn-Bad Godes-
berg, and the Umweltbundesamt, Berlin, Germany. Thanks are due to
R. Hempfling, R. Mt~ller, C. Sorge and H. Wilken (Fresenius Group)
and P. Leinweber, University of Osnabrack for their help and coopera-
73
tion. To work with the "pioneer of humic substances" Dr. Morris
Schnitzer, Agriculture Canada, Ottawa, has been and is a unique occa-
sion which gives its merits and rewards by itself.
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