Thermal enhancement of natural magnetism as a tool for tracing eroded soil


Alona Armstrong, School of Geographical and Earth Science, University of Glasgow, Glasgow, G12 8QQ, UK. E-mail:


Determining sources, quantities and travel distances of eroding soil is of increasing importance given its impact on- and off-site, the sediment-associated transport of nutrients, metals and micro-organisms and the ongoing need to provide data for soil erosion model development and validation. Many soil tracers have been developed; however, most comprise foreign materials, such as fluorescent beads and rare earth oxides, which cast doubts on the validity of tracing results given their different physical characteristics. To avoid these problems, we have investigated the potential of soil, which has been heated under reducing conditions to enhance its ferrimagnetic content, as a soil erosion tracer; while the technique has been used successfully to trace river sediment it has not been successfully applied to soil erosion studies. For a suite of 16 magnetic concentration-dependent properties, values were found to be significantly greater, by at least one order of magnitude, after heating, both for the bulk soil and nine individual particle size fractions. Individual size fractions could be differentiated using two different magnetic properties, thus illustrating the technique's potential to provide information on particle size-specific erosion. Soil box experiments demonstrated the potential for both in situ measurement of magnetic susceptibility and laboratory measurement of the magnetic properties of eroded sediment, to trace and quantify soil erosion. Thus, heated soil, with artificially-enhanced ferrimagnetic properties, is successfully demonstrated to have great potential as a size-specific, cost-effective and representative soil erosion tracer. Copyright © 2012 John Wiley & Sons, Ltd.