Abstract: The study's focus is on the distribution of oxygen and hydrogen isotopes in the ice cores of frost blisters in the Chara River valley, Transbaikalia. The Kodar and Udokan mountain ranges surround the Chara Depression. Cryogenic (frosty) heaving is common in high humidity areas with loamy, clay, and peaty sediments. In summer 2023, the authors described two seasonal frost blisters in swampy, forested depressions on the periphery of the Charsky Sands (in the so-called thermosuffusion funnels). Oxygen and hydrogen isotopic compositions of oxygen  (δ18O) and hydrogen (δ2H) in blister ice were analyzed. It has been established that seasonal frost blisters are formed mainly due to downward freezing of the water-saturated active layer sediments, but in some cases, ice was formed as well due to upward freezing from the lower boundary of the active layer. The vertical distribution of the isotope values, as well as the δ2H-δ18O ratio in ice, indicates a relatively rapid freezing of water in closed system conditions during one cycle of freezing. In the ice layers sampled horizontally, very similar isotopic composition values were obtained (for example, in blister ice 1, δ18О values ranged from –17.51 to –17.32‰), which indicates consistent horizontal freezing of ice layers. The slopes of the δ2H-δ18О ratio lines for blister ice are 5.82 (blister ice 1) and 5.95 (blister ice 2). A decrease of the δ2H and δ18О values of blister ice on frost mounds with depth and a slope of the δ2H-δ18O ratio line less than 8–7.3 indicates water freezing under closed system conditions during one cycle without moisture inflow. The distribution of isotopic values in the blister ice of seasonal frost mound 2 may indicate simultaneous bilateral freezing of the water volume.

Abstract: The subject of the study is the content of iron compounds and their radial differentiation in the profiles of cryogenic soils of the Chara River valley (Transbaikalia). The studied soils belong to post-pyrogenic permafrost gleyzems, the depths of the seasonal active‐layer of these soils are from 34 to 44 cm. Macronutrient concentrations, with the exception of Si, rarely exceed 5.0%, while the silicon content reaches 24.3%. Si is also characterized by removal from the upper part of soil profiles and accumulation in permafrost soil horizons. The highest concentrations are characteristic in the O horizons (Mg – 4.8 and Ca – 1.5 mg/kg) for a significant part of the macroelements. The trace elements, Sr and Zr are distributed vary contrastingly (from 5.0 to 29.7 and from 5.6 to 47.1 mg/kg). Values of the R coefficient from 0.3 to 0.9 indicate the initial stage of post-pyrogenic restoration of soil properties, and the active accumulation of Mg, Ca, Ti, Fe, Sr, and other elements in the upper part of oxidized-gley permafrost gleyzem observed in the profile is a sign of active restoration. The soils contain about 3.4% iron, which more than 60–75% is the silicate group of compounds (Feс). The moisture content of soils and the prevailing reducing environmental conditions contribute to the formation of monotonous distributions in their profiles, and in soils without signs of stable hydromorphism, permafrost horizons contain almost 2 times more Feox and Feextr.

Abstract: Polycyclic aromatic hydrocarbons (PAHs) are the ubiquitous organic pollutants. They are formed as a result of incomplete oxidation of organic substance, for example, technogenic fuel combustion, heating system, wildfires, volcanism, and decomposition of organic residues. Special attention is given to pyrogenic factor of the formation of PAHs in soils. The subject of this research is PAHs in the soils of Batagaika thermoerosive carter in Northern Yakutia in Verkhoyansky Ulus in Yakutia. The author examines the peculiarities of two soil sections (indices B-VG-2019/1 and B-VG-2019/3). Both soils are post-pyrogenic and contain visible traces of a recent fire: embers are found in subsurface horizons of the examined sections, which indicate the recent fire. The following conclusion were formulated: 1) in soils, dicyclic PAHs account for 93%, while the proportions of tricyclic and tetracyclic compounds are roughly equivalent (4% and 3%, respectively); 2) the average values of individual PAHs in the upper (up to 30 cm) and lower (deeper than 30 cm) horizons differ. In the upper horizons, their total concentration is 27 ng/g, while in the lower horizons it is 14 ng/g; 3) in this case, the key biomarker of fires is naphthalene and its homologues. The absence of PAHs with considerable molecular weight most likely testifies to the relatively low fire intensity. The highest values of C/N ratio are noted in the bedding horizon: 10.89 and 3.31, and the lower soils are characterized with approximately 1, which is substantiated by the low content of carbon and nitrogen in the soil profile.