Research data on the isotopic composition of carbon in soil lipids in the Zhirnovskoe and Bakhmet’evskoe oil and gas fields in the Medveditsa River basin, Volgograd oblast, Russia, are analyzed. Oil and atmospheric soil pollution is recorded. The variations in the isotopic composition are determined by both anthropogenic factors and the diversity of natural conditions. The isotopic composition of carbon in the lipids of the interfluvial soils (chernozems) is heavier (–26.9 to –29.2‰) than that in the alluvial soils (–29.4 to –31.3‰) because of the differences in the moistening and temperature conditions. Oil pollution appears as a lighter isotopic composition (–29.3 to –29.8‰) since oil isotopic composition is in general somewhat lighter (–28.4 to –30.6‰) as compared with unpolluted soils. Urban and transport infrastructure makes the isotopic composition of atmospheric CO2 lighter, thereby influencing the δ13С values of plants and soils.

— The polyarene complex of soils was investigated, and PAH sources were assessed quantitatively in soils in the area subjected to heterogeneous technogenic impact near the town of Zhirnovsk, Volgograd oblast. The objects of study were the soils on interfluve areas within the oil and gas field, including soils of agricultural lands, floodplains, urban area, as well as oil-contaminated soils. PAH concentrations vary from 16 to 330000 ng/g; light PAHs, naphthalene and phenanthrene homologues are predominant; heavy PAHs were detected in the amount of 78.5 ng/g mainly in the urban area. The Positive Matrix Factorization (PMF) model was used to indicate and quantify the PAH sources. The following sources of PAHs were identified: emanation, old oil injection, new oil injection, traffic, public gas-pyrogenic, public wood-pyrogenic, and biogeochemical. They determine, respectively, the following associations of PAHs in soils: diphenyl, anthracene-chrysene, chrysene-naphthalene, fluorene-benzo[ ghi ]perylene, tetraphene-benzo[ ghi ]perylene, pyrene-anthracene-benzo[a]pyrene, and phenanthrene associations.

The content of polycyclic aromatic hydrocarbons (PAHs) and carbon isotope composition in the peat of a palsa near Eletsky settlement, Vorkuta urban district, Komi Republic are analyzed. The carbon isotope composition of peat varies from –28.05 to –30.05‰ (average –29.15‰). The total PAH content varies from 11 to 360 ppb, with an average of 63 ppb and a median value of 34 ppb. Heavy compounds, such as benzo( a )anthracene and benzofluoranthenes, are prevalent among PAHs. The presence of PAHs in the peat is determined by three main factors: technogenic impact, wildfires, and biogeochemical soil processes. The prevalence of benzo( a )anthracene in the upper part of the palsa down to the bottom of the active layer suggests an anthropogenic impact (the influence of transport and domestic fuel combustion). The share of benzo( a )anthracene decreases with depth, while the share of benzofluoranthenes increases. Two sharp peaks of PAH content (260 and 360 ppb) are observed; they coincide with a local increase of carbon isotope values, most likely resulting from wildfires. The minimums in PAH content are presumably determined by the biogeochemical factor and the input of polyarenes generated by decomposition of plant residues. Carbon isotope composition of peat mainly reflects the isotope composition of vegetation, the degree of peat moistening, and the influence of pyrogenic factor.

The carbon isotope signatures and the content of polycyclic aromatic hydrocarbons (PAHs) in the pedogenic material of inclusions in ice wedges of the Batagay yedoma (Yakutia) are studied. The mean concentration of 11 PAHs is 170 ppb (minimum, 7 ppb and maximum, 430 ppb) and the mean δ 13 С value in soil lipids is –29‰ (minimum, –31.1‰ and maximum, –26.2‰). The prevalent polyarenes in associations are naphthalene homologs and phenanthrene. Trace amounts of heavy PAHs, including benzo[ a ]pyrene (an indicator of pyrogenic processes), are also detectable. The PAH contents and δ 13 С values in ice wedges show the trend of a decrease with depth. The δ 13 С values and PAH content suggest a pedogenic origin of the deposit: therefore, PAHs originate from plant residues and wildfires. The observed trend of changes in the concentrations of polyarenes along the ice wedge may be associated with the changes in landscapes in the Late Pleistocene.

We studied the ionic composition of ice, the content of suspended and dissolved trace- and major elements in ice, values of delta C-13, and the composition of PAHs of inclusions in the Late Pleistocene syngenetic ice wedges of the Batagay yedoma. For the first time, the complex geochemical study of Batagay megaslump was carried out. The ice of the upper and lower complex of different ages was studied. Mineralisation of the Late Pleistocene ice wedges of Batagay yedoma ranges from 66.56 to 424.8 mg L-1, from ultrafresh to desalinated, the ionic composition of the ice is bicarbonate-calcium and corresponds to snow formed under the influence of continental air masses. The proportion of Ca contained in dissolved form is not more than 20-30%; as for the other elements, the proportion of Mg, K, Na, Al, Fe, Mn, Sr, Ba in suspended form is greater than 90%. The content of trace elements in inclusions in ice wedges and soils is equal, which confirms the pedogenic origin of the inclusions in ice. According to our data, values of delta C-13 in lipids of the pedogenic material in ice decrease with depth. The lowest values (values of delta C-13 less than -30 parts per thousand) were observed in the ice wedge of the upper complex at a depth of 7.4-8.6 m. The increase of delta C-13 values of lipids from pedogenic material in ice wedges with depth is due to the landscape change from grassland ecosystems to forest ecosystems, and may also be influenced by the increased frequency of fires that occurred during the transition to forest ecosystems and the disappearance of large herbivores.

Soil hydrocarbons investigation is relevant nowadays, becuse of their ubiquitous distribution and toxity. In polluted areas it is important to find out the sources of hydrocarbons and their apportiontment. Many studies are devoted to this problem, which include many methods of statistical analysis. Studies were held on different territories in USA (Simcik, S.J. Eisenreich, P.J. Lioy, 1999; Li, Jang, Scheff, 2003), China (Zuo et al., 2007; Liu et al., 2009), Germany (Pietrogrande et al., 2011), etc. Current study was held for the part of Volgogradskaya oblast’ (Russia). Soils were analysed for 11 different PAHs content.

Profile distribution and seasonal dynamics of hydrocarbon gases (methane, ethylene, propane, nbutane and ethane) in soil air within the Istra morphostructure node and beyond the geodynamically active territory were analyzed. It was revealed that under probable inflow of hydrocarbons from the underlying geological strata the properties of hydrocarbon gaseous profile of the soils within the node are different from those of the background area. It is concluded that emanation and biogeochemical hydrocarbon status of soils could be indicated basing on their gaseous profiles.