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

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Fig. 9. Result of atrazine transport into the 3 D structural model of an organo-mineral complex in soil with atrazine trapped in the voids (V)
the atrazine molecule moves with decreasing energy and
increasing conformational stability step-by-step more
into the available space of the void. Finally, arriving with
the geometry optimization and energy minimization
close to a total energy of 10008.21 kJ nm -1 mo1-1 and a
gradient of 0.37 kJ nm-1 mol-t, the atrazine molecule is
immobilized in the void by formation of a hydrogen bond
from H (21, molecule I) to a HA carboxyl group of II (O
(606, molecule II)) which is an integral part of the
organo-mineral particle V now. Figure 10c shows the
space requirements of the atrazine molecule in the hollow
space, but also, may be more important, how much space
is left for chemical decomposition reactions.
Nanochemistry
For the biological and chemical reactivity of the trapped
anthropogenic compound it is highly interesting to deter-
mine exactly the distances between I and the surrounding
molecular complex of the HA II and the silica matrix IH.
As derived from Fig. 10a, the numbered atoms and
Fig. 10b the atoms labelled by element symbols, some