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基于漫反射光谱(DRS)的铁氧化物定量分析已用于北方黄土的研究,而在南方黄土中的适用性尚不清楚。本文选取江西九江黄土为研究对象,采用柠檬酸钠-重碳酸钠-连二亚硫酸钠(CBD)方法去除其中的游离铁,以此为基体分别加入不同比例的赤铁矿和针铁矿,通过多元线性回归方法建立了标样的铁氧化物含量与光谱反射率之间的校准方程。经检验,校准方程应用于未经CBD处理的剖面天然样品时,获得的赤铁矿含量较准,而针铁矿含量不准。原因可能在于:(1)混合体系中,赤铁矿与针铁矿互为基体,赤铁矿对针铁矿的干扰远大于针铁矿对赤铁矿的影响,这种差异在南方地区尤为明显;(2)CBD处理不能完全清除南方黄土中的针铁矿,可能与样品中含有部分结晶较好、粒度较粗的针铁矿有关,这也增加了针铁矿定量分析的不准确性;(3)铝的同晶替代现象对南方黄土影响更为显著,其中受晶格结构等影响,针铁矿的铝替代量比赤铁矿更大,可能对定量分析结果的准确性影响也更大。因而在南方黄土中,基于DRS的铁氧化物定量分析方法对于赤铁矿是适用和有效的,对于针铁矿的应用则需要慎重。
The quantitative analysis of iron oxides based on diffuse reflectance spectroscopy (DRS) has been used for the study of northern loess, but the applicability in the southern loess is unclear. In this paper, the loess in Jiujiang of Jiangxi Province was selected as the research object, and the free iron was removed by sodium citrate-sodium bicarbonate-sodium dithionite (CBD) method. Different hematite and goethite were added into the matrix, The linear regression method establishes a calibration equation between the iron oxide content of the standard sample and the spectral reflectance. After verification, the calibration equation is applied to the natural samples without profile of the CBD treatment, the obtained hematite content is relatively accurate, and the goethite content is not allowed. The possible reasons are as follows: (1) In the mixed system, the hematite and goethite each other as a matrix, the interference of hematite to goethite is much larger than that of goethite on hematite, especially in the south Obviously; (2) CBD treatment can not completely remove goethite in southern loess, which may be related to the fact that the sample contains partly crystallized goethite which has good crystallinity and coarse grain size, which also increases the inaccuracy of quantitative analysis of goethite ; (3) The phenomenon of isomorphous replacement of aluminum has a more significant effect on southern loess, in which the substitution amount of aluminum in goethite is larger than that of hematite due to the influence of lattice structure, etc., and the accuracy of quantitative analysis may also be affected Bigger Therefore, quantitative analysis of iron oxides based on DRS in the southern loess is applicable and effective for hematite, and caution is needed for the application of goethite.