厦门湾水体中234Th的垂直分布及其时间变异特征

１９９６年 ９～１０月在厦门湾上屿附近海域定点站连续６个航次测定了水柱中溶解态（ＤＴｈ）、颗粒态~(２３４)Ｔｈ（ＰＴｈ）和溶解态~２３８Ｕ，获得了~２３４Ｔｈ的时空分布图象。研究海域水柱中ＤＴｈ、ＰＴｈ和总~２３４Ｔｈ（ＴＴｈ）的放射性比度分别在０．８０～３．９５山／ｍ~３、１，９３～５．６５Ｂｑ／ ｍ~３和 ３．４７～９． １８Ｂｑ／ｍ~３之间，整个水柱中 ＤＴｈ、ＰＴｈ和ＴＴｈ均与~(２３８)Ｕ呈不平衡，其特征是~(２３４)Ｔｈ亏损，且亏损程度明显大于大洋水体。颗粒态~(２３４)Ｔｈ和总悬浮颗粒物（ＴＳＭ）在水体中的分布及其随时间的变化趋势相当一致，非生物过程可能对近岸海域水体中~(２３４)Ｔｈ的分布起着非常重要的作用。

Vertical distribution and temporal variation of 234Th in water column at Station “Shangyu”in Xiamen Bay

The vertical distribution and temporal variation of ~(234)Th activities in water column were studied at Station "Shangyu" in Xiamen Bay in six weeks. The specific activities of dissolved. particulate and total ~234Th are 0. 80~3. 95, 1. 93~5. 65, and 3. 47~9. 18 Bq/m~3, respectively. The vertical distribution of DTh activity is higher in surface and lower in bottom waters. and profile of PTh activity on the contrary. The both profiles ate closely related to the profile of TSM. PTh activities are higher than DTh in the coastal waters studied. Vertical distribution of total. dissolved, and particulate ~(234) Th relative to ~(238) U showed more deficiency throughout the water column in Xiamen Bay than in open ocean. Temporal variations of particulate and dissolved ~(234)Th correlated well with TSM and the distribution of ~(234)Th may be largely influenced by non-biological processes.