Abstract
Pedogenic magnetic fraction in soils is attributed to fine-grained particles, i.e. superparamagnetic grains. In the case of a strongly magnetic geogenic fraction, pedogenic magnetic contribution is hard to detect. To the best of our knowledge, detailed research into the masking of pedogenic superparamagnetic grains and quantification of this effect has not yet been carried out. The principal aim of our research is to quantify the influence of coarse-grained ferrimagnetic fraction on the detection of the superparamagnetic grains. In order to describe the masking phenomenon, volume and frequency-dependent magnetic susceptibility were determined on a set of laboratory prepared samples composed of natural substances: a diamagnetic quartz matrix, detrital coarse-grained ferrimagnetic crystals from alkaline and ultra-alkaline igneous rocks, and superparamagnetic soil concretions formed in the Haplic Cambisol. Mineralogy, concentration, type and grain size of the tested material were described by parameters of environmental magnetism. The magnetic parameters distinguish both geogenic multidomain and pedogenic superparamagnetic grains. The magnetic signal of the superparamagnetic grains is gradually masked by the increasing proportion of multidomain grains of magnetite/maghemite. The experiment clearly describes the masking effect and brings new insight to studies dealing with strongly magnetic soils of natural and/or highly contaminated origin as a tool for estimation of superparamagnetic pedogenic contribution.
Highlights
Magnetic signal of secondary over primary minerals may o ccur[22,23,24]
To the best of our knowledge, there has been no detailed research into the masking phenomenon of pedogenic superparamagnetic grains and quantification of this effect so far
The principal aim of this research was to show the influence of the coarse-grained ferrimagnetic fraction on the detection of the very fine superparamagnetic grains
Summary
Magnetic signal of secondary over primary minerals may o ccur[22,23,24]. The secondary magnetic minerals in the soil, including the secondary ferrimagnetic minerals (SFMs), can be pedo- and b iogenic[22], or anthropogenic in origin as technogenic magnetic particles ( TMPs25,26). The presented models of SP/stable SD magnetic e nhancement[11,32,33,34] cannot be applied to estimate the absolute amount of pedogenic magnetic fraction or to explain the mechanism of the masking phenomenon. The principal aim of this research was to show the influence of the coarse-grained ferrimagnetic fraction on the detection of the very fine superparamagnetic grains. For this purpose, the frequency-dependent magnetic susceptibility was used, i.e. the parameter which reflects the presence of the grains near the SP/stable SD boundary (~ 20 nm in diameter). To understand and describe the phenomenon of the ‘masking effect,’ research into its modelling was initiated
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