北太平洋亚热带环流区表层水中^(226)Ra和^(228)Ra的分布与变化  

Surface distribution and temporal change of ^(226)Ra and ^(228)Ra in North Pacific subtropical gyre

作　　者：李艳平[1] 陈敏[1] 黄奕普[1] 蔡毅华[1] 

机构地区：[1]厦门大学海洋系,福建厦门361005

出　　处：《台湾海峡》2004年第3期261-267,共7页Journal of Oceanography In Taiwan Strait

基　　金：国家自然科学基金资助项目(40276025);中国大洋矿产资源研究开发协会国际海底区域研究开发计划资助项目(DY105 02 04和DY105 02 01)

摘　　要：对1999年9～10月采自北太平洋亚热带环流区的19份表层海水样品的Ra同位素分析表明,研究海域表层水中的226Ra、228Ra放射性比度分别介于0.67～0.92、0.08～0.30Bq/m3之间,平均值分别为0.74、0.11Bq/m3.228Ra/226Ra)A.R.活度比的变化范围为0.11～0.44,平均值为0.19.上述数值明显低于近岸海域水体的相应值,表现为典型的开阔大洋水的特征.从空间分布的特征看,研究海域Ra同位素含量与228Ra/226Ra)A.R.值均呈均匀分布态势.将本研究结果与历史数据进行对比后发现,本研究获得的226Ra、228Ra放射性比度比20世纪60～80年代得到的数据来得低,可能与水体层化作用加强导致的Ra补充量的减少以及生物生产力升高导致的Ra迁出量的增加有关.北太平洋亚热带环流区表层水中Ra同位素的时间变化与文献报道的该海域叶绿素a、硅酸盐、磷酸盐含量与初级生产力的历史变化趋势相吻合.Surface seawater samples were collected for Ra isotope measurements at 19 stations in the North Pacific subtropical gyre during September to October, 1999. The results showed that the specific activities of ^(226)Ra and ^(228)Ra in surface seawater ranged from 0.67 to 0.92 Bq/m^3 ((averaging) 0.74 Bq/m^3) and from 008 to 0.30 Bq/m^3 (averaging 0.11 Bq/m^3), respectively. In contrast with Ra contents in the coastal waters,the low Ra activity concentrations in the studied areawere consistent with those reported for the open ocean. Spatial distribution of ^(226)Ra, ^(228)Ra and ^(228)Ra/^(226)Ra)_(A.R.) showeda uniform characteristic in the studied sea areas. Compared with the historicaldata obtained in the North Pacific subtropical gyre, specific activities of ^(226)Ra and ^(228)Ra in the surface waterwere lower than those obtained in 1960～1990, indicating the effect of the global warming. At one side, the stratification of the upper ocean resulting from global warming decreasedthe Ra input from the deep ocean. On the other hand, the temporal increase of the biological production resulting from the change of climate-related ecosystemstructure further strengthed the Ra removal from the upper ocean. The temporal trends of Ra contents were consistent with those of chlorophyll a, silicate, phosphate and primary production previously reported for this sea areas.

关 键 词：镭同位素 核化学 ^226RA ^228Ra 表层水 半衰期 环流 

分 类 号：P715[天文地球—海洋科学] P734