Developing a magnetic tracer to study soil erosion

Soil erosion is commonly measured as the quantity of sediment leaving a plo t or watershed. The techniques for measuring soil erosion patterns and sedi ment redistribution within plots or watersheds by direct monitoring are ver y limited. The objective of this study was to develop a direct and non-intr usive tracer method to study the sources, patterns and rates of erosion and deposition of sediments in erosion plots. 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 wit h soil and tested in the laboratory using simulated rainfall and inflow stu dies to simulate the interrill and rill components of soil erosion, respect ively. 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 b e used to identify areas of deposition or detachment. The magnetic suscepti bility would be increased or reduced depending on whether deposition or det achment occurs. To simulate detachment and deposition, a magnetometer was t ested for different tracer concentrations and different thickness of soil c ontaining the tracer. The magnetometer promises to be a sensitive, accurate , and useful tool to study the spatial variation of soil erosion when magne tic tracers are used. Published by Elsevier Science B.V.