Suchergebnisse

One of the important rare earth deposits is the Dong Pao localized in Lai Chau province, West-North of Vietnam. Generally, the deposit is composed of two parts, the lower and the upper. The lower part is composed of dolomite, limestone and intrusive rocks, while the upper part of the profile is represented by a weathered zone containing soil and fragments of mixed barite-fluorite ores. The concentrations of natural radionuclides, chemical compositions of ores, including rare earth elements (REE) in solid samples, were determined by gamma spectrometer equipped with a HPGe detector, laser ablation inductively coupled plasma mass spectrometry (LA ICPMS) and activation method, respectively. In the samples taken from the ore bodies within the weathered zone the REE concentration is about 10 wt.% and both 238U and 232Th amount to 0.01 wt.%, while in the samples from the hard part of ore the REE and 238U as well as 232Th contents amount only to 0.3 wt.% and 0.001 wt.%, respectively. So the enrichment of the REE and natural radioactive elements in the deposit is a consequence of the weathering processes. The water samples were taken from the streams, natural tap and thermal water intakes localized in the studied deposit and surrounding region. The 238U, 234U, 228Ra, 226Ra concentrations in the water samples were prepared by the adequate radiochemical procedures and measured using an alpha spectrometer coupled with silicon semiconductor detector and a/b liquid scintillation counter. In the stream water, the concentrations of both 226Ra and 228Ra vary from 100 to above 300 mBq/L, while in the natural tap and thermal waters they amount to tens mBq/L. The concentration of 238U, 234U in the thermal water is 80 and 110 mBq/L respectively, while in the surface water concentrations of uranium isotopes are below 30 mBq/L.References Bureau Veritas Canada, 2015. Certificate of analysis No KRA 15000229.1 Curtis N., 2011. 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AbstractThe measured gross alpha and gross beta activities in the edible muscle tissues of eleven selected marine species along the coast of North Vietnam varied from 10.2 ± 1.5 to 73.2 ± 8.1 Bq/kg (wwt) and from 10.6 ± 0.4 to 68.8 ± 2.8 Bq/kg (wwt), respectively. The lowest gross alpha activity was recorded for bigfin reef squid (Sepioteuthis lessoniana) as a result of its carnivorous diet, and the highest alpha activity was noted for blood cockle (Anadara granosa) as a result of its omnivorous diet. However, the gross beta activities in both carnivorous and omnivorous species were similar. The highest and lowest gross beta activities were observed for narrow-barred Spanish mackerel (Scomberomorus commerson) and for bigfin reef squid and squid (Teuthida), respectively. All three aforementioned species have carnivorous diets. The calculated annual committed effective dose resulting from the consumption of 25 kg of muscle tissue per year varied from 192 to 1375 μS with an average of 689 μS.