Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: August 28, 2008
Publication Date: N/A
Technical Abstract: In 1968 research began at the USDA ARS Sedimentation Laboratory on the application of fallout radionuclides to determine sediment deposition and soil redistribution rates and patterns in agricultural and natural ecosystems. This research was based on the use of fallout Cesium -137(Cs-137) from nuclear weapon tests deposited worldwide during the 1950's and 1960's. Once Cs-137 reaches the soil surface, it is strongly and quickly adsorbed by soil particles and is essentially nonexchangeable. Thus the movement of Cs-137 across the landscape is associated with the physical processes of soil movement making it an effective tracer of the movement and redeposition of soil particles. Over the past 40 years, research has shown that Cs-137 can be used effectively and efficiently to study the sources and redistribution patterns of soil particles on the landscape. By comparing Cs-137 inventory in a soil profile with a reference soil profile (a nearby soil profile with no soil erosion or deposition), it is possible to determine soil erosion rates or in field deposition. The Cs-137 technique is used to make estimates of soil loss or deposition for a specific soil profile collected in the field giving site specific information on soil loss or gain. This paper gives examples of the application of the method for measuring sediment deposition rates, soil redistribution rates and patterns, and sediment source determination in watersheds. The research in the 1960s and 1970s at the USDA ARS Sedimentation Laboratory provided the basis for the development of these techniques that are now widely used around the world. The unique capability of the Cs-137 methodology for studying soil movement rates and patterns, sediment sources, and sediment deposition rates has much to offer for understanding patterns of soil redistribution on the landscape and for developing management plans to conserve our agricultural and natural resources.