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臺灣應用輻射與同位素雜誌
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| 篇名 | 放射性活度比值應用於大屯火山區鈾／釭系列核種地質化學行為之研究 |
|---|---|
| 卷期 | 1:1 |
| 並列篇名 | Application of Radioactive Disequilibrium in Probing the Geochemical Behavior of Uranium/Thorium-Series Nuclides in Tatun Volcano Groups, and the Fate of Hokutolite |
| 作者 | 林群智 、 黃玉芬 、 耿念慈 、 劉威忠 |
| 頁次 | 069-080 |
| 關鍵字 | 鈾 、 釭 、 放射性不平衡 、 溫泉 、 大屯火山 、 北投石 、 uranium 、 thorium 、 radioactive disequilibrium 、 spring waters 、 Tatun volcanoes 、 Hokutolite |
| 出刊日期 | 200512 |
中文摘要
本研究針對大屯火山區溫泉中U/Th系列核種（包括：238U，234U，226Ra，233Th，228Th）進行分析，並分析採樣點環境之化學特性（如：酸鹼度、氧化還原電位及溫泉水中之Cl(上標 -)、SO4(上標 2-)濃度等），藉以探討放射性核種之遷移及其對放射性核種含量之變動的影響。研究結果顯示，溫泉水中U、Th之含量隨pH增加而遞減。234U/238U之放射活度比值(AR)可歸因於U(Ⅵ)之水解、α衰變核反跳及234U之選擇性瀝濾，然其不平衡現象並不明顯。而溫泉水中之230Th/234U，226Ra/230Th和232Th/232Th及底泥中233Th/234U，226Ra/230Th，228Ra/232Th，228Th/228Ra和228Th/232Th之放射活度比值均可見明顯之不平衡現象。溫泉水中之Cl和SO4(上標 2-)離子可促進U和Th溶入水中。溫泉水中之230Th/234U AR小於1，而底泥中之230Th/234U Ar (1.13-1.52)大於1，此可歸因於234U和230Th溶解度的迴異。溫泉水中326Ra/230Th的AR(0.60-34.8)隨Cl和SO4(上標 2-)濃度增加而下降，而底泥中226Ra/230Th的AR(1.57-21.5)則有相反之趨勢：此結果可歸因於230Th與Cl或SO4(上標 2-)的錯合及226Ra與(Ba，Pb)SO4的共沉澱反應。228Th/232Th在溫泉水中之AR(1.01-12.0)和底泥中之AR(1.02-25.6)均偏離1，且與228Ra和(Ba，Pb)SO4之共沉澱及228Th之錯合有關。
英文摘要
The activity concentrations of 238U, 234U, 230Th, 226Ra, 232Th, and 228Th in hot springs in the Tatun volcanic area were determined. Factors including acidity, redox potential, and C1- and SO42- concentrations in spring waters at the sampling sites have been investigated to allow interpretation of the migration of the radionuclides, and to elucidate the influence of these parameters on the variations of radionuclide contents. The contents of U and Th in water decrease with increasing pH. 234U/238U ARs were ascribed to alpha recoil and selective leaching of 234U, while the 234U/238U disequilibrium is not significant with regard to the statistical error. Radioactive disequilibria were found in 230Th/234U (0.04-0.63), 226Ra/230Th (0.60-34.8) and 228Th/232Th (1.01-12.0) in hot springs waters, and 230Th/234U (1.13-1.52), 226Ra/230Th (1.57-21.5), 228 Ra/232Th (1.10-277.4), 228Th/228Ra (0.09-1.23) and 228Th/232Th (1.02-25.6) in sediments. The contents of uranium and thorium decreased with increasing pH. The C1- and SO42- ions promote the dissolution of uranium and thorium. The 230Th/234U ratio increased, while the 226Ra/230Th ratio decreased with the Cl- or SO42- concentration, and was attributed to chemical difference between 230Th and 234U. 226Ra/230Th disequilibrium was attributed to the promotion of 230Th solubility by forming complexes with CI- or SO42- ions. All 228Th/232Th ratios deviated from unity due to the co-precipitation of 228Ra with barium and lead sulfate.