The color of both gleyic and non-gleyic loamy cryogenic soils of the Kolyma lowland expressed in highly informative optical system CIE-L*a*b* does not show significant difference. In order to raise effectiveness in distinguishing gleyic and non-gleyic soils/horizons all samples were treated with 30-40% H₂O₂. Two parameters have been used: 1) increase in redness after H₂O₂ treating; 2) the degree of lighting related to organic carbon content “Light” = (L_H2O2 – L_initial) / (1 + lgCorg). The iron in oxalate (Fe_o) and dithionite (Fe_d) extracts have been measured. Mössbauer spectroscopy also was used to estimate possible mineral composition and the Fe³⁺/(Fe³⁺+ Fe²⁺) ratio for initial and H₂O₂ treated samples.

Non-treated samples of Cryosols have low reddishness: a* < 2. Most of samples from B, Bg and G horizons showed slight decrease in redness after H₂O₂ treating, thus the greenish elements of color increase: 0 > Δa* > -1. The humus of soils being investigated is raw and hardly oxidized: the “Light” value is low (2-9). Hydromorphism development leads to higher degree of organic matter oxidation: in B horizon “Light” value=2-5 and for Bg and G horizons “Light”=5-9. The whole data show inverse relation between Δa* and “Light”.

The composition of Fe combinations in soils of various degree of hydromorphism was estimated using two chemical criteria: Fe_o:Fe_d (Shwertmann criteria) and content of biologically reducible iron: Fe=0,19 Fe_o-0,028 (Fe_d - Fe_o) (empirical criteria by Van Bodegom obtained in experiments on biological reduction of various soils from East Asia, East Africa, Europe and USA - Van Bodegom et al, 2003). Both criteria are able to distinguish B horizons from Bg and G, but Van Bodegom's criteria is more effective. The most effective differentiation of gleyic and non-gleyic soils was estimated in the following coordinates:  “Light” – reducible Fe.

Mössbauer spectroscopy of selected samples showed that most of total iron in gleyic and non-gleyic soils is contained in silicates. The amount of hydroxides free iron is rather low.

Samples from Kolyma Cryosols showed low degree of oxidation Fe³⁺/(Fe³⁺+ Fe²⁺)=0,48-0,60 in comparison to samples of loamy soils from European territory of Russia where oxidation degree reached 0,85-0,95. This fact alongside with estimated absence of hematite (αFe₂O₃) and only some amount of dispersed hydroxides is evident for weakly expressed Fe oxidogenesis (oxides formation).

It has been found that H₂O₂ treatment of Kolyma soils with high content of silicate's Fe²⁺ results in partial Fe oxidation unlikely to European loamy soils with high content of iron hydroxides where H₂O₂ acts as a Fe reducer.

Gleyic and non-gleyic soils are clearly divided using simultaneously trans-Fe³⁺ /( trans-Fe³⁺ + cis-Fe³⁺) ratio and Fe_o:Fe_d ratio. Gleyic samples have much higher Fe³⁺ saturation of trans positions and higher Shwertmann criteria in comparison to non-gleyic B horizons. The trans-Fe³⁺ /( trans-Fe³⁺ + cis-Fe³⁺) ratio in gleyic horizons reached 0,72 and in non-gleyic (B) horizons was equal to 0,55. We propose the following mechanism for this phenomenon: Fe³⁺ mobilization and introduction in trans positions in silicate's lattice which results in shift to the green part of spectra. Thus Fe³⁺ is not completely removed from the horizon or just reduced in situ to Fe(II)-minerals but partially introduced in silicates.

It is evident that new data on Mössbauer spectroscopy demands new interpretation of oxalate- and dithionite-extractable Fe in Cryosols of the Kolyma lowland. The estimated high content of free Fe₂O₃d >1% in Bg and G horizons contradicts with Mössbauer spectroscopy data which is evident for small amount of Fe₂O₃d. It seems that CBD and oxalate extract iron of silicates. Thus Fe_o:Fe_d ratio in Kolyma's loamy soils is much more about Fe-silicates composition than of amorphous to free iron relation. Nevertheless de facto Fe_o:Fe_d ratio effectively works for distinguishing of gleyic – non-gleyic soils.