| 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。 |
| 关键词: 镭同位素 盐度 沉积物 分配比 红树林湿地 |
| DOI：10.11693/hyhz20140100033 |
| 分类号: |
| 基金项目:国家自然科学基金重点基金, 40830850号。 |
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| EFFECT OF SALINITY ON RADIUM DESORPTION FROM SEDIMENTS IN MANGROVE WETLAND, HAINAN |
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GU He-Quan1,2, ZHAO Feng2, JI Tao1, WEN Ting-Yu1, ZHANG Jing1, DU Jin-Zhou1
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1.State Key Laboratory of Coastal and Estuary Research, East China Normal University, Shanghai 200062, China;2.South China Sea Environment Monitoring Center, SOA, Guangzhou 510300, China
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| Abstract: |
| The desorption of four natural radium isotopes (224Ra, 223Ra, 228Ra, and 226Ra) from sediments affected their behavior in land-ocean interaction in coastal zones. According to indoor experiment and field observation on 224Ra 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 224Ra, which corresponds to approximately 35% of the total 228Th 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-228Th secular equilibrium was approached in the upper 25—40cm sediment column. In contrast, the deficit of 223Ra relative to its parent 227Th occurred possibly in the mangrove wetland. |
| Key words: radium isotopes salinity sediments distribution coefficient mangrove wetland |
