Magnetic susceptibility of soil: an evaluation of conflicting theories using a national data set

Abstract

Magnetic susceptibility values for topsoils across England are combined with data for soil type, geochemistry and concentrations of magnetotactic bacteria in order to evaluate different theories for explaining soil magnetism. Strongly magnetic soils in unpolluted areas are found over weakly magnetic substrates and are dominated by ultrafine superparamagnetic grains. Magnetotactic bacteria are present in insufficient concentrations to account for strongly magnetic soils, and crop burning is discounted as a major factor. A small number of samples show high values associated with either airborne magnetic particulates from pollution or residual primary ferrimagnetic minerals from igneous substrates. The results are used to construct a new mechanism for the formation of secondary ferrimagnetic minerals that links abiological weathering and biological fermentation processes. The fundamental driving force in the mechanism is Fe supply, which may be linked to climate. Observed causative associations between climate and the magnetic susceptibility of loess-palaeosol sequences are supported by the findings.

Granulometric and magnetic properties of deposited particles in the Beijing subway and the implications for air quality management

“…Thompson and Oldfield, 1986). Numerous studies have demonstrated that magnetic techniques can be successfully used to monitor anthropogenic or geoanthropogenic pollution from surface soils (Dearing et al, 1996b;4 Jordanova et al, 2003;Qiao et al, 2011;Zheng and Zhang, 2008;Zhu et al, 2010), fossil fuel combustion (Heller et al, 1998), coastal areas (Dong et al, 2014;Zhang et al, 2009), urban dust (Bucko et al, 2011;Shilton et al, 2005;Shu et al, 2000;Xie et al, 1999;Zhu et al, 2010) and historical monuments (Schiavon and Zhou, 1996). Zhang et al (2012) show the first example for the use of magnetic measurements in detecting the iron-containing particles in the Shanghai subway system.…”

Magnetic susceptibility to identify landscape segments on a detailed scale in the region of Jaboticabal, São Paulo, Brazil

“…The mapping of magnetic susceptibility is ideal for studies that require large amounts of samples, as of spatial variability, for example (Dearing et al, 1996). Thus, the combined use of this method of indirect analysis with multivariate statistics provides valuable information for the mapping of homogeneous areas with a view to develop strategies for different agricultural systems.…”

Low‐temperature magnetic properties of lepidocrocite

“…[2] Magnetic methods have been applied in recent years to environmentally related problems, such as the monitoring of soils for contamination [e.g., Dearing et al, 1996], or as a proxy for climatic changes in terrestrial, lacustrine, and marine environments [e.g., Maher and Thompson, 1999;Thompson and Oldfield, 1986;Verosub and Roberts, 1995]. Because magnetic properties are sensitive to the presence of iron oxides in concentrations that are hardly detectable by spectroscopic and X-ray diffraction methods, they have been useful for the study of iron phases in soils [e.g., LeBorgne, 1955;Maher and Taylor, 1988;Mullins, 1977].…”