Polycyclic aromatic hydrocarbon (PAH) concentrations in soils and plants in the Bolshezemelskaya tundra have been investigated at the sites affected by coal mining in comparison with the control ecosystems. Contribution of individual plant species to the total PAH accumulation is based on plant biomass data. In shrub tundra communities, the highest PAH concentrations are found in Pleurozium schreberi moss due to its high biomass and ability for active PAH accumulation. This species can be used for ecological monitoring of PAHs concentrations in the tundra communities. Light PAHs are more abundant in soils, plants of both contaminated and control sites as well as in the coal. But the highest excesses of PAH content in comparison with the control values are found for the high-molecular-weight PAHs due to their minimal concentration at the control site. Research on PAH accumulation in the organs of plants has revealed that polyarenes had fallen on the shrubs surfaces from the atmosphere and get accumulated in the plant superficial tissues without further penetration. Deciduous plant species accumulate more PAHs in leaves than evergreen shrubs do. Plants of herbal life form accumulate PAHs mainly from soil.

Albic podzols under pine forests are more prone to fires on the planet. The influence of fire extends to all soil components, including chemical properties, microbiological characteristics, and the composition and structure of soil organic matter, which persists for a long time. Here, we present the results of a study of the morphological, physicochemical, and microbiological properties and features of soil organic matter (SOM) in the albic podzols of pine forests (Pinus sylvestris L.) not exposed to fires for a long time (from 45 to 131 years). The study areas are characterized by different numbers of old fires (from four to five) that occurred over the previous several centuries in various territories of the Russian Federation such as Central Siberia (CS) and the European North (EN). In general, the albic podzols developing in CS and EN are characterized by similar morphological and physicochemical properties, with high acidity and poor mineral horizons. In terms of the lower vegetation layer and stand parameters, forest communities at the CS sites have a lower density and species diversity than those in EN. The ground cover is almost completely restored 45 years after the surface fire. The upper mineral horizon of albic podzols in EN contains higher PAHs in comparison with similar horizons of the CS sites. In the soil of EN pine forests, the MB content in the mineral horizons is, on average, three times higher than those in CS. Differences were also found in the qualitative composition of the studied soils’ microbiomes. The EN soil communities are represented by a wide variety of bacteria and fungi. The presented soil parameters can be used as a reference in assessing the increasing impact of fires on pine forests and podzols.

The composition of polycyclic aromatic hydrocarbons (PAHs) in vegetation of natural hummocky peatlands in the forest-tundra subzone of the Komi Republic and its possible impact on the composition of polyarenes in peat were assessed. The content of polyarenes was estimated by the method of highly efficient liquid chromatography. The accumulation of polycyclic aromatic hydrocarbons was the highest in Polytrichum strictum, Betula pubescens, and shoots of Picea abies and smaller in Betula nana L., Salix lapponum L., and Carex limosa L. with the domination of low-molecular-weight PAHs. We did not reveal dibenz[a,h]anthracene and benzo[ghi]perylene in plants: they could be the products of soil-forming processes. It is shown that distribution patterns of PAHs in the permafrost-affected soils of peat mounds (Hemic Folic Cryic Histosols) and in the soils of open-water mire pools (Fibric Floatic Histosols) are similar. Small quantities of low-molecular-weight polyarenes were normally accumulated in the seasonally thawed layer. The content of heavy structures (mainly, benzo[ghi]perylene) strongly increased at the contact with permafrost and then slightly decreased in the underlying permafrost. The composition of PAHs in the active layer mainly depended on composition of polyarenes in plants. At the contact with permafrost, the active synthesis or release of high-molecular-weight compounds took place. The influence of the composition of PAHs in plants on their composition in peat greatly depended on the degree of peat decomposition. Reasoning from the natural model of peat formation in open-water mire pools, the composition of polyarenes in the upper peat horizons of such sites was affected by recombination of low-molecular-weight hydrocarbons in Sphagnum riparium and Eriophorum sp. In the course of long-term soil development, the decomposition of complex organic compounds in plant tissues (particularly, in Eriophorum sp.) results in the formation of heavy PAHs with a simultaneous increase in the content of low-molecular-weight polyarenes.

Fires play an important role in the modern dynamics of boreal ecosystems. The article presents the results of studying the effect of old fires on soils and soil organic matter (SOM) of native spruce forests that were last affected by fires in the previous 100 to 200 years. The studies were carried out in the European north-east of Russia (Komi Republic) and Central Siberia (Krasnoyarsk region). The objects of the study were typical Glossic Stagnic Retisol (Siltic, Cutanic). The time after the fire was determined by dendrochronological methods. Data on the content of water-soluble organic matter and densimetric fractions of soils were obtained; carbon and nitrogen stocks were calculated. The content of polycyclic aromatic hydrocarbons (PAHs) was established to characterize the effect of fires. Pyrogenic carbonaceous inclusions were morphologically diagnosed 200 years after the fire. In this regard, it is proposed to distinguish a “pyrogenic” subtype for soils with pronounced signs of pyrogenesis. Carbon stocks in soils of the Komi Republic varied from 5.7 to 15.7 kg C m⁻², and soils of the Krasnoyarsk region had an accumulation of 6.9–12.5 kg C m⁻². The contribution of the pyrogenic horizon Epyr to the total carbon and nitrogen stocks was 9–45%. It is suggested that pyrogenic carbon (PyC) can accumulate in light densimetric fractions (fPOM_<1.6 and oPOM_<1.6). The analysis of PAH content showed their high concentrations in the organic and upper mineral horizons of the studied soils (24 to 605 ng g⁻¹). The coefficient FLA (fluoranthene)/(FLA+PYR(pyrene)) was the most useful to diagnose the pyrogenic origin of PAHs in the studied Retisols.