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United States Department of Agriculture

Agricultural Research Service

Title: Tracing Soil Erosion and Soil Aggregation with Rare Earth Oxides

Authors
item Zhang, Xunchang
item Nearing, Mark
item Norton, Lloyd

Submitted to: Soil Erosion for 21st Century Symposium
Publication Type: Proceedings
Publication Acceptance Date: January 3, 2001
Publication Date: January 3, 2001

Interpretive Summary: Soil erosion by water and wind is a worldwide problem. It deteriorates our precious land, soil, and water resources and therefore adversely affects our agricultural production and environmental quality. To minimize the adverse effects and to promote agricultural productivity and sustainability, soil erosion must be controlled. To do so, we must know how soils are eroded and transported by water and wind within a farm field and where the eroded sediments come from. The purpose of this work is to develop and test a new method, which can be used to tag soil materials at various locations with different non-hazardous chemicals, called rare earth elements. The results showed that those chemical elements were strongly bound with soil materials, easy and inexpensive to measure, and environmentally safe. Those rare earth elements are ideal tracers to track down sediment movement in a field. This work has provided soil erosion scientists and soil conservationists a new method for determining sediment source areas, that is, where sediments are coming from and how much. This information can be used by scientists to revise or calibrate soil erosion prediction tools. It can also be used by soil conservationists and farmers to lay out site-specific management practices to combat soil erosion.

Technical Abstract: Spatially distributed soil erosion data are needed to thoroughly validate physically based erosion prediction models and to fully understand soil erosion dynamics. Most of the existing soil loss data are spatially lumped. The objectives of this study were to evaluate the feasibility of direct use of rare earth element (REE) oxides as tracers for soil erosion studies by examining their binding ability with soil materials. Five REE oxide powders were directly mixed with the Miami soil and were leached with deionized water in a soil box. Following leaching, soil was sectioned in 25-mm intervals. The REE-tagged soil was wet sieved to obtain REE concentrations in each size group. A proposed acid- leaching method was used to extract REEs and all extracts were analyzed by an ICP-MS. The proposed extraction procedure was simple and consistent, with the maximum CV being around 11% for all REEs. REE oxides were uniformly incorporated into soil aggregates of different sizes (> 53 um) and were bound with silt-size particles. This finding shows the direct use of REE oxides is superior to other REE-tagged particulate tracers, because it eliminates the needs of tagging exotic particles with REEs. More importantly, the direct mixing of a trace amount of REEs doesn't alter physicochemical properties of soil particles and aggregates. This work has shown that REE oxides are ideal tracers for studying soil translocation at various scales including soil aggregation, bioturbation, and upland soil erosion by water.

Last Modified: 11/20/2014
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