Radial Differentiation of Chemical Composition of Cryogenic Soils in the Chara River Valley, Northern Transbaikalia

The subject of the study is represented by the content of iron compounds and their radial differentiation in the profiles of cryogenic soils of the Chara River valley (northern Transbaikalia). The studied soils are assigned to postpyrogenic permafrost gleyzems, and the depths of the seasonal active-layer in them are from 34 to 44 cm. Macronutrient concentrations, with the exception of Si, rarely exceed 5.0%, while the silicon content reaches 24.3%. Silicon is also characterized by removal from the upper part of soil profiles and accumulation in permafrost soil horizons. The highest concentrations of a significant part of macroelements are typical for the O horizons (4.8 for Mg and 1.5 mg kg–1 for Ca). Trace elements Sr and Zr are distributed the most contrastingly (from 5.0 to 29.7 and from 5.6 to 47.1 mg kg–1, respectively). Values of coefficient R from 0.3 to 0.9 indicate the initial stage of postpyrogenic restoration of soil properties, and the intensive accumulation of Mg, Ca, Ti, Fe, Sr, and other elements in the upper part of oxidized-gley permafrost gleyzem is evidence of active restoration. The soils consists of about 3.4% iron, which is more than 60–75% composed of the silicate group of compounds (Fes). The moisture content of soils and the prevailing reducing medium conditions contribute to the formation of monotonous distributions of elements in their profiles; and in soils without signs of stable hydromorphism, permafrost horizons contain almost twice as much Feox and Feextr.