钦州湾河流沉积物中镭的解吸行为

罗浩; 李林蔚; 王锦龙; 钟强强; 杜金洲

doi:10.3969/j.issn.0253-4193.2019.04.003

钦州湾河流沉积物中镭的解吸行为

doi: 10.3969/j.issn.0253-4193.2019.04.003

华东师范大学河口海岸学国家重点实验室, 上海 200062

基金项目: 国家自然科学面上基金（41576083）。

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出版历程
- 收稿日期: 2018-02-13
- 修回日期: 2018-03-20

The desorption of radium isotopes in river sediments in Qinzhou Bay

State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China

摘要

摘要: 放射性镭同位素在海底地下水排放（SGD）等海洋物质变化过程的研究中具有优良的示踪作用，估算SGD通量时需要计算河流悬浮颗粒物的解吸通量。因此，对河流沉积物/悬浮颗粒物中镭同位素解吸行为的研究不可或缺，而目前对于粒度较小范围内镭同位素的解吸特征及其机理的研究依然不足。本文选用钦州湾河流沉积物，通过室内实验探究粒度和盐度对沉积物中镭同位素解吸行为的影响。结果表明，在沉积物平均粒径0.9~136.0 μm范围内，随着粒径增大，沉积物中镭同位素在海水（盐度为33.9）中解吸活度逐渐减小，且变化趋势也逐渐变缓，平均粒径大于43.7 μm后，解吸量几乎不变；在海水盐度4.9~33.9范围内，随着盐度增大，沉积物中镭同位素解吸活度逐渐增大，盐度大于24.9后，解吸量趋于不变。本文创新性地建立了沉积物表面分形结构的镭解吸理论模型，拟合得到钦州湾河流沉积物表面最大可交换态²²⁴Ra、²²⁶Ra和²²⁸Ra活度分别为1.13 dpm/g、0.17 dpm/g和0.85 dpm/g，以干重计；沉积物中²²⁴Ra、²²⁶Ra和²²⁸Ra最大解吸比分别为30%、7%和18%。钦州湾河流沉积物颗粒表面最大可交换态²²⁴Ra和²²⁶Ra活度分别处于全球中等水平和较低水平，而其最大解吸比分别处于全球较高水平和较低水平。本研究结果有助于更好地理解镭同位素的解吸行为，以帮助更准确地估算SGD通量。
- 钦州湾 /
- 镭同位素 /
- 河流沉积物 /
- 解吸行为
Abstract: Radium isotopes are one of the useful tracers to study the submarine groundwater discharge (SGD) processes. It is indispensable to estimate the desorption flux of the river sediment when estimate SGD flux. Thus, it is necessary to study the desorption behavior of the radium isotopes in river sediment/suspended particles, especially for the smaller size range of sediment. In the present work, the effects of grain sizes of sediments and salinities of sea water from the Qinzhou Bay on the desorption of radium isotopes were investigated by laboratory experiments. The results show that, within the grain size range of 0.9-136.0 μm, the desorption amounts of radium isotopes from the sediment to seawater (salinity 33.9) decrease with the grain size increase, and the desorption amounts keep almost constant when the grain size is larger than 43.7 μm. Within the salinity range of 4.9-33.9, the desorption amounts of radium isotopes from sediments gradually increase with the salinity increasing until the salinity reaches 24.9. By establishing creatively the radium desorption model using the sediment surface fractal structure theory, the maximum exchangeable activities of ²²⁴Ra, ²²⁶Ra and ²²⁸Ra from the river sediment of Qinzhou Bay are estimated to be 1.13 dpm/g, 0.17 dpm/g and 0.85 dpm/g, respectively; and the concerned maximum desorption ratios are 30%, 7% and 18%. Compared to those from other estuarine/coastal regions, the maximum exchangeable activities of ²²⁴Ra and ²²⁶Ra from the river sediments in Qinzhou Bay are in the middle or low ranges, while the maximum desorption ratios are in the higher or lower levels, respectively. The results of this study is expected to be useful to better understand the desorption behavior of radium isotopes and estimate accurately SGD flux.
- Qinzhou Bay /
- radium isotope /
- river sediment /
- the desorption behavior

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