Using Rare‐Earth Oxide Tracers for Studying Soil Erosion Dynamics

Abstract

Spatially averaged soil erosion data provide little information on soil erosion dynamics. Dynamically varied, spatially distributed erosion data are needed to better understand erosion processes and thoroughly evaluate process‐based erosion prediction models. The objectives of this study are to examine the feasibility of direct mixing rare‐earth element (REE) oxides with soil materials to trace soil erosion at a plot scale and to explore further the potential of using this technique to study soil erosion dynamics. Five REE oxide powders were mixed with a Camden silt soil (fine, silty, mixed, mesic Typic Hapludalt) at five slope positions. Six rainstorms were applied to a 4 by 4 m soil bed at a 10% slope. Runoff was collected during the rains and surface soil was sampled after each rain. All samples were extracted for REE with a quick acid‐leaching method and extracts were analyzed by inductively coupled plasma mass spectrometry (ICPMS). Mean error of REE‐derived sediment discharge relative to measured total across six rainstorms was 14.5%. Our results demonstrate that the REE‐tracing technique is feasible and sound, being capable of producing both spatially and temporally distributed erosion data. Results indicate that the most severe erosion occurred in the upper middle section of a uniform slope, and total sediment delivery from each segment was positively related to amounts of sediment deposition on the entire slope from that segment. This technique has the potential to bring new perspectives to soil erosion research.