Assessment of magnetite as a magnetic tracer for sediments in the study of ephemeral gully erosion: Conditioning factors of magnetic susceptibility. Issue 6 (15th April 2021)

• Record Type: Journal Article
• Authors: Zubieta, Elena; Larrasoaña, Juan C.; Aldaz, Alaitz; Casalí, Javier; Giménez, Rafael
• Is Part Of: Earth surface processes and landforms. Volume 46:Issue 6(2021)
• Page Start: 1103
• Page End: 1110
• Publication Date: 2021-04-15
• Subjects: concentrated‐flow erosion -- magnetic substances -- soil magnetism -- tracers; Geomorphology -- Periodicals; 551.4
• DOI: 10.1002/esp.5074
• Languages: English
• ISSNs: 0197-9337

Abstract

Abstract: In gully erosion, the detached soil can be transported over long distances along the landscape. The eroded material can be redistributed and/or deposited on the soil surface along the landscape and then eventually be buried by newly eroded and deposited sediment. There can be significant variability of the soil conditions (e.g., texture and moisture content) over which the eroded material travels. The eroded material can be detected through the use of magnetic tracers attached to or mixed with the eroded soil. In this study we evaluated the degree to which the magnetic signal of the magnetite is conditioned by (i) burial depth of tracer, (ii) condition of soil covering the tracer and (iii) tracer concentration. In the laboratory containers were filled with a specific soil. In the filling process, a 0.5‐cm layer of a soil–magnetite mixture was interspersed in the soil profile at a certain depth. Experiments encompassed three different soil–tracer concentrations (1000:1, 200:1, 100:1), four burial depths of tracer (0 cm, 3 cm, 5 cm and 10 cm from soil surface), and two different soils. In each case, the magnetic susceptibility was measured with a susceptometer. Experiments were repeated with different soil moisture contents. If the tracer is located under the soil surface, a minimum soil–tracer concentration of 200:1 is required for its correct detection. The intensity of the magnetic signal decreases dramatically with the vertical distance of the tracer from the soil surface. The maximum detection depth for the tracer's magnetic signal is strongly dependent on the natural magnetic susceptibility of the soil, which masks the tracer's signal. Variation in soil moisture content does not significantly affect the magnetic signal. For extensive field studies, the soil–tracer volume to be handled would be very high and therefore, it is necessary to explore new tracer application techniques. Abstract : In gully erosion, the detached soil can be transported over long distances along the landscape. This can be redistributed and/or deposited on the surface, and eventually buried by new eroded material. There can be significant variability of the soil conditions over which the eroded material travels. The presence of eroded material can be detected through the use of magnetic tracers. Variation of magnetic signal by tracer burial depth, soil conditions over tracer, and tracer concentration are evaluated.