Abstract:
In this paper are presented the preliminary results of studies
concerning the composition, structure and stability of organic-mineral
complexes from hortic anthrosols. The separation of organic-mineral
complexes has been performing by isodynamic magnetic method and by
extraction in aqueous Na2SO4 –polyethylene glycol two-phase systems. The
composition and structure of organic-mineral complexes have been studied
by Raman, FT-IR and UV-VIS spectroscopy, optic microscopy, thermal and
chemical analysis. In studied horthic antrosol, the content of organic-mineral
complexes varied between 20.42-48.36 % [w/w], being evidenced a relative
accumulation tendency in Ahok (48.36 %) horizon and in grain size fractions
< 0.002 mm (63.62-86.30 %, from total determined organic-mineral
complexes), respectively. The maximum weight (29.45-64.56 %) has been
observed at grain size fractions < 0.001 mm. The high apparition frequencies
and stability have organic-mineral complexes which include in their
structures predominantly, the amorphous forms of clay minerals and of iron
oxi-hydroxides. In function of clay mineral type from organic-mineral
complexes composition, have been observed that the apparition frequency
and stability follow the order: smectite > illite >> kaolinite (have been
evidenced a special stabilization effect in case of Ca and Mg forms of clay
minerals). In function of iron oxi-hydroxides type from organic-mineral
complexes composition, has been observed that the apparition frequency and
the stability follow the order: Fe(OH)3 (amorphous) > Fe(OH)3 (ferihidrite,
amorphous) > -FeO(OH).nH2O (lepidocrocite) > -FeO(OH).nH2O
(göethite) > -Fe2O3 (hematite). The separated and studied organic-mineral
complexes have very complex compositions and structures (generally have 4-
5 structure levels), include over 65 % from mineral and organic components
of anthrosol and are behaves as supra-molecular assembles very stable and
with a high chemical-structural flexibility degree. In function of chemicalmineralogical composition and of their structure, the organic-mineral
complexes from studied anthrosol have been classified in four main classes.
