USGS · 70015270
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R.S. Lively, E.P. Ney. 1987. Surface radioactivity resulting from the deposition of 222Rn daughter products. https://pubs.usgs.gov/publication/70015270
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The biotic exposure and uptake of radionuclides and potential health effects due to breccia pipe uranium mining in the Grand Canyon watershed are largely unknown. This paper describes the use of the RESRAD-BIOTA dose model to assess exposure of small rodents (n = 11) sampled at three uranium mine sites in different stages of ore production (active and postproduction). Rodent tissue and soil concentrations of naturally occurring uranium (234U, 235U, and 238U), thorium (228Th, 230Th, and 232Th), and radium (226Ra) radioisotopes were used in the dose model. The dose assessment results indicated that the potential internal, external, and total doses to rodents were below the US Department of Energy’s biota dose standard of 1 mGy d−1. As expected, tissue concentrations of 238U, 234U, and 230Th were in approximate equilibrium; however, 226Ra results in tissue were 1.25 to 5.75 times greater than 238U, 234U, and 230Th tissue results for 10 out of 11 samples. Soil at the three sites also displayed 226Ra enrichment, so it is likely that the 226Ra enrichment in the rodents was from soil via typical activities (i.e., burrowing, incidental ingestion, bathing, etc.) or by dietary uptake of translocated 226Ra. The results suggest that 226Ra is more mobile in this environment and bioaccumulates in these rodent species (e.g., in bones via the bloodstream). Internal dose accounting suggests that 226Ra is the radionuclide of most concern for rodent exposure and health.
Study of the sorption of 99mTc radiopharmaceutical compounds by soils has assessed the fate of these compounds in the event of a surface spill and examined the potential of these compounds as hydrologic tracers. Sorption from deionized water, filtered Missouri River water, and artificial seawater by five surface soils was investigated. For all water types, the Tc radiopharmaceutical compounds showed greater sorption than the uncomplexed pertechnetate. The most lipophilic complexes showed the highest sorption on soils.
Much attention in the radiological health community has recently focused on the management and regulation of naturally occurring radioactive materials. Although uranium-bearing minerals are present in a variety of fluorspar deposits, their potential consideration as naturally occurring radioactive materials has received only limited recognition. The uranium content of 28 samples of acid- and cryolite-grade (> 97% CaF2) fluorspar from the National Defense Stockpile was found to range from 120 to 24,200 μg kg−1, with a mean of 2,145 μg kg−1. As a point of comparison, the average concentration of uranium in the upper crust of the earth is about 2,500 μg kg−1. Leachability of this uranium was assessed by means of the Toxicity Characteristic Leaching Procedure (TCLP). The TCLP extractable fraction ranged from 1 to 98%, with a mean of 24% of the total uranium. The typically low concentrations of uranium seen in these materials probably reflects the removal of uranium-bearing mineral phases during the beneficiation of the crude fluorspar ore to achieve industrial specifications. Future NORM studies should examine crude fluorspar ores and flotation tailings.