Micrometer-scale internal structure and element distribution of Fe-Mn nodules in Quaternary red earth of Eastern China
Micrometer-scale internal structure and element distribution of Fe-Mn nodules in Quaternary red earth of Eastern China
复制标题
中国东部第四纪红土铁锰结核微米级内部结构及元素分布
DOI：
10.1007/s11368-015-1212-5
复制
发表时间：
2016-11
影响因子：
3.6
通讯作者：
Lu, S.G.
中科院分区：
文献类型：
--
作者：
Yu, X.L.;Lu, S.G.
铁锰结核是热带和亚热带土壤的共同特征，含有丰富的成土过程、古环境变化和元素地球化学信息。本研究的主要目的是确定铁锰结核中元素的内部结构和空间分布，以更好地了解铁锰结核中重金属的三维内部结构、富集和动态，并为探索铁锰结核在土壤中可能的重金属固存和土壤环境意义提供更多的方面。材料与方法在中国Èastern第四纪红土上建立了典型的普林松样。将土壤b层Fe-Mn结核分为5-8、3-5、2-3和1-2 mm 4个粒径组。利用同步辐射x射线微计算机断层扫描（SR-mCT）观察了铁锰结核的三维微观结构，并利用配备能量色散x射线光谱仪（EDS）的扫描电子显微镜（SEM）研究了铁锰结核中的空间分布。通过选择性化学溶解、SEM/EDS和主成分分析等方法描述了结核中重金属与铁锰氧化物的关系。SR-mCT显示5-8、3-5和2-3 mm结节呈清晰的环形结构，而1-2 mm结节呈均匀结构。结核内部微观结构可分为富铁环、富锰环、铁锰重叠环和环间结构间隙四部分。Fe-Mn结核相对于土壤基质显著富集Mn、Pb、Ni、Cu和Zn。其中，结核中Mn和Pb的浓度分别是土壤基质中的150倍和90倍。在结核中观察到重金属在Mn和Fe氧化物相之间的明显划分，表明Pb主要存在于Fe氧化物中，而Ni、Cu和Zn主要存在于Mn氧化物相中。结论SR-mCT和SEM-EDS揭示了Fe-Mn结核的详细内部微观结构和土壤系统中重金属的地球化学动态。铁锰结核对土壤中铅、镍等有毒重金属具有很强的清除能力。结核中铁、锰的微观结构和空间分布反映了干湿交替的循环过程，是推断成土过程和土壤环境条件的重要依据。
PurposeFe-Mn nodules are the common feature of tropical and subtropical soils and contain abundant information of pedogenic processes, palaeoenvironmental changes, and element geochemistry. The main aim of the present study was to determine the internal structure and spatial distribution of elements in the Fe-Mn nodules to better understand the 3D internal structure, enrichment, and dynamics of heavy metals in nodules and to provide more aspects to explore the possible heavy metal sequestration and pedoenvironmental implications of Fe-Mn nodules in soils.Materials and methodsThe studied Typic Plinthudult was developed on Quaternary red earths in Èastern China. The Fe-Mn nodules in the Bs horizon of soil were separated and classified into four size fractions (5–8, 3–5, 2–3, and 1–2 mm). The 3D microstructure of Fe-Mn nodules was examined by means of synchrotron radiation-based X-ray microcomputed tomography (SR-mCT), and the spatial distribution of Fe and Mn in nodules was studied by scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS). The association of heavy metals with Fe and Mn oxides in nodules was described by selective chemical dissolution, SEM/EDS, and principal component analysis.Results and discussionThe SR-mCT images indicated that the 5–8, 3–5, and 2–3 mm nodules exhibited well-defined ring structures, while the 1–2 mm nodule exhibited homogeneous fabric. The internal microstructures of nodules could be divided into four parts: Fe-rich ring, Mn-rich ring, Fe and Mn overlapped ring, and the gap between ring structures. The Fe-Mn nodules were significantly enriched in Mn, Pb, Ni, Cu, and Zn relative to the soil matrix. In particular, the concentrations of Mn and Pb in the nodules were 150 and 90 times greater than those in the soil matrix, respectively. A clear partitioning of heavy metals between Mn and Fe oxide phases was observed in the nodules, indicating that Pb was mainly present in Fe oxides, while Ni, Cu, and Zn were mainly associated with Mn oxide phases.ConclusionsThe SR-mCT and SEM-EDS revealed the detailed internal microstructure of the Fe-Mn nodules and geochemical dynamics of heavy metals in the soil system. The Fe-Mn nodules have very high scavenging ability in sequestrating toxic heavy metals in soils, such as Pb and Ni. The microstructure and spatial distribution of Fe and Mn in nodules reflected the cycle of alternating drying and wetting conditions and served as an important basis for inferring the pedogenic processes and pedoenvironmental conditions.
登录
查看更多内容
影响因子：
2.9
作者：
D. Lindbo;F. Rhoton;W. Hudnall;N. Smeck;J. Bigham;D. Tyler
通讯作者：
D. Lindbo;F. Rhoton;W. Hudnall;N. Smeck;J. Bigham;D. Tyler
影响因子：
2.9
作者：
F. Rhoton;J. Bigham;D. Schulze
通讯作者：
F. Rhoton;J. Bigham;D. Schulze
影响因子：
5.8
作者：
A. Draut;P. Clift
通讯作者：
A. Draut;P. Clift
DOI：
10.2136/sssaj1996.03615995006000040042x
发表时间：
1996-07
影响因子：
2.9
作者：
G. White;J. Dixon
通讯作者：
G. White;J. Dixon
影响因子：
6.1
作者：
B. Dawson;J. Fergusson;A. Campbell;E. Cutler
通讯作者：
B. Dawson;J. Fergusson;A. Campbell;E. Cutler