长江中下游第四纪红土漫反射光谱特征及其环境意义

Diffuse Reflectance Spectrometry of Quaternary Red Clay in the Middle and Lower Reaches of the Yangtze River and Its Environmental Significance

赤铁矿(Gt)和针铁矿(Hm)是土壤和沉积物中比较常见的对气候变化具有指示作用的矿物。本文利用漫反射光谱技术(DRS)结合热磁对长江中下游地区的江西新余(XY)、湖南长沙(CS)、江西南昌(NC)、湖南岳阳(YY)、安徽郎溪(LX)地区较为典型的第四纪红土剖面的赤铁矿和针铁矿含量进行分析。结果表明:在第四纪红土中,无论是网纹红土、均质红土还是下蜀黄土,均含有一定量的赤铁矿和针铁矿,赤铁矿的一阶导数主峰的峰高值远大于针铁矿一阶导数主峰和次峰的峰高值,这表明第四纪红土中赤铁矿的含量远高于针铁矿,且在同一剖面中,均质红土中赤铁矿含量与网纹红土差别不大;结合热磁的数据及前人研究成果,推测均质红土层磁化率大于网纹红土层的主要原因可能是细颗粒磁性矿物含量的差异;均质红土与下蜀黄土层漫反射光谱特征存在一定的纬度地带性规律。

Hematite(Gt)and goethite(Hm)are relatively common minerals in soils and sediments that can indi-cate climate change.Combined with diffuse reflectance spectroscopy(DRS)data and sampleχ-T data,the content of hematite and goethite in the typical Quaternary Red Clay(QRC)profiles in the middle and lower reaches of the Yangtze River,such as Xinyu(XY)in Jiangxi province,Changsha(CS)in Hunan province,Nanchang(NC)in Jiangxi province,Yueyang(YY)in Hunan province and Langxi(LX),were analyzed.The results show that:in the QRC profiles,no matter reticulated vermicular red clay,homogeneous red clay or Xiashu loess,there are a certain amount of hematite and goethite.The main peak value of hematite on the DRS first derivative curve is much higher than that of goethite,which indicates that the content of hematite in the QRC is much larger than that of goe-thite.In the same section,the content of hematite in homogeneous red clay is not much different from that in ver-micular red clay.Combining theχ-T data and previous researches,it is speculated that the main reason for the high-er magnetic susceptibility of the homogeneous red clay than the vermicular red clay layer may be the difference in the content of fine-grained magnetic minerals.The DRS characteristics of the homogeneous red clay and Xiashu loess layers have certain latitudinal zonal laws.