Radon mapping in cluj-napoca city-a radon prone area from romani

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). Also in the east part of the city, where Someseni Spa is located,some cold springs with radon content up to 360 Bq/L (9.5 nCi/L) were emphasized. At present the citywater supply is assured by two sources: the old source consisting in a chain of wells delving nearriverbed of Somes (4 Km upstream Cluj-Napoca) and the new accumulation lake of Tarnita (20 Kmfrom Cluj-Napoca) which collects the surface waters arising from Apuseni Mountains.To see the radon potential of this region we measured in the last years the radon concentration ofindoor air in dwellings (detached houses and flats in blocks of flats) and the radon water content in thecity network water supply and also in some wells especially in two neighboring villages (Floresti andSomeseni) which are located on the Somes course. In addition we measured the radon exhalation andsoil radon content in this area. The integrated measurements of the indoor radon were made usingmakrofol track detectors for three months exposure and RADIM device was used for continuosmonitoring. The radon content in water was measured using the LUK-3A device (Jiri Plch SMM,Czech Republic) which was also used for radon soil measurement. The radon charcoal adsorptionmethod was used for radon flux exhalation and for radon soil content. The results for the indoor radonshow a difference between detached houses and flats, the mean value for winter season being highenough for the both situations 183 Bq/m3 and 70 Bq/m3 respectively. The radon content in water wasfollowed at five points in the network water supply and in several wells. The values range from 1 Bq/lto 32 Bq/L in the case of the network supply and from 12 Bq/L to 65 Bq/L in the case of the wells.The radon content in soil shows values in the interval of 15-55 kBq/m3 and the radon exhalationpresents an evident gradient perpendicular to the Somes riverbed. The variation of radon exhalationwas continuously measured for a month during April 1998. The average value of radon in soil for 49sites was 32.5 kBq/m3 and an average of 26.5 mBq/m2s was found in the case of the radonexhalation. These data confirm a slightly increased radon potential of this area.