Abstract Rare earth elements (REE) concentrations in acid mine drainage (AMD) are several orders of magnitude higher than those in other surface waters and could be a future supplementary source of highly valuable REE. Therefore, knowing the mobility constraints of REE in natural waters, particularly in AMD, is of interest. Precipitation of schwertmannite and basaluminite occurs due to mixing of REE-enriched AMD and neutral streams. The REE fractionation between AMD and solid phases has been investigated in several localities in the Odiel-Tinto (SW Spain) and Arroyo del Val (N Spain) basins. The mobility of REE is related to the precipitation of Fe and Al phases that occurs at different pH values. The behavior of REE during the mixing is conservative under low pH conditions (pH The strengths and limitations of a recently proposed thermodynamic model of REE sorption on basaluminite have been assessed by comparing the model predictions with observations of samples recovered in the field. The model is able to predict the REE distribution pattern and confirms the preferential sorption of heavy REEs (HREEs) and Y over light REEs (LREEs) in all the samples. However, the lack of synchronicity between basaluminite precipitation and REE sorption during mixing in an open flow setting precludes an accurate prediction of the REE concentration in the solid phase.

中文翻译：

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酸性排水中稀土元素的地球化学行为：建模成果与局限性

摘要 酸性矿山排水 (AMD) 中的稀土元素 (REE) 浓度比其他地表水中的浓度高几个数量级，可能成为未来高价值 REE 的补充来源。因此，了解 REE 在天然水域，特别是在 AMD 中的流动性限制是很有意义的。由于富含 REE 的 AMD 和中性流的混合，会发生施维特曼石和碱铝石的沉淀。已经在 Odiel-Tinto（西班牙西南部）和 Arroyo del Val（西班牙北部）盆地的几个地方研究了 AMD 和固相之间的 REE 分馏。REE 的迁移率与在不同 pH 值下发生的 Fe 和 Al 相的沉淀有关。该模型能够预测 REE 分布模式，并确认所有样品中重 REE (HREE) 和 Y 比轻 REE (LREE) 优先吸附。然而，在开放流环境中混合过程中，碱铝矿沉淀和稀土元素吸附之间缺乏同步性，因此无法准确预测固相中稀土元素的浓度。该模型能够预测 REE 分布模式，并确认所有样品中重 REE (HREE) 和 Y 比轻 REE (LREE) 优先吸附。然而，在开放流环境中混合过程中，碱铝矿沉淀和稀土元素吸附之间缺乏同步性，因此无法准确预测固相中稀土元素的浓度。