Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China; University of Chinese Academy of Sciences, Beijing 100049, China.
National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China.
J Environ Sci (China). 2023 Mar;125:470-479. doi: 10.1016/j.jes.2021.12.013. Epub 2021 Dec 27.
The flooding and drainage of paddy fields has great effects on the transformation of heavy metals, however, the transformation of Cr in basalt-derived paddy soil with high geological background values was less recognized. The typical basalt-derived paddy soil was incubated under alternating redox conditions. The Cr fractions and the dynamics of Fe/N/S/C were examined. The HCl-extractable Cr increased under anaerobic condition and then decreased during aerobic stage. The UV-vis spectra of the supernatant showed that amounts of colloids were released under anaerobic condition, and then re-aggregated during aerobic phase. The scanning transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) revealed that Fe oxides were reduced and became dispersed during anaerobic stage, whereas Fe(II) was oxidized and recrystallized under aerobic condition. Based on these results, a kinetic model was established to further distinguish the relationship between the transformation of Cr and Fe. During anaerobic phase, the reduction of Fe(III) oxides not only directly released the structurally bound Cr, but also enhanced the breakdown of soil aggregation and dissolution of organic matter causing indirect mobilization of Cr. During aerobic phase, the oxidation of Fe(II) and further recrystallization of newly formed Fe(III) oxides might induce the re-aggregation of soil colloids and further incorporation of Cr. In addition, the kinetic model of Cr and Fe transformation was further verified in the pot experiment. The model-based findings demonstrated that the Cr transformation in the basalt-derived paddy soil with high geological background values was highly driven by redox sensitive iron cycling.
稻田的淹水和排水对重金属的转化有很大的影响，然而，具有高地质背景值的玄武岩衍生稻田土壤中铬的转化却较少被认识。典型的玄武岩衍生稻田土壤在交替的氧化还原条件下进行培养。考察了 Cr 形态和 Fe/N/S/C 的动态变化。在厌氧条件下，HCl 可提取的 Cr 增加，然后在有氧阶段减少。上清液的 UV-vis 光谱表明，在厌氧条件下释放出大量胶体，然后在有氧阶段重新聚集。扫描透射电子显微镜（TEM）和 X 射线光电子能谱（XPS）表明，Fe 氧化物在厌氧阶段被还原并分散，而 Fe(II)在有氧条件下被氧化并重新结晶。基于这些结果，建立了一个动力学模型来进一步区分 Cr 和 Fe 转化之间的关系。在厌氧阶段，Fe(III)氧化物的还原不仅直接释放出结构结合的 Cr，而且还增强了土壤团聚体的分解和有机物的溶解，从而间接促进了 Cr 的迁移。在有氧阶段，Fe(II)的氧化和新形成的 Fe(III)氧化物的进一步结晶可能导致土壤胶体的再聚集，并进一步结合 Cr。此外，还在盆栽试验中进一步验证了 Cr 和 Fe 转化的动力学模型。基于模型的发现表明，高地质背景值的玄武岩衍生稻田土壤中 Cr 的转化主要受氧化还原敏感的铁循环驱动。
