Soil Science and Soil Protection, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany.
Soil Science and Soil Protection, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany.
Sci Total Environ. 2021 Jun 15;773:145546. doi: 10.1016/j.scitotenv.2021.145546. Epub 2021 Feb 3.
Aeration of wetland soils containing iron (Fe) sulfides can cause strong acidification due to the generation of large amounts of sulfuric acid and formation of Fe oxyhydroxy sulfate phases such as jarosite. Remediation by re-establishment of anoxic conditions promotes jarosite transformation to Fe oxyhydroxides and/or Fe sulfides, but the driving conditions and mechanisms are largely unresolved. We investigated a sandy, jarosite-containing soil (initial pH = 3.0, Eh ~600 mV) in a laboratory incubation experiment under submerged conditions, either with or without wheat straw addition. Additionally, a model soil composed of synthesized jarosite mixed with quartz sand was used. Eh and pH values were monitored weekly. Solution concentrations of total dissolved organic carbon, Fe, S, and K as well as proportions of Fe and SO were analysed at the end of the experiment. Sequential Fe extraction, X-ray diffraction, and Mössbauer spectroscopy were used to characterize the mineral composition of the soils. Only when straw was added to natural and artificial sulfuric soils, the pH increased up to 6.5, and Eh decreased to approx. 0 mV. The release of Fe (mainly Fe), K, and S (mainly SO) into the soil solution indicated redox- and pH-induced dissolution of jarosite. Mineralogical analyses confirmed jarosite losses in both soils. While lepidocrocite formed in the natural sulfuric soil, goethite was formed in the artificial sulfuric soil. Both soils showed also increases in non-sulfidized, probably organically associated Fe/Fe, but no (re-)formation of Fe sulfides. Unlike Fe sulfides, the formed Fe oxyhydroxides are not prone to support re-acidification in the case of future aeration. Thus, inducing moderately reductive conditions by controlled supply of organic matter could be a promising way for remediation of soils and sediments acidified by oxidation of sulfuric materials.
湿地土壤中含有铁 (Fe) 硫化物，通气时会产生大量硫酸，并形成黄钾铁矾等 Fe 氢氧化物硫酸盐相，从而导致强烈酸化。通过重新建立缺氧条件进行修复会促进黄钾铁矾向 Fe 氢氧化物和/或 Fe 硫化物转化，但驱动条件和机制在很大程度上仍未得到解决。我们在实验室浸没条件下用或不用添加小麦秸秆的方式，对一种含黄钾铁矾的沙质土壤（初始 pH = 3.0，Eh ~600 mV）进行了一项培养实验，此外还使用了由合成黄钾铁矾与石英砂混合而成的模型土壤。每周监测 Eh 和 pH 值。实验结束时分析了总溶解有机碳、Fe、S 和 K 的溶液浓度以及 Fe 和 SO 的比例。采用连续 Fe 提取、X 射线衍射和穆斯堡尔光谱对土壤的矿物组成进行了表征。只有在天然和人工硫酸土壤中添加秸秆时，pH 值才会上升到 6.5，Eh 值才会下降到约 0 mV。Fe（主要是 Fe）、K 和 S（主要是 SO）向土壤溶液中的释放表明黄钾铁矾发生了氧化还原和 pH 诱导溶解。矿物学分析证实了两种土壤中黄钾铁矾的损失。在天然硫酸土壤中形成了纤铁矿，而在人工硫酸土壤中形成了针铁矿。两种土壤的非硫化、可能与有机物结合的 Fe/Fe 含量也有所增加，但没有（重新）形成 Fe 硫化物。与 Fe 硫化物不同，形成的 Fe 氢氧化物在未来通气时不易再次酸化。因此，通过控制有机物的供应来诱导适度的还原性条件可能是修复受硫酸材料氧化酸化的土壤和沉积物的一种很有前途的方法。
