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基于漫反射光谱和色度的土壤中赤铁矿和针铁矿半定量探讨
陈梓炫, 吕 镔, 郑兴芬, 刘 鑫
福建师范大学湿润亚热带山地生态国家重点实验室培育基地
摘要:
土壤中赤铁矿(α-Fe2O3)和 针铁矿(α-FeOOH)的含量和比例对气候变化具有明确的指示意义,对其半定量和定量是古气候研究的重要科学问题。通过选取黄土-古土壤样品以及红壤样品进行加热试验,对比加热前后的漫反射光谱(DRS)峰高,红光段,色度指标红度a*、黄度b*、b*/a* 参数,分析红壤与黄土中针铁矿和赤铁矿的组成和差异,探讨土壤中针铁矿和赤铁矿的半定量重建,结果表明:黄土样品的DRS一阶导数形态与红壤存在差异;红壤样品的a* 整体上高于黄土,b* 差异不明显,a* 与b* 具有协同变化的特点;红壤和黄土样品的DRS赤铁矿特征峰峰值与色度指标a* 密切相关。加热过程中针铁矿特征峰下降,并显示出黏土矿物峰和赤铁矿特征峰整体上升的特征,表明针铁矿脱水并生成赤铁矿。在有氧参与情况下,除针铁矿向赤铁矿转化外,细小颗粒的磁铁矿(Fe3O4)和不稳定磁赤铁矿(γ-Fe2O3)可能是有氧加热后产生赤铁矿的重要贡献者之一。
关键词:  漫反射光谱  色度  赤铁矿  针铁矿  黄土  红壤
DOI:10.13758/j.cnki.tr.2020.05.029
分类号:P575;P579
基金项目:国家自然科学基金项目(批准号:41877435和41402149)和福建师范大学创新团队项目(IRTL1705)
Semi-quantitative Study on Hematite and Goethite in Soils Based on Diffuse Reflectance Spectrum and Chroma
CHEN Zixuan, LÜ Bin, ZHENG Xingfen, LIU Xin
State Key Laboratory for Subtropical Mountain Ecology of the Funded by Ministry of Science and Technology and Fujian Province, Fujian Normal University
Abstract:
The contents and proportions of hematite (α-Fe2O3) and goethite (α-FeOOH) in soil have a clear indication for climate, so it is an important scientific issue in paleoclimate research to semi-quantitatively and quantitatively identifying their contents. Heating experiments were conducted on loess-paleosol and red soil samples, the composition and diversities of goethite and hematite were analyzed by comparing the parameters of Diffuse reflectance spectrum; (DRS) peak value, red light section and chroma indexes (a*, b*, b*/a*), and meanwhile semi-quantitative reconstruction of goethite and hematite were discussed. The results showed that the first derivative configuration of DRS in loess samples were different from those of red soil samples. Goethite sub-peak was obvious in loess samples while hematite characteristic peak was distinct in red soil samples. Generally, the values of a* in red soil samples were higher than those of loess samples, and the diversity of b* between loess and red soil samples was not obvious. Moreover, the changes of a* and b* were synchronous in soil. The value of hematite characteristic peak in red soil or loess samples was significantly correlated to a*. The characteristic peaks of goethite were decreased and clay mineral peaks were shown in heating process, meanwhile the characteristic peaks of hematite were increased, which indicate that goethite dehydrates and transforms to hematite. During the heating process with aerobic participation, fine grain magnetite (Fe3O4) and unstable maghemite (γ-Fe2O3) may be the important contributors to hematite formation except the conversion of goethite into hematite.
Key words:  Diffuse reflectance spectrum  Chroma  Hematite  Goethite  Loess  Red soil

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