2.13. Radioecological situation in the Spitamen district

Spitamen District is an administrative district within the Sughd Region of the Republic of Tajikistan. The district centre is the urban-type settlement of Navkat, located 28 km southwest of the city of Khujand. Spitamen district includes 1 urban-type settlement and 7 rural jamoats, where the physical characteristics of water were studied. In January-March 2017, radon monitoring was carried out on the territory of Spitamen district. The results of measurements of radon content and equivalent dose rate were summarised. The analysis of the results showed that the average values of volumetric activity of radon in the air of residential premises of Spitamen district are within the limits of error from 13 to 140 Bq/m³ (average value of 72 Bq/m³). Equivalent dose rate of background radiation for the measuring points is in the range from 0.07 to 0.24 µSv/hour. The values of radon concentration in the air of the residential premises of the villages of Kushtegirmon, Kurush, Langar, Metar and Andarsoy are in the range from 96 to 140 Bq/m³. These settlements are geographically located in the south-western part of the district territory. The mentioned area of the district is characterised by a mountainous zone, and the high radon concentration is related to the soil composition of this zone. The exception is the building of the village of Kushtegirmon, where the radon concentration is 96 Bq/m³. The increased radon concentration is probably related to the flushing materials of the mountainous zones. This exception requires further study and identification of the cause of the relatively high radon concentration. The air in buildings in the villages of Navkat (the centre of the district), Oktheppa, Saidkurgon, Mehnatobod, Khashtiyak, Tagoyak, T. Ulchaboev, Yangiobod has radon concentrations from 13 to 60 Bq/m³. These villages are located in the north-eastern part of the district. The low radon content is also connected with the composition of the soils of this zone. Analysis of the results showed that the average radon content in the air of residential premises of the Spitamen district is within the limits of error from 13 to 140 Bq/m³. The value of the equivalent dose rate for the measuring points is from 0.07 to 0.24 µSv/hour. A high concentration of radon in the air falls on the premises located in the territory of the mountainous zone in the south-western part of the district. This fact is a proof of radon infiltration into buildings through rocks. The arithmetic mean of Rn values for the studied buildings was 72.4 Bq/m³, and the total background radiation was 0.16 µSv/h, which is within the maximum permissible values for the 'population' category. From this it can be concluded that the radon content does not only depend on the building materials, but also on the terrain, the composition of the soil and rocks, and their permeability to radon. In this respect, the development of the area should take into account the geographical relief of the terrain, taking into account the studies carried out on radon indicators.