RADON EMANATION IN SASKATCHEWAN SOILS

Saskatchewan prairie soils in central Canada were studied from areas where many homes are known to exceed the Health Canada indoor radon guideline of 200 Bq m(-3). This study sampled 32 soils from 11 sites, which varied in clay content and presence of bedrock materials. Soils were analyzed for U-238, Ra-226, Rn-222 in soil gas, bulk density, moisture, and particle size. Radon emanation from the soil samples varied from 10% to 43% and increased significantly with clay content with radon concentrations in soil gas of 18-38 kBq m(-3). Total uranium in soils was 2.1-4 ppm and 26-51 Bq kg(-1) dry weight for U-238, Th-234, and Ra-226. Homes built on soils with high clay content may be at greater risk of high radon levels, particularly when the soils are dry and cracked, enhancing their permeability to gases such as radon. One sample of coal bedrock, originating from Tertiary marine shales, was particularly high for total uranium (53 ppm), 238U, 234Th, and 226Ra activities (68-1,303 Bq kg(-1)) with radon emanation up to 1,363 kBq m(-3). Health Phys. 100(6): 565-573; 2011