南极普里兹湾及其邻近海域表层水镭同位素的分布及应用

中国第27次南极科学考察期间(2010年12月30日至2011年1月16日),对普里兹湾及其邻近海域表层海水进行了226Ra和228Ra的分析,结果表明:226Ra和228Ra比活度的变化范围分别为1.47—2.43Bq/m3和0.17—0.45Bq/m3,平均值分别为2.13Bq/m3和0.29Bq/m3,228Ra/226Ra)A.R.(228Ra与226Ra的活度比)的变化范围为0.08—0.20,平均值为0.14。根据盐度和226Ra的质量平衡方程,计算出研究海域表层水中冰融水、南极夏季表层水和普里兹湾中深层水的份额。研究海域表层水中温度、盐度、226Ra、228Ra、228Ra/226Ra)A.R.和冰融水份额的空间分布显示,在埃默里冰架前沿海域,西侧海域较东侧海域具有低温、高盐、高226Ra、低228Ra、低228Ra/226Ra)A.R.、低冰融水份额的特征,证实埃默里冰架下水体东进西出的运动规律。根据埃默里冰架前沿东、西侧水体228Ra/226Ra)A.R.的差异,估算出埃默里冰架下表层水体东进西出所经历的时间为1.85a。此外,在普里兹湾湾口中部海域(66.5—67.5°S,72°—74°E),观察到次表层水的上升通风作用,该区域较高的228Ra含量和228Ra/226Ra)A.R.证明这些表层水体并非来自湾外绕极深层水的上涌,而可能来自湾内埃默里冰架输出水体。

SURFACE DISTRIBUTION OF RADIUM ISOTOPES IN THE PRYDZ BAY AND ITS ADJACENT SEA AREAS

226Ra and 228Ra in surface water in the Prydz Bay and its adjacent sea areas were measured during the 27th China Antarctic Research Expedition (from December 30, 2010 to January 16, 2011). Our results showed that 226Ra and 228Ra activity concentrations ranged from 1.47 to 2.43 Bq/m3 and from 0.17 to 0.45 Bq/m3, with an average of 2.13 Bq/m3 and 0.29 Bq/m3, respectively. 228Ra/226Ra)A.R. varied from 0.08 to 0.29, with an average of 0.14. Based on mass balance of salinity and 226Ra, fractions of three components, i.e. the ice-melted water, the Antarctic summer surface water and the Prydz Bay deep water, were calculated. Along the front of the Amery ice shelf, characteristics with low temperature, high salinity, high 226Ra, low 228Ra, low 228Ra/226Ra)A.R. and low fraction of the ice-melted water were observed in the western compared to the eastern region, indicating waters flow into the ice shelf at the eastern and exit from the west. The elapsed time for surface water transport from the eastern to the western was estimated as 1.97a according to the change of surface 228Ra/226Ra)A.R.. In addition, ventilation of sub-surface water was observed in the central mouth of the Prydz Bay (66.5~67.5°S, 72~74°E). Relatively high 228Ra and 228Ra/226Ra)A.R. in the central mouth of the Prydz Bay suggested that these surface waters came from the export waters from the western Amery ice shelf, and not from the upwelling of circumpolar deep water.