PubMed · 8767908
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C Mancini. [The radon problem].. https://pubmed.ncbi.nlm.nih.gov/8767908/
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An improved method is described utilizing extraction chromatography, anion exchange, and alpha spectroscopy for measurement of uranium isotopes in human and environmental surveillance studies. These methods provide a sensitivity of approximately 0.7 mBq per isotope per sample and are generally accurate within the precision of the measurements. The extraction chromatography methods greatly simplify separation of uranium from iron in silicate matrices and provide increased sample throughput and data quality for water, soil, and air filter samples. For bioassay samples, the coprecipitation/anion exchange/alpha spectrometric methods provide rapid throughput and sufficient sensitivity to meet new analytical performance standards in human monitoring studies. In addition, the 234U:238U data can be used as a fingerprint of natural vs. anthropogenic sources of uranium. For 1995 data from our laboratory, a large percentage (79-94% by matrix) of samples appear to be of natural 234U:238U isotopic composition. For all matrices, samples with higher uranium concentration generally have more depleted isotopic composition (smaller 234U:238U). A small percentage of soil (11%), air filter (3%), urine (3%), and water (3%) samples have depleted isotopic signatures at the 95% confidence interval, indicating anthropogenic contributions of uranium to these samples.
Following the 1986 Chernobyl event, large amounts of radioactive materials were deposited in nearby areas. Concentrations of various radionuclides were measured in air and surface soil. To study the resuspension of radioactive particulate, three different exposure situations were developed on the basis of the collected data under the auspices of the international BIOMOVS II (BIOspheric MOdel Validation Study) project. Modelers were asked to predict seasonal air concentrations and resuspension factors at several locations at different distances from Chernobyl for six successive years following the accident. Measurements of radionuclide deposition on topsoil were provided for each site along with information on soil, vegetation, land use, surface roughness, meteorology, and climate. In this paper, the three exposure situations are described, along with the initial data set provided to the modelers; two modeling approaches used to make the endpoint predictions are also presented. After the model predictions were submitted, the measured air concentrations and resuspension factors were released to the modelers. Generally, the predictions were well within an order of magnitude of the measured values. Time-dependent trends in predictions and measurements were in good agreement with one of the models, which (a) explicitly accounted for loss processes in soil and (b) used calibration to improve its predictive capabilities. Reasons for variations between predictions and measurements, suggestions for the improvement of models, and conclusions from the model validation study are presented.
Measured tritium oxide concentrations in air at various offsite locations are compared with concentrations predicted by three computer codes that are utilized at the Savannah River Site to estimate doses to maximally exposed offsite individuals. Annual average concentrations calculated by the computer models were compared with measured average concentrations taken from monitoring data collected over the last 10 y. The computer programs used for the comparison are AXAIRQ, MAXIGASP, and CAP88. The 10-y averaged ratios of predicted-to-measured tritium oxide air concentrations using AXAIRQ, MAXIGASP, and CAP88 are 1.89+/-0.56, 1.70+/-0.48, and 1.40+/-0.39, respectively. The difference in ratios is primarily due to different wind speed averages used within each of the models. These results show exceptional agreement, considering Gaussian plume models typically over predict annual average air concentrations by a factor of two to four.