Estimating the absorption of soil-derived uranium in humans.

The aim of the present study was to improve the estimation of soil-derived uranium absorption in humans. For this purpose, an in vitro solubility assay was combined with a human study by using a specific edible soil low in uranium. The mean bioaccessibility of the soil-derived uranium, determined by the solubility assay in artificial gastrointestinal fluid, was found to be 7.7% with a standard deviation of 0.2%. The corresponding bioavailability of the soil-derived uranium in humans was assumed to be log-normal distributed with a geometric mean of 0.04% and a 95% confidence interval ranging from 0.0049% to 0.34%. Both results were used to calculate a factor, denoted as fA(sol), which describes the relation between the bioaccessibility and the bioavailability of soil-derived uranium. The geometric mean of fA(sol) was determined to be 0.53% with a 95% confidence interval ranging from 0.06% to 4.43%. Based on fA(sol), it is possible to estimate more realistic values on the bioavailability of uranium for highly uranium-contaminated soils in humans by just performing the applied solubility assay. The results of this study can be further used to obtain more reliable results on the internal dose assessment of ingested highly uranium-contaminated soils

Accuracy of Be-9-data and its influence on Be-10 cosmogenic nuclide data

A Be-9-solution has been chemically prepared from phenakite (Be2SiO4) mineral grains as commercial Be-9-solutions are too high in long-lived Be-10. The solution is intended to be used as a carrier for radiochemical separation of Be-10 to be measured by accelerator mass spectrometry (AMS). Thus, accurate data of the Be-9-concentration of this solution is essential to guarantee for high-accuracy Be-10 data in the future. After devastating preliminary results (similar to 8 % standard deviation), eight laboratories finally produced twelve individual results by four different analytical methods. A certain lab and method bias might be identified by sophisticated statistical evaluation. Some laboratories also (grossly) underestimate their uncertainties. Thus, the simple weighted mean of this round-robin exercise needed to be corrected by introducing additional allowances (Paule-Mandel-approach). The final result has been calculated to (2,246 +/- A 11) mu g Be-9/(g solution) with a reasonably low weighted standard deviation of 0.49 %. The maximum deviation of a single lab value from the weighted mean is 2.4 % when removing one Grubbs outlier (11 % off from the mean) from the data set. As Be-10-data, which is usually calculated from measured Be-10/Be-9 by AMS and stable Be-9, cannot be more accurate than the determined Be-9-concentration, it seems highly advisable to establish or improve quality assurance by having self-made carrier-solutions analysed at more than a single lab and regularly taking part in round-robin exercises

A record of ²⁴¹Am, ²³⁶U, ²³⁸U, ²³⁹Pu, ²⁴⁰Pu, ¹³⁴Cs and ¹³⁷Cs in surface seawater and ²⁴¹Am in aerosols shortly after the FDNPP incident occurred.

We obtained the rare data on low activity concentration of Am-241 in the surface seawater collected at about 210 km northeast of Fukushima Daiichi Nuclear Power Plant (FDNPP) on 29 April 2011. The concentration of U-236, U-238, Pu-239, Pu-240, Cs-134 and Cs-137 in that seawater was also determined and the atomic ratio U-236/U-238 and Pu-240/Pu-239 was calculated. The activity concentration of Cs-137 compared to that before the incident and the equal activity ratio of Cs-134/Cs-137 clearly indicate that the seawater was contaminated by the radioactive Cs discharged from the FDNPP, while the activity concentration of Am-241 as well as U-236, Pu-239 and Pu-240 was in the range of the values reported before the incident. Am-241 in the aerosols collected at about 120 km from the FDNPP, in which FDNPP derived U-236 and Pu isotopes were found, was analyzed. However, no significant larger amount compared to U-236 and Pu239+240 was found

Structure and collapse of a surface-grown strong polyelectrolyte brush on sapphire

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