Background and Aims

Many studies have considered whether all forms of rare earth elements (REEs) in the soil are potentially bioavailable. The general consensus is that the exchangeable and carbonate-bound mineral pool is bioavailable. However, within the rhizosphere, site-specific geochemical conditions and biological weathering (due to plants, animals and microbes) may cause insoluble pools of REEs in the soil to become plant bioavailable.

Methods

This study categorized soil into four fractions using the Community Bureau of Reference (BCR) sequential extraction method. The geochemical associations of REEs with soil fractions were assessed to determine which mineral and organic pools were most bioavailable by comparing the similarity of REE fractionation patterns in local plant tissues with the BCR extraction results for compatible soils.

Results

The results showed that the residual or more recalcitrant fraction of the soil displays a convex REE pattern with distinct depletion of middle REEs (MREEs) compared with light REEs (LREEs) and heavy REEs (HREEs). Some evidence suggested that Eu may be excluded by plants, as anomalous Eu concentrations were observed when the belowground plant tissue concentrations were normalized to the BCR extraction data.

Conclusions

This study demonstrates that the REEs in belowground plant tissue are closely related, not only to exchangeable and carbonate-bound phases, but also to reducible and oxidizable soil fractions. According to the REE patterns, MREEs are more mobile than LREEs and HREEs, indicating enhanced bioavailability of MREEs.

中文翻译：

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土壤池中稀土元素分布与植物吸收的关系：一项顺序提取研究

 背景和目标

许多研究都考虑了土壤中所有形式的稀土元素 （REE） 是否都具有潜在的生物利用度。普遍的共识是，可交换的碳酸盐结合矿池具有生物可利用性。然而，在根际，特定地点的地球化学条件和生物风化（由于植物、动物和微生物）可能导致土壤中不溶性 REE 库变得具有植物生物可利用度。

 方法

本研究使用社区参考局 （BCR） 顺序提取方法将土壤分为四个部分。通过比较当地植物组织中 REE 分馏模式的相似性与相容土壤的 BCR 提取结果，评估 REE 与土壤组分的地球化学关联，以确定哪些矿物和有机池的生物利用度最高。

 结果

结果表明，与轻 REE （LREEs） 和重 REE （HREEs） 相比，土壤的残留或较顽固的部分呈现凸起的 REE 模式，中间 REE （MREEs） 明显耗尽。一些证据表明 Eu 可能被植物排除在外，因为当地下植物组织浓度与 BCR 提取数据标准化时，观察到异常的 Eu 浓度。

 结论

这项研究表明，地下植物组织中的 REE 不仅与可交换和碳酸盐结合相密切相关，还与可还原和可氧化的土壤组分密切相关。根据 REE 模式，MREE 比 LREE 和 HREE 更具流动性，表明 MREE 的生物利用度更高。