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field_methods:cesium_cs_-137_in_erosion_and_deposition_analysis [2013/10/14 17:47] (current)
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 +====== Cesium (Cs)-137 in Erosion and Deposition Analysis ======
 +Written by Grant Hamilton
 +===== Cs-137 =====
 +Cs-137 is a radioactive isotope of cesium. ​ Its occurrence is the result of anthropogenic nuclear fission. ​ Most of the Cs-137 present in the environment is the result of fallout from nuclear weapons testing during the Cold War.  Cs-137 first reached detectable levels in 1954.  Additional fallout occurred with the Chernobyl and Fukushima nuclear power plant disasters. ​ Cs-137 is distributed primarily by rainfall, and is readily absorbed by soil.  Cesium-137 decays to barium-137 which then decays to a non-radioactive form of barium. ​ Cs-137 has a half-life of 30.17 years. ​ The measure of Cs-137 concentration is the SI unit of radioactivity,​ the Becquerel (Bq) per kg or m<​sup>​2</​sup>​.  ​
 +=====  Rangeland Applications =====
 +Soil loss can be studied using a technique called radiological fingerprinting to determine the source of suspended sediment in a watershed or the source of a soil deposit. ​ This method can also be used to estimate erosion and deposition rates. ​ Despite regional variations in precipitation,​ the worldwide distribution of Cs-137 was uniform after levels peaked in the late 1980s following the Chernobyl meltdown (the impact of the Fukushima disaster on global Cs-137 levels is a subject of current study). ​ Thus an arid environment'​s baseline Cs-137 level would be the same as that of a wetter region. ​ Higher levels of Cs-137 in a soil sample indicate areas where deposition has occurred and lower levels indicate areas where erosion has occurred.  ​
 +===== Procedure =====
 +Samples can be collected from the soil using a bucket corer or as a suspension in waterways. ​ Sampling sites should be georeferenced using a GPS.  In the laboratory samples are air dried or baked, disaggregated,​ and sieved through 2 mm mesh.  Cs-137 concentrations are measured using a gamma-ray spectrometer. ​ Cs-137 levels are compared with locations throughout the study area to determine sources of deposits. ​ This method has been used in a variety of settings throughout the world.  ​
 +===== Use in Rangeland Settings =====
 +Nearing et al. (2005) used this method to compare the erosion rates in two watersheds within USDA Agricultural Research Service (ARS) experimental ranges in Arizona. ​ In a follow up study, Ritchie et al. (2009) used the Diffusion and Migration Model for Erosion and Deposition on Undisturbed Soils to account for the redistribution of Cs-137 within one of those watersheds.
 +===== References =====
 +Nearing, M.A., Kimoto, A., Nichols, M.H., Ritchie, J.C. (2005). Spatial patterns of soil erosion and deposition in two small, semiarid watersheds. //Journal of Geophysical Research//. Vol. 110. doi: 0.1029/​2005JF000290
 +  * Compared erosion rates of two Arizona watersheds using Cs-137 inventory.  ​
 +Ritchie, J., Nearing, M.A., Rhoton, F.E. (2009). Sediment budgets and source determinations using fallout Cesium-137 in a semiarid rangeland watershed, Arizona, USA. //Journal of Environmental Radioactivity//​. doi: 10.1016/​j.jenvrad.2009.05.008.​unit/​publications/​PDFfiles/​2012.pdf‎
 +  * This is a follow up to the study listed above.
 +U.S. Environmental Protection Agency. (2012). //Cesium//. http://​​radiation/​radionuclides/​cesium.html
 +  * General information about the element cesium. ​
 +Walling, D.E. and He, Q. (1999). Improved models for estimating soil erosion rates from cesium-137 measurements. //Journal of Environmental Quality//. 28(2), pp. 611-622. doi:​10.2134/​jeq1999.00472425002800020027x
 +  * Presents the Diffusion and Migration Model for Erosion and Deposition on Undisturbed Soils. ​
 +Yusheng, Z. (n.d.). //​Applications of Caesium-137 in Soil Erosion and Sedimentation Studies (an introduction)//​. Department of Geography, University of Exeter. http://​​yszhang/​caesium/​welcome.htm
 +  * Brief overview of the Cs-137 process with an extensive list of the literature on the subject.
 +===== Discussion/​Comments =====
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field_methods/cesium_cs_-137_in_erosion_and_deposition_analysis.txt · Last modified: 2013/10/14 17:47 by jgh