Stabilization of organic matter in soil by complexation is the link between metal cation and anion from the organic matter.
Considering the various forms of free iron in soils: are the most crystallized forms of free iron (geothite and lepidocrotite, not the Fe cristallized to silicate) available for the formation of organo-mineral associations ? Should it first by altered to Fe2+ or Fe3+ depending on the edaphic conditions (pH and redox potential) ?
And what about the amorphous forms of iron in soils ?
Metal sorption to diagenetic iron and manganese oxyhydroxides and associated organic matter: Narrowing the gap between field and laboratory measurements
Author links open overlay panelA.Tessier1D.Fortin2N.Belzile3R.R.DeVitre1G.G.Leppard4
Dear Sarah Smet,
I am not an expert, but Georg Guggenberger and Robert Mikutta are. See also some of their publications:
Article Sorptive stabilization of organic matter by microporous goet...
Article Organic matter bound to mineral surfaces: Resistance to chem...
Best regards
Nils
Dear Sarah Smet,
Generally, the interaction between crystallized oxyhydroxides of iron with organic matter occurs through adsorption processes. The extent of adsorption will depend on many factors such as charge on the cation (iron mineral), specific surface area, and also on the prevailing conditions (pH, redox potential, and presence of competing cations). Another important factor to consider is the nature of the mineral (crysyallized or amorphous).
The two references provided above by Nils Borchard are informative. I am also adding another which can help you with experimentation.
Considering the specific case of amorphous iron interaction with organic matter, very early studies have shown that the identification of amorphous iron oxides in soils, which has often been based on a sharp exothermic peak at about 320°C on D.T.A. records was due to the organic matter present. For details on this, see the paper by Taylor (1959) – "AMORPHOUS IRON OXIDES IN SOILS"
link: https://doi.org/10.1111/j.1365-2389.1959.tb02352.x
Best regards,
Georges K Kome.
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