Using Rare-Earth Oxide Tracers for Studying Soil Erosion Dynamics

Abstract

ABSTRACTthese 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 erosion soil erosion dynamics. Dynamically varied, spatially distributed erosion 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 mixingVarious 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 137 Cs this technique to study soil erosion dynamics. Five REE oxide powders (Ritchie and McHenry, 1990; Walling and He, 1999 Pb provide little information on sediment origin. better understand soil erosion dynamics, but also for Unlike bomb-produced and cosmogenic radionuthorough validation of process-based erosion models.clides, radioactive elements can be manipulated and Spatially distributed soil erosion data are also useful deliberately introduced to study soil erosion. A major for evaluating on-site impacts such as effects of soil concern with this type of tracer is the radiological risk redistribution on crop yields and off-site impacts includto researchers and the environment. Exotic particles ing sediment origin and destination. Many processsuch as fluorescent glass or magnetic plastic beads have based erosion prediction models have been developed been used to overcome this concern, but suffer other in the past several decades to predict soil erosion at serious shortcomings. Major criticisms for exotic partivarious temporal and spatial scales (Nearing et al., 1989; cles are that (i) these particles may not bind with soil Hairsine and Rose, 1992; Borah, 1989). Since erosion particles or soil aggregates and therefore are transprocesses constantly change in time and space, processported separately; (ii) exotic particles differ in size distribased models have advantages over spatially and tempobution, particle density, shape, surface morphology, and rally lumped empirical prediction models. Element Applicationwith silt fractions. They also developed and tested a A wooden box (4 by 4 m) with adjustable slope was quick acid-leaching method for extracting REEs from used in the study. The box was arbitrarily set to a 10% soil and sediment samples for analysis by ICPMS. The slope, partially because it is close to the standard 9% quick extraction method makes it possible to take full slope used for developing the Universal Soil Loss Equaadvantage of this new technology. The advantages of tion. The sieved soil was packed into the soil box to a ICPMS as identified by Jarvis (1989) include exceptional depth of 0.2 m over a 0.5-m sand layer, wh...

Tracing sediment dynamics and sources in eroding rills with rare earth elements

“…This potential of REEs for soil erosion tracing was demonstrated in laboratory flume experiments by Zhang et al . (2003) and Polyakov & Nearing (2004).…”

Underutilized biogeochemical tracers distinguish invertebrate populations in a complex river system

“…REEs have low solubility, therefore sediment and fine suspended particles are the primary sinks or reservoirs for REE in aquatic environments (Khan et al ). These properties, in combination with their predictable and consistent cycling patterns, mean REE are excellent geochemical tracers and are regularly used to identify sources of eroded sediment (Zhang et al , Stevens and Quinton ). Our work suggests these properties also make REE excellent biochemical tracers that can link species with specific geochemical environments.…”

Estimation of the detachment rate in eroding rills in flume experiments using an REE tracing method

“…Currently, typical methods estimate soil erosion as a temporally and spatially integrated quantity by comparing the eroded state after rainfall with the initial soil state, or by collecting eroded and transported materials. Many attempts (Zhang et al 2003;Lei et al, 2006) have been made to use tracers to obtain spatially distributed erosion data. The rare earth elements (REEs) may be suitable for sediment source studies.…”

“…Potential REE candidates for tracing soil erosion were demonstrated in laboratory flume experiments by Zhang et al (2003), , and Lei et al (2006). Ideal REE tracers used for the study of soil erosion and sediment sources should have the following characteristics: 1) they should be capable of being strongly bound to soil particles or of being easily incorporated into aggregates; 2) they should not interfere with sediment detachment and transportation processes; 3) they should be easy, and inexpensive, to use and measure; 4) they should have low background concentrations in soils; 5) they should not be easily taken up by plants nor leached by water; and 6) they should be environmentally friendly (Riebe, 1995;Zhang et al, 2001).…”