wk ee [Vou. 91 896). The in evolu- ng radiaysiderable of radio> place in t been inir detona1e subject ‘cial Subthe world ning and Sparrow 1964] “onmental ecological increased n, ‘ SOURCES. > exposed liation or ferred to lants and nd alpha ielear reariety of ited with rey elec1954) is sude to a ur above level the titude. um, and Oe a te ek EE hai eelPr abe e eae Bette Lette Ar \WARTIN : RADIOECOLOGY AND STUDY OF ENVIRONMENTAL RADIATION 285 their daughter products, Lowder and Solon (1956) have listed 17 other radionuclides which are known to occur in air, soil, or water. Carbon-14 and tritium (H-3) are produced in the upper atmosphere by nuclear reactions between cosmic rays and molecules of nitrogen and water. The air near the ground may also contain small quantities of gaseous deeay products which are derived from soil. According to one estimate Table 1. Estimated activity of naturally occurring radionuclides in an acre-foot of soil derived from igneous rock* Radio- Activity in nuclides K-40 Rb-87 C-14 & H-3 Radio- Activity in euries/acre-foot nuelides curies/acre-foot 33 x 10-3 6 x 1073 Ra-226 Th-232 1.5 x 10-3 1.9 « 10-3 ** U-238 3.0 x 10-3 *The formula for these calculations and those in Table 2 is: C=SAx AI x AE x grams/aere-foot C = Activity of radionuclide in euries per acre-foot SA = Specifie activity of radionuclides in curies per gram AI= Abundance of radionuclides (% x 10-2) in natural element ble infor- the fors and of terials in ee AE = Abundanee of element (% x 10-2) in environmental media Grams peracre foot = Soil: 15 x 108 Water: 1234 x 10° Sources of basie data: “SA”: Kinsman (1957) “AT”: Handbook of Physies and chemistry, 39th ed. “AE”: Lowder & Solon (1956) ** 0-14 in organic matter amounts to about lx 10-12 e/g carbon H-3 in soil water amounts to about 5x 10-16 e/g water Table 2. Hstimated activity of naturally occurring radionuclides in an acre-foot of sea water* Radio- Activity in nuclides K-40 Rb-87 C-14 & H-3 * ** Radio- Activity in curies/aere-foot nuclides curies/acre-foot 39 x 1078 32 x 10-10 *% Ra-226 Th-232 U-238 62 x 10-4 eR H4* See footnote following Table 1. C-14: ca. 1x 10-12 e/g of Carbon H-3 ca. 1x 10-16 e/g =ea, 1.2 10-3 e/aere-foot of Sea Water *** Not calculated. (Koval 1945) the gas which emanates from soils containing radium and other long-lived radio-elements has an average activity of ea. 2x 10° e/m? (e/m' = curies per cubic meter). Most of this is due to the presence of radioisotopes of radon (Rd-219,220,222) produced by the deeay of Ra-226. Hess (1943) has reported that the radon content of air near the ground is usually less than 1x10? ¢/m*, but one sample, collected during calm winter weather from a low area having no snow cover, contained 3 x 10° c/mof radon.