The migration of natural radionuclides in rocks, soils, plants of the Caucasus

The researches in high-altitude regions of 1800-3800 meters above sea level in the Eastern, Central, Western on the Great Caucasus have been carried out. The aim of this work is the study of the main factors influenced on the spread and migration of the natural radionuclides in the soils of the different regions of Caucasus and the exposure of the appropriate of its accumulation in plants. The content of 238U and 232Th in the surface layer (horizon A) in most cases is less than in the parent rocks. The biggest content of 238U and 232Th is in the volcanic rocks. It is noticed that from the Baku to the Krasnodar direction the content of thorium in the rocks is increased, but the content of uranium is decreased; and in the Central and East Caucasus the peak increase of the concentration of the both radionuclides is noticed.The highest concentration of uranium is observed in the mountain- meadow chernozemic soils of the Rocky Ridge and in the mountain- meadow chernozemic soddy soils of the Waterdivision and the Side Ridges. The maximum concentration of thorium is observed in the primitive soils of the Subarctic zone formed on the loose lays of the mountain rocks. It is naturally that on the accumulating of the radionuclides in the soils the soil-forming process has a definite role. But it shows, in particular, the relation 232Th/238U, which is the indicator of the process of the weathering and the direction of the soil-forming process. The greatest less of uranium relating thorium takes place in the immature primitive soils of the subarctic landscapes, that obviously occurs because of the differences of their leached regime. At the same time, the found value of 232Th/238U testifies the great mobility of uranium in comparison with thorium. It is found that the difference between the average concentration of uranium and thorium in the same plants collected in the different parts of the Great Caucasus can increase in 5 and more times. By means of comparison of 'the researched relations' it is determined that in some regions of the Great Caucasus the plants absorb thorium with the same intensity as uranium. In those regions where the prevalent forms of the nuclides are the mineraldeprival forms, the intensity of their intrusion into the biogenic cycle is high and they are more accessible for plants. In those regions where the radionuclides are mainly accumulated in the organic-mineral lays of the soils, the intensity of their joining the biogenic cycle is low and they are less accessible for plants. Saxifraga exarata, Saxifraga carinata, Festuca sulcata, Alchemilla caucasica, Rhododendron caucasicum, Juniperus sabina, Dryas caucasica can be used as bioindicators at radiating monitoring of natural ecosystems of the Great Caucasus, being the best concentrators of the radionuclides.