Composition of Iron Compound Groups in the Russian Taiga and Tundra Permafrost Soils

The composition of iron compounds in the permafrost-affected soils of tundra and taiga landscapes of Russia is examined. The total iron content is measured using X-ray fluorescence method. Soil chemical, physicochemical, and physical properties and the concentrations of silicate, nonsilicate, crystallized, and organic matter–associated iron compounds are studied with the help of conventional methods. The studied soils are classified as cryometamorphic (Haplic Cryosols), cryozems (Turbic Cryosols), peat cryozems (Histic Turbic Cryosols), gleyzems (Reductic Gleysols), peat gleyzems (Histic Reductaquic Cryosols), podzolic soils (Albic Retisols), and soddy podburs and podzols (Entic and Albic Podzols). The depth of permafrost table in soils varies from 0.3 to 1.7 m and deeper. On average, the total iron content amounts to 1.2–4.5% with the maximum of 10.2%. Silicate compounds account for up to 85% of the total iron because of a poor pedogenic transformation. The content of nonsilicate iron does not exceed 1.2%; its increase morphologically appears in the upper mineral soil horizon and in landscapes on the slopes as rusty red mottles and interlayers. This correlates with increased values of the lateral differentiation coefficient, ranging from 1.1 to 2.3. The suprapermafrost horizons at depths down to 1 m accumulate nonsilicate iron compounds; the concentrations of crystallized and organic matter–associated compounds amount to 0.6–0.8 and 0.2–0.4%, respectively. Presumably, this is associated with the organic matter accumulation, sorption on soil clay particles, and reducing conditions above the permafrost.