岩成土的磁性测量及其与土壤发育的关系

Magnetic measurements on rock soils and its relation to soil development

应用环境磁学的方法测定了两种岩成土(红砂土和紫色土)的磁化率(χ)、频率磁化率(χfd)、非滞后剩磁(ARM)、等温剩磁(IRM )获得曲线、剩磁矫顽力(BCR)等磁性参数。结果表明两种岩成土的磁性主要受成土母岩的控制呈弱磁性特征,基本不存在超顺磁性颗粒,表现为不完整反铁磁性矿物的特征。热磁测定证明岩成土在高温下呈现明显的磁性增强现象并产生大量的超顺磁性颗粒,表现为亚铁磁性矿物的特征。岩成土的磁化率和频率磁化率与土壤的粘粒含量、游离氧化铁含量呈显著正相关关系,表现为土壤的磁性伴随成土作用程度的增大而增强, 具有十分重要的土壤发生学意义。

Magnetic susceptibility, frequency dependent susceptibility, anhysteretic remanent magnetization, acquisition curve of isothermal remanent magnetisation, saturation isothermal remanent magnetisation and demagnetisation parameters were measured on rock soils. It is found that the magnetic properties of rock soils were mainly controlled by soil forming parent rock, indicating that the rock soils have low magnetic values. Thermomagnetic analysis indicated that rock soils were characterized by magnetic enhancement and formation of superparamagnetic ferrimagnetic grain under high temperature. Statistical results indicated that magnetic susceptibility and frequency magnetic susceptibility of rock soils were significantly related to clay content and free iron content of soil. Results suggested that the continuous soil development resulted in enhancement of magnetic value (χ, SIRM etc.) and formation of superparamagnetic grains, indicating that magnetic values can be used indexes of soil development process.