Organic selenium (Se) accounts for up to 10–80% of total Se in soils, and l-selenomethionine (SeMet) is a typical organic Se species. However, the migration of SeMet in soils remains elusive. This study investigated the solid–liquid distribution, adsorption, desorption by phosphate, and self-oxidization of SeMet in solution under the influence of ferrihydrite, goethite, and hematite through batch experiments. Iron oxides could adsorb a much larger amount of SeMet than inorganic Se. At the initial Se element concentrations of 0–200 mg/L, the solid/liquid partition coefficient of SeMet was constant, which was 0.41, 0.43, and 0.50 on ferrihydrite, goethite, and hematite, respectively. In addition, the adsorption process of SeMet on the three iron oxides could be well described by the linear driving force model. Accordingly, the intraparticle diffusion coefficient of SeMet in ferrihydrite, goethite, and hematite was 1.4 × 10³, 7.9 × 10⁴, and 1.2 × 10⁵ nm²/min, respectively. The adsorption of SeMet on the three iron oxides was slightly influenced by the pH and the coexisting ions, such as Cl^–, NO₃^–, SO₄^2–, and H₂PO₄^–. The desorption ratio of SeMet on the three iron oxides by phosphate was lower than 2.5%. SeMet would aggregate the nanoparticles of iron oxides, resulting in a synergistic effect on the adsorption of phosphate. The oxidization ratio of SeMet was 23.9% in the solution, while it decreased to 17.1–17.5% in iron oxide suspensions. For this oxidization process, the three iron oxides exhibited varying effects to decelerate SeMet oxidation, as represented by the equivalent reaction. The findings of this study reveal the migration of SeMet in the water–soil interface under the influence of iron oxides, which can improve the understanding of Se cycling in the environment as well as provide some guidance for the better utilization of Se in soils and environmental remediation of Se pollution.

中文翻译：

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L-硒代蛋氨酸在以氧化铁为主的水土界面中的迁移

有机硒（Se）占土壤总硒的10%~80%，l-硒代蛋氨酸（SeMet）是典型的有机硒种类。然而，SeMet 在土壤中的迁移仍然难以捉摸。本研究通过批量实验研究了水铁矿、针铁矿和赤铁矿影响下SeMet在溶液中的固液分布、吸附、磷酸盐解吸和自氧化。与无机硒相比，氧化铁可以吸附更多量的硒蛋氨酸。在 Se 元素初始浓度为 0–200 mg/L 时，SeMet 的固/液分配系数恒定，在水铁矿、针铁矿和赤铁矿上分别为 0.41、0.43 和 0.50。此外，线性驱动力模型可以很好地描述SeMet在三种铁氧化物上的吸附过程。因此，SeMet在水铁矿、针铁矿和赤铁矿中的颗粒内扩散系数分别为1.4×10 ³、7.9×10 ⁴和1.2×10 ⁵ nm ² /min。 SeMet 在三种氧化铁上的吸附受 pH 值和共存离子（如 Cl ^-、NO ₃ ^-、SO ₄ ^2-和 H ₂ PO ₄ ^{- ）}的轻微影响。磷酸盐对SeMet对三种氧化铁的解吸率均低于2.5%。 SeMet 会聚集氧化铁纳米粒子，对磷酸盐的吸附产生协同效应。 SeMet 在溶液中的氧化率为 23.9%，而在氧化铁悬浮液中则降至 17.1-17.5%。对于该氧化过程，三种铁氧化物表现出不同的减缓 SeMet 氧化的效果，如等效反应所示。本研究结果揭示了铁氧化物影响下SeMet在水土界面的迁移情况，可提高对环境中Se循环的认识，并为Se在土壤和环境中的更好利用提供一定的指导。硒污染修复。