A PRELIMINARY STUDY USING U-238 AND TH-232 RADIOACTIVE PARENT AND DAUGHTER ISOTOPES TO DETERMINE RADON CONTENT IN SOME SOILS AND ROCKS IN THE SPRINGFIELD, MISSOURI AREA

Soil and related bedrock shale and limestone samples, as well as a common type of lawn fertilizer were collected. All samples were treated and analyzed under the same physical conditions. Each was dried, disaggregated or crushed in a porcelain mortar and pestle, sieved and the <63 mesh portion saved for analyses. A 600 gram portion of each sample was counted for 20 hours in a 4020 Canberra Gamma Spectrum Analyzer. The number of atoms for each U-238 available isotope and the same for Th-232 in each sample was compared, including use of regression analyses. Isotopes of U-238 were used to determine Rn-222 content because of interference of other gamma isotopes with that of radon. Commonly used Charcoal Kits and Digital Radon-222 analyzers were not able to give reliable radon analyses.

Results indicated U-238 isotope concentrations were highly correlative in all soil samples. The same was true of Th-232 isotopes and in split portions of the fertilizer. Concentrations of all U-238 isotopes were much higher in fertilizers than in all other samples. Springfield lawn soils were higher in Rn-222 related isotopes than in bedrock indicating possible additions of fertilizer. The same was not true of soils collected in the country areas. Concentrations of U-238 and Th-232 isotopes in a soil profile indicated an active eluviation - illuviation mechanism. This appears to indicate concentrations of radon in the “B” soil horizon where foundations of many homes are constructed. Content of U-238 isotopes varied inversely with those of Th-232 in all sample types.

More area samples need to be analyzed for verification of results. Similar data obtained from bedrock and related soil samples in the Branson, and Kansas City areas would be interesting to integrate into this study.