不同潮时对厦门湾水体中234Th/238U不平衡的影响

厦门湾水体中2 3 4 Th 2 3 8U不平衡的时间序列数据表明 ,无论是溶解态、颗粒态2 3 4 Th还是总2 3 4 Th ,相对于母体2 3 8U均严重亏损 ,呈现出与开阔大洋水明显不同的特征。溶解态、颗粒态2 3 4 Th的停留时间介于 0 .5— 41d之间 ,其中低潮时停留时间比高潮时小 2— 4倍 ,证实近岸海域具有强烈的清除、迁出作用 ,且潮汐变化对海域颗粒动力学特征有重要影响。2 3 4 Th停留时间与总悬浮颗粒物浓度 (TSM)、Chl.a的关系则表明 ,近岸海域元素的清除、迁出作用主要受陆源颗粒物输送的影响 ,与生物活动关系并不密切。此外 ,非稳态与稳态清除模型结果的对比证明 ,稳态模型对于具有强烈清除、迁出作用的近岸海域是适用的

TIDAL EFFECT ON 234Th/238U DISEQUILIBRIA IN XIAMEN BAY CHEN Min,HUANG Yi-Pu,QIU Yu-Sheng

Temporal variations of 234 Th/ 238 U disequilibria in the water column were studied to reveal the particle dynamic characteristics in Xiamen Bay. The results showed that all of dissolved, particulate and total 234 Th have a large deficiency relative to 238 U throughout the water column in Xiamen Bay,which are distinctly different from those in open oceans. The residence times of dissolved and particulate 234 Th ranged from 0.5 to 41d. These short residence times confirmed that strong scavenging and removal processes exist in Xiamen Bay. The residence times of 234 Th in ebb are roughly 2\_4 times greater than those in flood tide,that is to say,tide phenomenon has a great effect on particle dynamics in studied sea area. The relationship among the residence times of 234 Th,TSM and Chl. a showed that scavenging and removal processes are mainly control by the continental particle contents transported by river,but not biological activities in situ. Based on the time series data of 234 Th and 238 U,we also use steady state scavenging model and non steady state model to calculate the residence times of 234 Th. The agreement between both models reveals that the steady state scavenging model is appropricate for the particle dynamics study in coastal ocean,in which the scavenging and removal of particle reactive elements are fast.