The radon concentrations in indoor air and in soil air vary both on short term (daily, weekly) and onlong term (seasonal). The radon level and its changes depend on a few parameters, which may bedifferent from one building to another and from one type of soil to another. It is important to know theseasonal variation of the indoor radon levels if the level is to be compared with the national upperlimits in Europe for indoor radon concentrations.
Different aspects of the geogenic radon potential in a coal mining area in south-western Germany arediscussed. Due to the rather low specific radium activities of rocks and soils varying between 10 and70 Bq/kg a low geogenic radon potential can be expected. Radon concentrations in soil gas inabandoned mining areas are characterized by a lognormal distribution with a median value of 20kBq/m3. In the neighboring area with deep mining generally younger than two years, radon contentsincrease up to a median value of 38 kBq/m3.
Cluj Napoca City is the most important city from northwestern part of Romania, having about 350,000inhabitants. The Somes river, also the most important river of this country region crosses the city fromwest to east, but before it crosses a granite massive, named Maguri-Racatau, a region located at 35Km on the upper part of this water course. The first indicators of a possible radon prone area for Cluj-Napoca city and its neighboring was the water radon concentration from the old power supply of thecity with about 37 Bq/L (1nCi/L).
The effect of indoor gamma dose rate, permeability of soil, substructure, and ventilation habits of inhabitants were studied using data of 84 low rise residential houses collected in an area of enhanced indoor radon concentration. The radon concentrations varied from 30 to more than 5000 Bqm-3. Cross-tabulation, comparisons of means and multiplicative models were used to test the significance of the effects. In this study a quite high percentage of explained variation R2 - 68% - was found. It was found that the most important factors were the substructure and the permeability of the soil.
In 1995 and 1996 radon concentrations and effective air flows were measured in about 1500 Dutchdwellings built between 1985 and 1993. The goal of this investigation was to describe the trend inthe average radon concentration by supplementing the first survey on dwellings built up to 1984and to quantify the contributions of the most important sources of radon. In the living room of newdwellings the average radon concentration was 28 Bq m-3, which is 50% higher than in dwellingsbuilt before 1970.
For over ten years STUK (The Radiation and Nuclear Safety Authority, Finland) has performedsystematic indoor radon mapping with municipal health authorities. In the most radon-proneprovinces (Uusimaa, Kymi and Hme) there are about 480,000 low-rise dwellings. It is expectedthat in 51,000 homes the action level of 400 Bq/m3 is exceeded, of which about 6,000 have beendetected. In the rest of Finland the numbers are: 820,000 low-rise dwellings, 17,000 expectedcases of exceeding the limit, of which 800 were detected, respectively.
The use of two mapping methods, kriging and moving average, in mapping the indoor radon risk, isinvestigated. Both methods are applied to three databases: simulated radon data, data collected inSouthern Belgium with low sampling density, and data collected in Luxembourg. We use commercialsoftware (SURFERR 6) for kriging, as well as softwares developed by the authors, especially for the radoncase, for kriging and for moving average. Simulated data prove to be very useful in this context. Weconclude that kriging as implemented in SURFERR 6 may not be well adapted to radon mapping.
All buildings, depending on their design and particularly on how they are vented, are polluted to some extent with radon. Radon and its daughters may be trapped within buildings and accumulate there, thus threatening the health of their dwellers. Radon is an inert radioactive gas whose emanation into the building can mostly come from the underlying soil and from the building materials. The unhealthy buildings risk starts to act with tendency of saving energy and the related limitation of room ventilation to minimum.
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