Volume 51, Nº 8 (2018)

Four Scythian kurgans of the burial site Beloe Lake-3 were studied in the Turan–Uyuk Depression in the Republic of Tyva. They were constructed about 2565–2390 calendar years ago (calibrated with deviation 1 σ). Soil formation after 2500 yrs of the construction of the kurgans was examined in the interkurgan area. The properties of the background surface and ancient buried soils have much in common, and the difference between the soils of the four kurgans is small. This attests to the fact that the paleoclimatic conditions in the period of the necropolis construction remained stable and were similar to the modern climatic conditions. According to palynological data, the climate at the stage of the construction of the first two kurgans was a little more humid in comparison with the modern climate; it became somewhat drier after 95 years, during the construction of the third kurgan (2425 cal. BP) and again tended to humidification at the final stage of the necropolis creation. These changes in the paleoclimatic conditions are indicated by variations in the structure and composition of associations of xerophytes, mesophytes, hydrophytes, and ruderal plants. At the Uyuk stage, the area was mainly occupied by steppe phytocenoses with a predominance of xerophytes over mesophytes, and hydrophilous vegetation was allocated to moistened habitats near water reservoirs. Larch forests grew near water bodies. The variable anthropogenic impact on the landscape was stronger at the initial and final stages of the construction of the Uyuk culture necropolis.

Possibilities of NMR spectroscopy with ¹³C nuclei application to the study of soil organic matter and its various fractions is considered. This is a non-destructive method, which is particularly valuable in the analysis of various fractions of soil organic matter. It is regarded as a direct method, and, unlike most of indirect methods, it allows one to obtain reliable estimates of the ratio between virtually all groups of carbon atoms in different organic molecules, including those in humus specimens. Owing to impulse technique and high sensitivity, ¹³C-NMR spectra may be obtained immediately from soil samples without any extraction operations. The modern technique of obtaining spectra, their mathematical processing (Fourier transform), and data interpretation are considered. The results of applying ¹³C-NMR to the study of humus substances, water-soluble fractions of soil organic matter, and soil litters from different natural zones are discussed.

The study, generalization, and comparative analysis of data on the content and composition of polyarenes have been performed for the soils subjected to the impact of the following factors: (1) approach of bituminous material to the surface along the fault zone from the deep layers of sedimentary rocks with the formation of bituminous sandstones and asphalt lenses (Bakhilovo asphalt deposit, Zhiguli dislocations, Samara region); (2) periodical discharge of large amounts of volcanic tephra into the atmosphere resulting in the formation of pyroclastic deposits (near the Avacha Volcano, Kamchatka region); (3) increased geodynamic activity within the area of the recent blocky structure of the earth crust, where a spontaneous upward flux of fluids into the soil is possible (Istra morphostructural node, Moscow region); and (4) high fumarolic activity resulting in the impact of hot water and vapor on the surrounding soils (Golovnin caldera, Island Kunashir, Kuril region). It has been found that the considered manifestations of geological factors can be arranged into the following increasing order: (a) exposure of volcanic tephra as a parent rock (20 ng/g); (b) increased hydrodynamic and fumarolic activity (85–90 ng/g); and (c) penetration of asphalt into the sedimentary rocks (4800 hg/g). According to the diversity of polyarenes identified in the soils, the considered situations form the following increasing series: (a) 9 out of 11 identified polycyclic aromatic hydrocarbons (PAHs) are found in the area of increased geodynamic activity and in the region of volcanic tephra fallouts; (b) 10 PAHs are identified in the asphalt deposit; and (c) all 11 PAHs are identified in the area of fumarolic activity.

Isotopic composition of lead is a very sensitive indicator allowing us to determine even very low contamination of soils by this element, which is not noticeable from the change in its concentration against the background of the natural variability. Isotopic composition of loosely bound lead fractions (exchangeable and specifically sorbed) changes in soils of the Kologrivskii Forest State Natural Reserve under the impact of global or regional atmospheric transport and deposition of contaminants, though these soils are not subjected to the local technogenic pollution. The maximum portion of lead bound with the soil organic matter in the upper organic horizons reaches 75% of the total lead content. The portion of lead bound with iron and manganese (hydr)oxides increases down the soil profile. The portion of the residual fraction of lead also increases significantly down the soil profile. The most pronounced changes are observed for the ²⁰⁶Pb/²⁰⁷Pb ratio, which decreases from 1.20–1.24 to 1.15–1.18 under the impact of global pollution. The technogenic compounds of lead migrate down the soil profile. In the gray-humus gley alluvial soil (Fluvic Gleysol), low values of the ²⁰⁶Pb/²⁰⁷Pb ratio are observed for the exchangeable and specifically sorbed lead fractions in the entire soil profile, which is explained by the worse conditions for lead fixation in the profile of this soil in comparison with those in the podzolic soils.

The nuclear disaster at the Fukushima-1 nuclear power plant resulted in the widespread contamination of agrocenoses with radiocesium (¹³⁴Cs and ¹³⁷Cs) on the Honshu Island. Our study was performed on four agricultural fields located on gentle slopes of southern aspect 150 km to the northwest from the nuclear power plant. Three plots were tilled in different periods (in 2012–2013), and one plot remained untilled. The density of soil contamination and the specific activity of radiocesium in plants (June 2014) on tilled plots appeared to be permissible. Thus, the density of soil contamination varied within the range of 1.3–6.5 kBq/m², and the specific radioactivity of plants did not exceed 100 Bq/kg in plants. Such areas may be used as pastures without restrictions. At the same time, an increased density of the soil contamination (13–32 kBq/m²) and the concentration of radiocesium in plants (up to 138 Bq/kg) were detected in some areas not subjected to reclamation works. Such fallow lands are suitable as pastures only for feeding cattle for meat and for milk with their obligatory subsequent processing. On all the plots, the concentration of radiocesium in soils decreased down the soil profile. In general, radiocesium was accumulated on the middle and lower parts of slopes, which is associated with the development of water erosion and initial distribution of radiocesium during the snowmelt season. The air dose rate on the studied plots did not exceed the permissible safety level (0.2 μSv/h) and varied within the range 0.05–0.10 μSv/h. The maximum level of γ-radiation was determined on the fallow (untilled) plot. On tilled plots, γ-radiation was 30–50% lower. Therefore, soil moldboard plowin tillage to the depth of 20 cm with or without shallow cultivation is an efficient measure to reclaim agricultural lands with the initially low level of radiocesium contamination (up to 32 kBq/m²).

The state of irrigated soils of the Svetloyarsk irrigation system (Volgograd oblast) after 50 years or irrigation and ameliorative impacts has been assessed with the use of published and new field data, cadastral materials, and remote sensing materials. In the recent two decades, the area of regular irrigation and the volume of irrigation water have decreased, which has led to the lowering of the groundwater level to the depth of 5 m and more. The pattern of sown areas is characterized by a rise in the portion of winter cereals. Surface planing during the construction of the irrigation system led to a considerable transformation of the soil cover. On convex elements, solonetzic and other topsoil horizons were almost completely cut off. In many areas, they were replaced by a mixture of different horizons, including carbonaceous material. There are now significant areas of soils of different geneses with carbonates from the surface. Former solonchakous and slightly solonchakous soils are now at the stage of deep desalinization: soluble salts in them have been washed to the second meter, where slightly or moderately saline horizons with a predominance of sulfates have been formed. Irrigated areas on satellite images are specified by spotty patterns differing from those of natural solonetzic soil complexes because of the significant transformation of the soil cover during the construction and operation of irrigation system. The anthropogenically transformed soils can be mapped. Soil maps reflecting the modern state of the of soil cover of irrigated areas are given.

A total of 50 farmland soil samples were collected from the Yanqi County, Xinjiang, China, and the concentrations of eight heavy metal elements (As, Cd, Cr, Cu, Mn, Ni, Pb and Zn) were determined by standard methods. The spatial distribution, pollution level and ecological risk status of heavy metals were analyzed based on GIS technology, the Geo-accumulation Index (Igeo), the Pollution Load Index (PLI) and the Potential Ecological Risk Index (RI). Results indicated that: (1) The average contents of Cd, Cr, Ni, Pb, and Zn of farmland soils exceeded the background values of irrigation soils in Xinjiang by 1.5, 1.40, 1.33, 2.63, and 4.92 times, respectively. Cd showed a no-pollution level, Zn showed a partially moderate pollution level, Pb showed a slight pollution level, and Cr, Cu, As, Mn, and Ni showed no-pollution level, compared to the classification standard. The PLI values of heavy metal elements of farmland soils varied from 0.83 to 1.89, with an average value of 1.29, at the moderate pollution level. (2) The Individual Potential Ecological Risk Index for heavy metals in the study area was ranked in the order of: As > Ni > Cu > Cd > Pb > Cr> Zn. The RI values of heavy metals of farmland soils varied from 3.45 to 11.34, with an average value of 6.13, at the low ecological risk level. (3) Cu and Mn of farmland soils were mainly originated from the soil parent material and topography of the study area. As, Cd, Ni and Pb were mainly originated from human activities, and Cr and Zn may originated from both natural and anthropogenic factors in the study area.