INFLUENCE OF GEOLOGICAL FACTORS ON URANIUM AND THORIUM DISTRIBUTION IN DRINKING WATER SALT DEPOSITS (REPUBLIC OF BASHKORTOSTAN)

Abstract

The relevance of the research is caused by the need to study the sources of natural radioactive elements entering drinking water and their areal distribution, as well as the possibility of using carbonate sediments of drinking water (scale) in geochemical and environmental studies. In the Republic of Bashkortostan (Russia), these studies are favoured by different geological structures within the area (mountainous area, foredeep and platform) and variety of rocks of different age and composition (volcanic, igneous, sedimentary, metamorphic), which determines the diversity of the microelement profile of the area. The aim of the research is to assess the radioactive elements content and spatial distribution in anthropogenic carbonate sediments (drinking water scale). Object of the research. The data on U and Thcontent in 467 samples of carbonate deposits(scale) from 267 settlements of the Republic of Bashkortostan was analysed. Samples were taken from various utensils (enamelled and electric kettles, pots, boilers), which is used for boiling water from centralized and individual (wells, streams) water sources. Methods. The method of instrumental neutron activation analysis based on the research nuclear reactor IRT-T TPU was used to analyse the uranium and thorium content. Data processing was carried out using software packages Statistica 8.0 and Microsoft Excel. The spatial distribution of natural radioactive elements was mapped using ArcGIS 10.2 in the Geostatistical Analyst module using the inverse distance method. Result. The data obtained allow speaking about uneven distribution of natural radioactive elements (U, Th) in anthropogenic carbonate deposits on the territory of the Republic of Bashkortostan. The average level of the studied chemical elements is characterized by low values of both uranium and thorium. Variations of their content in the studied formations are determined by the combined impact of natural and anthropogenic factors. The regularities of U distribution in scale samples correspond to the geological structure of the territory. Within the platform part, uranium distribution is more uniform than in the mountainous part of the Republic, which reflects the comparative homogeneity of geological and tectonic conditions. According to the results of mapping, four zones of high uranium content in samples of anthropogenic carbonate deposits were identified: Trans-Uralian, Uralian, Western and Southern.In Thspatial distribution there was no clear correlation with the features of the geological structure and metallogeny of the territory. There are three zones: Northern, Central and South-Eastern. Negative anomalies of Th content geographically coinciding with large mining centers are noted.Th/U ratio is characterized by a low value for the whole territory of Bashkortostan – 0,002. At the same time, positive anomalies of this indicator were recorded in the Northern and South-Eastern parts of the Republic, where they are mainly determined by geological component.

Keywords

• uranium
• thorium
• man made carbonates
• geoecology
• thorium-uranium ratio
• republic of bashkortostan
• southern urals
• geochemistry
• radioactive elements
• drinking water