铁氧化物矿物是现代土壤和古土壤的重要组成, 其数量和形态是反映土壤成土条件和土壤风化发育程度的重要指标。 鉴于其粒度细小、 结晶度差、 含量低、 与粘土矿物密切共生, 加之基体效应的影响, 难以快速准确测定其含量; 鉴于某些测试方法自身的限制, 能用于铁氧化物矿物定量分析的方法也很少。 在分析目前常用测量方法的基础上, 选择漫反射光谱法(DRS)对云南元谋盆地所采古红土样品中的铁氧化物进行定量研究, 结果表明: 漫反射光谱法测得土壤样品在400~2 500 nm之间, 间隔2 nm共1 061个波段的光谱反射率最高45%左右, 各样品反射率特征较为一致; 漫反射光谱一阶导数显示, 光谱主峰位于575 nm处, 为赤铁矿的指示波谱段, 次级峰位于435 nm处, 为针铁矿的指示波谱段; 确定云南元谋古红土存在赤铁矿和针铁矿, 其含量范围3~5和5~10 g·kg-1, 此结果获得XRD方法分析方法的佐证。

Iron oxide is one of important minerals in modern soils and red paleosols, while the quantity and morphology of iron oxides are the critical indicators for soil-formation and weathering development. However, identification of iron oxides in soils and sediments is challenged by its small size, poor crystallinity, low content, close bond with clay minerals and the effect of soil matrix. Here the diffuse reflectance spectroscopy (DRS) method was adopted to quantify and semi-quantify iron oxides of red paleosols in Yuanmou Basin, southwest China. The spectral reflectance of paleosols was about 45%, measured over the range of 400～2 500 nm at an interval of 2 nm with a total of 1 061 bands. Nearly all samples exhibited the similar spectral reflectance, while the first and secondary derivative curve peaks occurred at 575 nm for hematite and 435 nm for goethite, respectively. Combination of CBD method and DRS technique the concentrations of hematite and goethitethe in red paleosols in Yuanmou Basin were 3~5 and 5~10 g·kg-1, respectively. The estimate on goethite and hematite using DRS was supported by the X-ray diffraction method.