摘要
讨论了在冲绳海槽伊平屋海岭和南奄西海丘两处海底热液喷出口附近海水中的铀系子体放射性核素2 10 Pb和2 10 Po浓度的垂直分布剖面 .在伊平屋海岭 ,甲烷及2 2 2 Rn的数据表明海底热液活动不强 ,总2 10 Pb和2 10 Po放射性均低于它们各自母体的放射性 ,2 10 Pb和2 10 Po在海水中的平均停留时间分别为 2 0和 2～ 5a ,而在以“黑色烟雾”为特征的海底热液活动强烈的南奄西海丘 ,在”烟雾”中的总2 10 Pb含量 ( 0 1 6 7× 1 0 -3～ 2 50× 1 0 -3Bq/kg)相对其母体2 2 6Ra贫乏 ,而总2 10 Po含量 ( 1 83× 1 0 -3～ 2 83×1 0 -3Bq/kg)则相对其母体2 10 Pb过剩 .该处海水中的2 10 Po的放射性高于东海陆架区及冲绳海槽其他海区 ,并且显示了2 10 Po过剩 .2 10 Pb/ 2 2 6Ra以及2 10 Po/ 2 10 Pb放射性比值的范围分别为 0 1～ 0 4和 1 1～ 7 8.在热液扩散带中2 10 Pb被优先从海水中清除 .控制南奄西海丘海水中2 10 Pb浓度的可能机制涉及到2 10 Pb通过扩散作用的横向输送 .在热液扩散带中高2 10 Po/ 2 10 Pb放射性比值表明2 10 Pb的耗尽及2 10 Po从海底热液喷出口的加入 .
Vertical profiles for the uranium-series radioisotopes 210Pb and 210Po were obtained at the two hydrothermal vent sites, the Iheya Ridge and the Minami-Ensei Knoll, in the Mid-Okinawa Trough in 1993 and 1994, respectively. At the Iheya Ridge, where the hydrothermal activity is not active as reflected by the CH 4 and 222Rn data, both the total 210Pb and 210Po activities show deficient relative to their parents, and the mean residence time of 210Pb and 210Po is about 20 and 2 ～ 5 a, respectively. At the Minami-Ensei Knoll, which is characterized by black smokers, the total 210Pb activity(0.167 × 10 -3 ～ 2.50 × 10 -3 Bq/kg) around the plumes is deficient relative to 226Ra but the total 210Po activity(1.83 × 10 -3 ～ 2.83× 10 -3 Bq/kg) is in excess relative to 210Pb. The 210Po activities are higher than those in the East China Sea and the Okinawa Trough, and excess 210Po has been found. The 210Pb/ 226Ra and 210Po/ 210Pb activity ratios are 0.1～0.4 and 1.1～7.8, respectively. 210Pb is preferentially scavenged in the hydrothermal plumes. The possible mechanisms governing the concentration of 210Pb in the Minami-Ensei Knoll involve a lateral transport of 210Pb via diffusion. The high 210Po/ 210Pb activity ratios in the hydrothermal plumes suggest a depletion of 210Pb and addition of 210Po in the hydrothermal vent area.
出处
《海洋学报》
CAS
CSCD
北大核心
2001年第6期59-75,共17页
