Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2000
Publication Date: 1/1/2001
Citation: Ventura, E., Nearing, M.A., Norton, L.D. 2001. Developing a magnetic tracer to study soil erosion. Catena. 43(2001):277-291. Interpretive Summary: In order to conserve soil from erosion it is helpful to know where soil erodes and how the sediment that is produced moves across the landscape. It sounds like a very simple matter, but measuring the movement of sediment across the landscape or even down a hillslope is not an easy task. It is difficult to know how far the material from a given portion of the land move s during a storm, or where it is deposited. Scientists have developed models to predict such movements, but they really have little data to verify the models. The purpose of this study was to develop a technique to measure the movement of sediment across landscapes. We use magnetized particles, which can be seeded in the upper layer of the soil. As erosion occurs, the magnetized particles are redistributed. A magnetometer is used then to map the magnetic content of the soil both in the area where the magnetic beads are placed and downslope. These results will benefit the environment and conserve our soil resources for growing food by reducing soil erosion.
Technical Abstract: Soil erosion is commonly measured as the quantity of sediment leaving a plot or watershed. Measurements of soil erosion patterns and sediment redistribution within plots or watersheds by direct monitoring are very limited. The objective of this study was to develop a direct and non- intrusive tracer method to study the sources, locations, patterns and rates of erosion and deposition of sediments. The magnetic tracer developed in this study consisted of polystyrene plastic beads embedded with a magnetic powder (magnetite). The "magnetized" beads, with a mean weight diameter of 3.2 mm and particle density of about 1.2 g cm-3, were uniformly mixed with soil and tested in the laboratory using simulated rainfall and inflow studies to simulate the interrill and rill components of soil erosion, respectively. In the interrill and rill experiments, the tracer was transported in the same proportion it was initially mixed with the soil. Given this fact, a magnetometer, which measures the soil's magnetic susceptibility, could be used to identify areas of deposition or detachment. The magnetic susceptibility would be enhanced or reduced depending on whether deposition or detachment occurs. To simulate detachment and deposition, a magnetometer was tested for different tracer concentrations and different thickness of soil containing the tracer. The magnetometer promises to be a sensitive, accurate, and useful tool to study the spatial variation of soil erosion when magnetic tracers are used.