摘要
天然放射性镭同位素在沉积物上的解吸行为是影响其在陆-海交换过程中的关键所在。采用沉积物室内解吸实验和现场采集间隙水测量224Ra含量两种方法,对水体盐度梯度控制镭在海南八门湾红树林沉积物的解吸行为进行了讨论。结果表明:沉积物上可交换态224Ra的最大量为0.44dpm/g,解吸比为35%。利用间隙水的224Ra含量确定镭的分配比Kd与水体盐度S呈反比例函数:Kd=8.4×102/S,与室内解吸实验的结果相比更能代表镭在沉积物上的真实解吸行为。在深度25—40cm内,湿地沉积物的224Ra处于与其母体228Th的平衡状态,但223Ra很可能处于相对其母体227Th亏损状态。
The desorption of four natural radium isotopes(224Ra, 223 Ra, 228 Ra, and 226Ra) from sediments affected their behavior in land-ocean interaction in coastal zones. According to indoor experiment and field observation on 224 Ra activities in pore water of sediments, we studied the effect of water salinity on radium desorption from bottom sediments in mangrove wetland, Bamen Bay, Hainan. The results show that the sediment contains 0.44 dpm/g of exchangeable 224 Ra, which corresponds to approximately 35% of the total 228 Th activity. The field observation data revealed an inversely proportional relationship between the distribution coefficient(Kd) and the water salinity(S): Kd = 8.4×102/S, which is more representative of the real behavior of radium desorption from sediments as compared with the results of the experiments. We deduced that the 224Ra-228 Th secular equilibrium was approached in the upper 25—40cm sediment column. In contrast, the deficit of 223 Ra relative to its parent 227 Th occurred possibly in the mangrove wetland.
出处
《海洋与湖沼》
CAS
CSCD
北大核心
2015年第1期65-76,共12页
Oceanologia Et Limnologia Sinica
基金
国家自然科学基金重点基金
40830850号
关键词
镭同位素
盐度
沉积物
分配比
红树林湿地
radium isotopes
salinity
sediments
distribution coefficient
mangrove wetland
