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The paper presents the results of indoor radon concentration survey in 201 homes and offices in Niska Banja (the Spa of Nis), a well-known health resort and a spa in the South-East of Serbia. Radon indoor concentrations were determined by active charcoal method, according to standard EPA procedure. The indoor radon concentrations were in the range of up to 200 Bq/m3 (47%), from 200–600 Bq/m3 (26%) and over 600 Bq/m3 (27%). Three areas of extremely high average radon concentrations were found (1340–4340 Bq/m3), with a maximum above 13,000 Bq/m3.The content of natural radionuclides (226Ra, 214Pb, 214Bi, 235U, 228Ac, 212Pb, 212Bi, 208Tl, 40K) and 137Cs, as well as the content of total uranium, thorium and potassium in mud used in peloidotherapy in the Health Institute “Niska Banja” was determined, too. The activities of the radionuclides were determined on an HPGe detector, by standard gamma spectroscopy. The results indicated considerably high amounts of total uranium and thorium (0.021 g/kg mud and 0.003 g/kg mud, respectively), due to the karsts origin of the soil. Keywords: Radon in air, Radionuclides, Soil, Spa, Gamma spectroscopy

Concentrations of 7 Be and 137 Cs in ground level air in the city area (Belgrade, central Serbia) were determined in the period from 1991–1996. The average monthly concentrations of 7 Be in ground level air were in the range of 2–7 mBq/m 3 with pronounced one or two maxima in summer or early fall and a minimum in winter. The average air concentrations for 137 Cs were from 0.5–8.5 × 10−5 Bq/m 3 , with a spread maximum in the spring-summer period and a pronounced maximum during the winter. A general increase in 7 Be and 137 Cs concentrations during 1993 was recorded. The maximum seasonal indices were 1.3 for 7 Be (summers) and 2.7 (late springs and early summers) and 3.4 (winters) for 137 Cs. No correlation with the amount of precipitation and 137 Cs concentrations in air was determined, while the washout effect of rainfalls seems to be more closely related with variations in 7 Be concentrations.

The effect of tropopause height on the content of Cs-137 and total beta activity in surface atmosphere was considered for the period of intensive nuclear weapon tests, from 1968-1971. The activity of Cs-137 in monthly air filter samples was measured by gamma spectrometry and total beta activity was determined by 2 pi proportional counters. The results were correlated with data on tropopause height. The results indicate that the movement of radioactive debris from the stratosphere into the troposphere occurs simultaneously with the changes in tropopause height. The content of long lived radionuclides in the troposphere follows the changes with a certain delay due to meteorological conditions in surface air and due to the location of sampling. (C) 1997 Elsevier Science Ltd.

The activity of natural radionuclides (226Ra, 238U, 235U, 232Th, and 40K) was measured in soils, meadow flowers, and honey from a mountain region in West Serbia. No statistically significant differences in the contents of natural radionuclides in soil or meadow flora from different soils (shale or limestone) were obtained, although concentrations were generally higher in shale soils than in soils mainly composed of limestone rocks. Activity of 226Ra, 238U, and 235U in plants was below minimal detectable concentrations (0.4 - 0.1 Bq/kg). The content of 232Th was higher in meadow flora from shale soils. For 40K, there were no significant differences in its concentrations in plants from different soils. The activity of natural radionuclides in honey did not depend on the type of soil or meadow flora, but the variations for 238U and 235U concentrations were high. Concentration factors for “soil-honey” phase were in the range 0.01-0.07, while for “soil-plant” and “plant-honey” phase they could be calculated only for 232Th and 40K and were in the range 0.1–3.0 and 0.09-0.02, respectively.