IPMA-Instituto Português do Mar e da Atmosfera, Rua Dr. Alfredo Magalhães Ramalho, 6, 1495-006 Lisboa, Portugal; FCUL-Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal.
IPMA-Instituto Português do Mar e da Atmosfera, Rua Dr. Alfredo Magalhães Ramalho, 6, 1495-006 Lisboa, Portugal.
Sci Total Environ. 2021 Mar 10;759:144314. doi: 10.1016/j.scitotenv.2020.144314. Epub 2020 Dec 9.
Sediments colonised by three halophyte species, Spartina maritima (Curtis) Fernald, Halimione portulacoides (L.) Aellen and Sarcocornia fruticosa (L.) Scott) and bulk sediment from a SW European salt marsh (Tagus estuary, Portugal) were subjected to sequential extractions and analysed to assess the rare earth elements (REE) geochemical fractionation and to evaluate the plants' role in the mobility and bioavailability of these elements. The results showed that REE were mainly bound to the residual (yttrium and heavy-REE) and carbonate (middle-REE and heavy-REE) fractions, followed by the reducible and oxidisable (light-REE and middle-REE) fractions, while the easily soluble fraction was negligible. This fractionation evidenced a sediment REE mobility mainly dependent not only on carbonates but also on FeMn oxyhydroxides and on organic matter content. On the other hand, REE associated with the reducible and oxidisable fractions, and particularly the redox-sensitive Ce, may become more available, due to the redox condition seasonal changes that occur in salt marshes' sediments promoted by the plants' activity. Moreover, this study demonstrated that the REE bioavailability depends not only on the sediments' characteristics and the plants' seasonal activity but also on the specificity of each element, as demonstrated by the different fractionation patterns observed in the various sedimentary fractions.
三种盐生植物（米草、海蓬子和盐角草）和来自欧洲西南部河口盐沼（葡萄牙塔古斯河口）的块状沉积物经过连续提取和分析，以评估稀土元素（REE）的地球化学分馏，并评估植物在这些元素的迁移性和生物可利用性中的作用。结果表明，REE 主要与残渣（钇和重 REE）和碳酸盐（中 REE 和重 REE）组分结合，其次是可还原和可氧化（轻 REE 和中 REE）组分，而可溶解的组分则微不足道。这种分馏表明，沉积物 REE 的迁移性主要不仅取决于碳酸盐，还取决于 FeMn 氢氧化物和有机质含量。另一方面，与可还原和可氧化组分相关的 REE，特别是氧化还原敏感的 Ce，可能由于植物活动引起的盐沼沉积物季节性氧化还原条件变化而变得更易获得。此外，这项研究表明，REE 的生物可利用性不仅取决于沉积物的特性和植物的季节性活动，还取决于每个元素的特异性，这可以从不同沉积物组分中观察到的不同分馏模式得到证明。
