长江河口水下三角洲137Cs地球化学分布特征  

CHARACTERISTICS OF ^(137)Cs GEOCHEMICAL DISTRIBUTION IN THE SUBAQUEOUS DELTA OF THE CHANGJIANG ESTUARY

作　　者：张瑞[1] 潘少明[1] 汪亚平[1] 高建华[1] 

机构地区：[1]南京大学海岸与海岛开发教育部重点实验室

出　　处：《第四纪研究》2008年第4期629-639,共11页Quaternary Sciences

基　　金：国家重点基础研究发展规划项目(批准号:2002CB412401);国家自然科学基金项目(批准号:40106009)联合资助

摘　　要：文章通过对长江口水下三角洲采集的10个柱状样放射性核素137Cs的分析可以得知,长江口水下三角洲137Cs剖面中均存在清晰的最大蓄积峰,其峰值比活度介于5.68±1.03~21.74±1.39Bq/kg之间,平均值为14.11±1.10Bq/kg,最大蓄积峰所处的深度为55~117cm。剖面中137Cs最大蓄积峰应该与1963年的137Cs散落沉降相对应。长江口水下三角洲的表层沉积物中的137Cs比活度范围介于0~9.19±1.12Bq/kg之间,并且与长江流域其他地区的表层137Cs比活度相一致。长江口水下三角洲可探测到的137Cs比活度的最大深度范围在88~160cm的范围内变化,137Cs蓄积总量为2361.30±174.38~17714.94±262.14Bq/m2,平均值为9664.97±100.05Bq/m2,137Cs比活度的最大深度及137Cs蓄积总量均表现出从岸向海逐渐增加的趋势。实测的137Cs总量均大于长江流域的137Cs背景值,说明了长江口水下三角洲的137Cs蓄积既有大气散落直接沉降的来源,又有流域侵蚀带来的137Cs输入,并且主要以后者为主。通过放射性核素示踪模型分析长江口水下三角洲137Cs散落蓄积特征可以得知,长江口水下三角洲137Cs的蓄积以长江流域来源为主,说明了放射性核素137Cs在长江口水下三角洲沉积物中的蓄积主要受流域侵蚀因素的影响。A suite of sediment cores were collected in April 2006 from the subaquaous delta of the Changjiang（Yangtze River） Estuary,using gravity coring equipments. The length of the cores varies from 100cm to 160cm. Following visual inspection for geological parameters and photography of the cores,they were subsampled at 2cm intervals for the entire length of the core. In order to understand the characteristics of 137Cs geochemical distribution in the subaqueous delta of Changjiang Estuary, the sedimentary cores from this area were analyzed for 137Cs activities. 137Cs activities were measured by T-spectrometry based on photon energies at 661.62keV, and the weight of dry sediment was about 40g. The counting system is equipped with HPGe detector（ORTEC GEX30P-A）interfaced to a digital gamma-ray spectrometer. The detector was calibrated using the 137Cs standard sample supplied by Bedford Institute of Oceanography in Canada and IAEA-327. All the 137Cs profiles in this area show a maximum peak. The maximum 137Cs radioactivities are in the range from 5.68±1.03Bq/kg to 21.74 ± 1.39Bq/kg and the average maximum 137Cs radioactivities is 14.11 ＋ 1. 10Bq/kg. The highest peak corresponds to the maximum deposition in 1963. The depths of the maximum 137Cs radioactivities in the 137Cs profiles vary from 55cm to 117cm,The surface concentration of 137Cs covered the region from zero to 9. 19 ±1. 12Bq/kg,which is similar to the surface 137Cs radioactivity in other regions of the Changjiang Basin. Penetration depths of the 137Cs fluctuated from 88 ~ 160cm in this area,with over 100cm in most regions, and less than 100cm in parts of the region, and showed a tendency of increasing with distance from the coast. Furthermore, the inventories of 137Cs vary between 2361.30± 174.38Bq/m2 and 17714. 94±262. 14Bq/m2, with a mean value of 9664. 97± 100. 05Bq/m2, and show a crescent trend seaward. Moreover, compared with the 137Cs reference inventories of the Changjiang Basin, the data obtained by us in the delta are larger. This phenomeno

关 键 词：137Cs 137Cs总量长江口 水下三角洲 

分 类 号：P343.5[天文地球—水文科学] P736[天文地球—地球物理学]