Uranium and thorium contents in soils and bottom sediments of lake Bolshoye Yarovoye, western Siberia.

The uranium and thorium contents in the soils and bottom sediments of the Lake Bolshoye Yarovoye natural system correspond to the data for the steppe climate zone and are noticeably lower than the background values for the Altai Territory as a whole. Factors that reduce the content of uranium and thorium are: 1 - lighter grain size distribution of the substrate, and, accordingly, the soils in this area; 2 - low content of organic matter (high ash content at 600 °C); 3 - the presence of significant quantities of quartz and calcite; 4 - general salinization of soils and the development of the solonchak process; 5 - remoteness from the region of material removal from the Altai mountains with its uranium-thorium-bearing granites and various mineraliszation. The distribution of uranium and thorium in the soils of the catchment area is heterogeneous. Minimum contents are observed in the soils of the boggy eastern coast and in its southern part in connection with the development of the solonchak process. This part of the catchment is characterized by high salinity (HCO3-- Na+) of water extracts in soils. Under subalkaline and alkaline conditions (pH 7.1-8.4) in soil waters, an increase in the content of these ions facilitates the transition of uranium to the liquid phase and its migration to the lake. In this part of the water area, the maximum uranium content in bottom sediments is observed. The results of cluster analysis indicate a change in the correlation of uranium and thorium during their redistribution from soils to bottom sediments. In soils, there is no correlation between uranium and thorium; in the bottom sediments, a strong positive correlation is observed between them (correlation coefficient 0.9). Uranium in soils has only a bond with Cr and possibly with Mn. The absence of a correlation with the elements of the mineral component of the soil confirms it finding, mainly in soluble form. In bottom sediments, both elements are associated with the mineral component. The established features of the distribution of uranium and thorium in the soils and bottom sediments of Lake Bolshoye Yarovoye indicate the need for detailed geochemical studies in lakes of a similar type. This will help to avoid ecological risks when choosing such lakes as anthropogenic objects.

Distribution of radionuclides in moss-lichen cover and needles on the same grounds of landscape-climatic zones of Siberia.

The radiation status of the landscape and climatic zones of Siberia at the turn of the 20th and 21st centuries is characterized using bioindicators/biomonitors: lichens, mosses, and needles, according to the results obtained at the sites of their joint growth. The maximal activity of 137Cs in these components is observed in the forest-tundra landscaped zone, polluted during the period of nuclear tests from the nuclear test site "Novaya Zemlya" and also due to slow migration of these elements to the soil under the arctic conditions. In the southern territories the specific activity of radiocesium in the moss-lichen cover and needles of conifers corresponds to the regional background, in the forest-tundra zone it sometimes exceeds it, but in general does not pose a threat to human health. Determined differences in the contents of radioactive elements in lichens and mosses that grow together on sites in different landscape zones of Siberia statistically not significant within one or two standard deviations, and recorded only in the range of 3Ï­ at the level of significance 0.05. Specificity of radionuclide distribution in lichens, mosses and needles (differences for epigeals and epiphytic lichens; different species selected at one site, annual and perennial needles, etc.) made it possible to identify the causes of variations in their activities in different zones, along with landscape features of these zones. In the needles of conifers potassium concentration exceeds the content in lichens, at lower levels of thorium and 137Cs. The contents of uranium and thorium in the studied components in all landscape-climatic zones correspond to the natural ones, except for the single local territories, because of the possible anthropogenic influence.

Fallout traces of the Fukushima NPP accident in southern West Siberia (Novosibirsk, Russia).

BACKGROUND: The fallout of artificially produced radioactive isotopes has been recorded at a site in southern West Siberia (54°50'43.6″ N, 083°06'22.4″ E, Novosibirsk, Russia). DISCUSSION: The highest activities of (131)I, (134)Cs, and (136)Cs were found in fresh snow precipitated on 02 April 2011, at 0.83, 0.092, and 0.002 Bq L(-1) of meltwater, respectively. The (131)I/(134)Cs ratio decreased from 9.0 on 02 April to 1.2 on 27 April, which is consistent with the radioactive decay of (131)I. This fallout can only have originated from the accidental emission of Fukushima Nuclear Power Plant, Japan, in March 2011.