Comparison of retrospective and contemporary indoor radon measurements in a high-radon area of Serbia.

In Niska Banja, Serbia, which is a high-radon area, a comparison was made between two retrospective radon measuring methods and contemporary radon measurements. The two retrospective methods derive the radon concentrations that occurred in dwellings over longer periods in the past, based on the amount of trapped (210)Po on the surface of glass objects (surface traps, ST) or in the bulk of porous materials (volume traps, VT). Both surface implanted (210)Po in glass objects and contemporary radon in air were measured in 46 rooms, distributed in 32 houses of this radon spa-town, using a dual alpha track detector configuration (CR-39 and LR115) and CR-39 track etched detectors, respectively. In addition to the use of surface trap measurements, in 18 rooms (distributed in 15 houses) VT samples of suitable material were also collected, allowing to compare ST and VT retrospective radon concentration estimates. For each room, contemporary annual radon concentrations (CONT) were measured or estimated using seasonal correction factors. The distribution of the radon concentration in all data sets was found to be close to lognormal (Chi-square test>0.05). Geometric means (GM) are similar, ranging from 1040 to 1380 Bq m(-3), whereas geometric standard deviations (GSD) for both the retrospective methods are greater than for the CONT method, showing reasonable agreement between VT, ST and CONT measurements. A regression analysis, with respect to the lognormal distribution of each data set, shows that for VT-ST the correlation coefficient r is 0.85, for VT-CONT r is 0.82 and for ST-CONT r is 0.73. Comparison of retrospective and contemporary radon concentrations with regard to supposed long-term indoor radon changes further supports the principal agreement between the retrospective and conventional methods.

Radon survey in the high natural radiation region of Niska Banja, Serbia.

A radon survey has been carried out around the town of Niska Banja (Serbia) in a region partly located over travertine formations, showing an enhanced level of natural radioactivity. Outdoor and indoor radon concentrations were measured seasonally over the whole year, using CR-39 diffusion type radon detectors. Outdoor measurements were performed at 56 points distributed over both travertine and alluvium sediment formations. Indoor radon concentrations were measured in 102 living rooms and bedrooms of 65 family houses. In about 50% of all measurement sites, radon concentration was measured over each season separately, making it possible to estimate seasonal variations, which were then used to correct values measured over different periods, and to estimate annual values. The average annual indoor radon concentration was estimated at over 1500 Bq/m3 and at about 650 Bq/m3 in parts of Niska Banja located over travertine and alluvium sediment formations, respectively, with maximum values exceeding 6000 Bq/m3. The average value of outdoor annual radon concentration was 57 Bq/m3, with a maximum value of 168 Bq/m3. The high values of indoor and outdoor radon concentrations found at Niska Banja make this region a high natural background radiation area. Statistical analysis of our data confirms that the level of indoor radon concentration depends primarily on the underlying soil and building characteristics.

High natural radiation exposure in radon spa areas: a detailed field investigation in Niska Banja (Balkan region).

The measurement campaigns have been done in the rural community of Niska Banja, a spa town located in southern Serbia, to evaluate population exposure to natural radioactivity. After a screening survey in 200 houses, annual radon and thoron concentrations were measured in 34 houses, and in 2004 a detailed investigation was carried out at six houses with elevated indoor radon concentrations. The paper presents the results of these detailed measurements. The complementary techniques were applied to determine radon and thoron concentrations in indoor air, in soil gas, radon exhalation from soil, soil permeability, and indoor and outdoor gamma doses. Soil and water samples were collected and analysed in the laboratory. Indoor radon and thoron concentrations were found to be more than 1kBqm(-3) and 200Bqm(-3), respectively. Extremely high concentrations of soil-gas radon (>2000kBqm(-3)) and radon exhalation rates (1.5mBqm(-2)s(-1)) were observed. These results will be utilised to set up the methodology for a more systematic investigation.