GEOCHEMISTRY AND GROUND PERMEABILITY AS DETERMINANTS OF INDOOR RADON CONCENTRATIONS IN SOUTHERNMOST SWEDEN

A study of the indoor radon gas levels was performed in 935 homes in Scania, southernmost Sweden, located on geologically different ground with regard to uranium (U) content. In one of these two areas the bedrock consists of alum shale with U contents exceeding 200 ppm. In the other area there is no U-rich bedrock. Indoor radon levels are influenced by U content and permeability as shown below. [GRAPHICS] The results show that the indoor radon levels were highest in homes located on bedrock with medium to high U content combined with a highly permeable drift covering the bedrock. The difference was statistically significant (P < 0.0001). Other results of the investigation are: 14 homes built from aerated concrete made from U-rich alum shale had higher levels than 767 homes with walls from other material (312 vs 106 Bq/m3; P = 0.0011); 242 homes with a cellar had lower radon levels than 563 without (62 vs 138 Bq/m3; P < 0.0001); further, 418 homes with private well had higher levels than 360 with public water supply (140 vs 82 Bq/m3; P < 0.0001). The results of the investigation show a profound effect of a combination of high bedrock U content and high cover permeability. The effect of the uraniferous drift on the indoor radon levels is evident. Thus, the geological conditions should be carefully considered when screening for high-risk buildings, as well as when planning for new ones. Also, the construction of the building and its water supply have some influence.