多种核素在沉积物中的垂直和平面分布  

THE VERTICAL AND HORIZONTAL DISTRIBUTIONS OF SOME NUCLIDES IN SEDIMENT

作　　者：康兴伦[1] 顾德隆 张经[3] 朱校斌[1] 康建海[1] 秦晓光[3] 

机构地区：[1]中国科学院海洋研究所,青岛266071 [2]Department of Earth Sciences,University of Southern California [3]青岛海洋大学化学化工学院,青岛266003

出　　处：《海洋与湖沼》2002年第1期47-54,共8页Oceanologia Et Limnologia Sinica

基　　金：国家自然科学基金资助项目 ;4 95 76 2 99号

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 ,2 10 Pb和 2 3 4 Th在沉积物表层均不呈现过剩 ,2 3 8U系的各子体之间基本处于放射性平衡状态。本文中 2 14 Pb的最高比活度是(6 .2 0± 0 .2 1 ) 1 0 - 2 Bq/g,最低为 (3 .0 0± 0 .3 5 ) 1 0 - 2 Bq/g。2 2 8Ac的最高比活度是 (6 .6 0± 0 .5 8)× 1 0 - 2 Bq/g,最低为 (2 .80± 0 .3 8)× 1 0 - 2 Bq/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 ,2 2 8Th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 13 7Cs含量相当低 。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 210 Pb and 234 Th were not present in the surficial sediment,but members of 238 U series were in a rough radioactive equilibrium in the sediment. \;Radioactivity of 214 Pb varied from (3 00±0 35)×10 -2 Bq/g to (6 20±0 21)×10 -2 Bq/g;radioactivity of 228 Ac varied from (2 80±0 38)×10 -2 Bq/g to (5 46±0 31)×10 -2 Bq/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. 137 Cs 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 of 228 Th always exists in the surface sediment of the estuaries. This excess of 228 Th can be used for dating over time periods of the order of a decade.

关 键 词：Γ谱仪 核素 海洋沉积物 垂直分布 地球化学 铀238系 钍232系 平面分布 

分 类 号：P736.43[天文地球—海洋地质]