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

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HA 3 D version demonstrates the flexible network with voids and hollows which offer binding and trapping of biological and anthropogenic molecules [2]. Further- more, long-continued calculation periods (> 6 days) give energies in the order of 608 kJ 0.1 nm-1 mol-1 and gra- dients
70 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
Page 1 and 2: Fresenius J Anal Chem (I995) 351:62
Page 3 and 4: 64 Table 2. Aromatic compounds char
Page 5 and 6: 66 (CH3)o-3 (CHs)o-2 0 ~ @O ~ (CH3)
Page 7: 68 ergy of the molecular system was
Page 11 and 12: 72 Fig. 10b \ Fig. 10c

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

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