Using rare-earth oxide tracers for studying soil erosion dynamics

ABSTRACT these advantages will not be fully recognized unless the spatial and temporal predictability of process-basedSpatially averaged soil erosion data provide little information on models are validated. Thus, spatially distributed erosionsoil erosion dynamics. Dynamically varied, spatially distributed ero-sion data are needed to better understand erosion processes and data are of great importance in advancing process-based thoroughly evaluate process-based erosion prediction models. The erosion prediction models. objectives of this study are to examine the feasibility of direct mixing Various types of tracers have been developed and rare-earth element (REE) oxides with soil materials to trace soil used to obtain spatially distributed data. Commonly used erosion at a plot scale and to explore further the potential of using tracers include atomic bomb fallout radionuclide 137Cs this technique to study soil erosion dynamics. Five REE oxide powders (Ritchie and McHenry, 1990; Walling and He, 1999), were mixed with a Camden silt soil (fine, silty, mixed, mesic Typic naturally occurring radionuclides 210Pb, 7Be, and 234ThHapludalt) at five slope positions. Six rainstorms were applied to a (Wallbrink and Murray, 1993), deliberately introduced4 by 4 m soil bed at a 10 % slope. Runoff was collected during the radionuclides such as 56Fe and 60Co (Wooldridge, 1965;rains and surface soil was sampled after each rain. All samples were Toth and Alderfer, 1960), noble element (e.g., Au orextracted for REE with a quick acid-leaching method and extracts were analyzed by inductively coupled plasma mass spectrometry Ag)-labeled natural particles (Olmez et al., 1994), REE