| 摘要: |
| 应用γ谱仪测量了鸭绿江口及黄河口海域沉积物中的多种核素。由于这些区域,特别是黄河口,沉积速度快,泥沙从陆地直接搬运到海底,因此,210Pb和234Th在沉积物表层均不呈现过剩,238U系的各子体之间基本处于放射性平衡状态。本文中214Pb的最高比活度是(6.20±0.21)10-2Bq/g,最低为(3.00±0.35)10-2Bq/g。228Ac的最高比活度是(6.60±0.58)×10-2Bq/g,最低为(2.80±0.38)×10-2Bq/g。诸核素的平面分布与垂直分布均有一定波动,这种波动与沉积物的陆源变化及海洋水动力学作用有关。Ra与其他核素比较,更容易溶解,在地表水形成时,Ra已出现过剩。因此,在河口沉积物的表层,228Th呈现过剩。这种过剩可用来测河口的沉积速度。世界各主要有核国家已长期停止大气层核试验,因此,本文测得的137Cs含量相当低,有些层次已不能检出。
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| 关键词: γ谱仪,核素,238U系,232Th系 |
| DOI：10.11693/hyhz200201008008 |
| 分类号: |
| 基金项目:国家自然科学基金资助项目,49576299号 |
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| THE VERTICAL AND HORIZONTAL DISTRIBUTIONS OF SOME NUCLIDES IN SEDIMENT |
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KANG Xing-Lun1, KU Teh-Lung2, ZHANG Jing3, ZHU Xiao-Bin1, KANG Jian-Hai1, QIN Xiao-Guang3
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1.Institute of Oceanology,The Chinese Academy of Sciences;2.Department of Earth Sciences,University of Southern California;3.College of Chemistry and Chemical Engineering,Ocean University of Qingdao
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| Abstract: |
| Some nuclides in sediments from the estuaries of the Yellow River and the Yalujiang River were analyzed by γ-spectrometer. Because of a rapid accumulation of suspended sediment in the investigated regions,excess 210Pb and 234Th were not present in the surficial sediment,but members of 238U series were in a rough radioactive equilibrium in the sediment. Radioactivity of 214Pb varied from (3.00±0.35)×10-2Bq/g to (6.20±0.21)×10-2Bq/g;radioactivity of 228Ac varied from (2.80±0.38)×10-2Bq/g to (5.46±0.31)×10-2Bq/g. Horizontal distribution patterns of each nuclide from different regions and the vertical distribution with depth fluctuated, which resulted from the change of terrestrial origin of sediment and effect of hydrodynamics of the sea. 137Cs has a very low activity,often even not detectable,because the atmospheric nuclear test has been ceased for a long time by the nuclear powers. Ra is more soluble than the other nuclides and its excess in water arises when the surface water forms,therefore an excess of228Th always exists in the surface sediment of the estuaries. This excess of 228Th can be used for dating over time periods of the order of a decade.
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| Key words: γ-Spectrometer,Nuclide,238U series,232Th series |
