Application of Radioactive Fallout Cesium-137 for Measuring Soil Erosion and Sediment Accumulation Rates and Patterns: A Review

Radioactive fallout 137CS (cesium-137) deposited across the landscape from atmospheric nuclear tests is strongly absorbed on soil particles limiting its movement by chemical and biological processes. Most 137CS movement in the environment is by physical processes; therefore, 137CS is a unique tracer for studying erosion and sedimentation. Cesium-137 loss from a watershed has been shown to correlate strongly with soil loss calculated by the Universal Soil Loss Equation (USLE) or measured from small runoff plates. By measuring spatial patterns or 137CS in vertical and horizontal planes across the landscape, rates or soil loss or deposition can be measured for different parts or a watershed. Even within landscape units, redistribution or soil can be mapped and erosion or deposition rates for different parts or individual fields measured and mapped. Sediment accumulation rates can be measured by comparing the vertical distribution or 137CS in sediments with the temporal deposition or fallout 137CS from the atmosphere to locate sediment horizons. Using these dated sediment horizons, sediment accumulation rates can be measured. Interpretations about the location or these dated horizons must consider particle size or the sediments, reworking or deposited sediments, diffusional movement or 137CS, and time rates or physical process in the sedimentation process. The 137CS technique can be used to determine sediment accumulation rates in a wide variety or depositional environments including reservoirs, lakes, wetlands, coastal areas, and floodplains. The bibliography shows that 137CS has been used widely for studying erosion and sedimentation in many different environments around the world. Radioactive fallout 137CS has been used as a tracer to provide independent information on erosion and sedimentation rates and patterns. Sedimentation and sediment accumulation in this paper is used to indicate a vertical deposition of sediments (cm yr1). The purpose of this article is to review the development and application of a technique using radioactive fallout 137CS to measure rates and patterns of erosion and sedimentation. A bibliography is also provided.