Johansen Mathew P, Prentice Emily, Cresswell Tom, Howell Nick
Australian Nuclear Science and Technology Organisation (ANSTO), Locked Bag 2001, Kirrawee DC, NSW, 2232, Australia.
Australian Nuclear Science and Technology Organisation (ANSTO), Locked Bag 2001, Kirrawee DC, NSW, 2232, Australia; University of Technology Sydney, 15 Broadway, Ultimo, NSW, 2007, Australia.
J Environ Radioact. 2018 Oct;190-191:130-133. doi: 10.1016/j.jenvrad.2018.05.001.
The adsorption of radiocesium and radiostrontium onto a range of natural materials has been well quantified, but not for the new media of environmental plastics, which may have enhanced adsorption due to surface-weathering and development of biofilms. Microplastic samples were deployed in freshwater, estuarine and marine conditions, then characterised using infrared spectroscopy to document changes to the plastic surface (vs interior). Synchrotron elemental mapping data revealed surfaces that were well-covered by accumulation of reactive water solutes and sulphur, but, in contrast, had highly discrete coverage of elements such as Fe and Ti, indicating adhered mineral/clay-associated agglomerates that may increase overall adsorption capacity. Plastics that had been deployed for nearly five months adsorbed radionuclides in both freshwater and estuarine conditions with the highest K for cesium (Cs) in freshwater (80 ml g) and lowest for strontium (Sr) in estuarine conditions (5 ml g). The degree of Cs and Sr adsorption onto plastics appears to be approximately 2-3 orders of magnitude lower than for sediment reference values. While lower than for sediments, adsorption occurred on all samples and may indicate a significant radionuclide reservoir, given that plastics are relatively buoyant and mobile in water regimes, and are increasing in global aquatic systems.
放射性铯和放射性锶在一系列天然材料上的吸附情况已得到充分量化，但对于环境塑料这种新型介质而言并非如此，环境塑料可能由于表面风化和生物膜形成而增强吸附作用。将微塑料样本置于淡水、河口和海洋环境中，然后使用红外光谱对其进行表征，以记录塑料表面（相对于内部）的变化。同步加速器元素映射数据显示，塑料表面被活性水溶质和硫的积累所覆盖，但相比之下，铁和钛等元素的覆盖则高度离散，这表明附着有与矿物/粘土相关的团聚体，可能会增加整体吸附能力。在淡水和河口环境中，已放置近五个月的塑料吸附了放射性核素，其中在淡水中铯（Cs）的分配系数最高（80 ml g），在河口环境中锶（Sr）的分配系数最低（5 ml g）。塑料对铯和锶的吸附程度似乎比沉积物参考值低约2 - 3个数量级。虽然低于沉积物，但所有样本都发生了吸附，考虑到塑料在水体中相对漂浮且易移动，并且在全球水生系统中不断增加，这可能表明存在一个重要的放射性核素储存库。
