1.School of Geography Sciences SWU;2.Southwest University
National Natural Science Foundation of China (No. 41877369) and the Natural Science Foundation of Chongqing (No. cstc2018jcyjAX0456
土壤颜色是土壤分类、气候重建和环境遥感的重要指标。铁氧化物和腐殖质是土壤的两大致色组分，主导了土壤的可见光波段的光谱响应特征。本文基于土壤中铁氧化物和腐殖质交叉致色效应不明确的问题，以高岭石（Kao）为基底，选取典型铁氧化物赤铁矿（Hm）和针铁矿（Gt）以及典型腐殖酸胡敏酸（Ha）和富里酸（Fa），基于高分辨率漫反射光谱方法（DRS），系统探讨了不同含量单一致色组分的光谱特征、颜色指数及其二元交叉干扰效应。研究发现，就单一组分的致色效应而言，红色Hm强于黄色Gt，黑色Ha强于棕色Fa；腐殖质加入对铁氧化物致色有明显影响，通常会使可见光波段平均反射率、明度（V）和彩度（C）降低，色调（H）偏黄，但Hm抗干扰能力大于Gt。Lab颜色系统的a*、b*以及DRS的红度（Red %）与黄度（Yellow %）对Hm和Gt含量变化敏感，可作为土壤铁氧化物定量反演的指标，但Ha的加入可导致Hm和Gt估值偏低，Fa对估值的影响较小，干扰形式与Hm和Gt的含量范围有关。基于此，本文给出不同腐殖酸含量条件下土壤Hm和Gt的估算公式，为理解土壤的颜色变化及铁氧化物定量提供重要参考，也为基于环境遥感的大面积铁氧化物调查奠定基础。
Soil color is an important index of soil classification, climate reconstruction and environmental remote sensing. Iron oxides and humus are the two major chromogenic components of soil, which dominate the spectral response characteristics of soil. 【Objective】This paper is based on the unclear cross-coloration effect of iron oxides and humus in soils and sediments.【Method】 We selected kaolinite as substrate, hematite (Hm) and goethite (Gt) as the representatives of iron oxides, humic acid (Ha) and fulvic acid (Fa) as the representatives of humus. The spectral characteristics, color changes and cross-interference characteristics of iron oxides and humus with different contents were discussed by high-resolution Diffuse Reflectance Spectrum (DRS). 【Result】It is found that in terms of the chromogenic effect of a single component, Hm is stronger than Gt, and Ha is stronger than Fa. The addition of humus has an obvious effect on the coloration of iron oxides, which usually reduces the Mean Reflectance, Value (V) and Chroma (C), and makes the Hue (H) yellowish. The anti-jamming ability of Hm is greater than that of Gt. The a* of Lab color system and the redness of DRS are sensitive to the change of Hm content. The b* of Lab color system and the yellowness of DRS are sensitive to the change of Gt content. They can be used as indices for the quantitative determination of soil iron oxides. However, the addition of Ha can lead to the underestimation of Hm and Gt, and the addition of Fa has less effect on the estimation depending on the contents of Hm and Gt. 【Conclusion】Based on this, the estimation formulas of Hm and Gt mixed with different contents of humic acids are given. It not only helps understand the color change of natural soils but also lays a foundation for iron oxide determination at a large scale based on remote sensing.
GUAN Yanxia, LU Jinmei, MA Rongjun, XING Dengchun, LONG Xiaoyong. Research on the Cross-Coloration Effect of Iron Oxides and Humus in Soil[J]. Acta Pedologica Sinica, DOI:10.11766/trxb202103200154,[In Press]