Plutonium as a tracer for soil erosion assessment in northeast China

Soil erosion is one of the most serious environmental and agricultural problems faced by human society. Assessing intensity is an important issue for controlling soil erosion and improving eco-environmental quality. The suitability of the application of plutonium (Pu) as a tracer for soil erosion assessment in northeast China was investigated by comparing with that of Cs-137. Here we build on preliminary work, in which we investigated the potential of Pu as a soil erosion tracer by sampling additional reference sites and potential erosive sites, along the Liaodong Bay region in northeast China, for Pu isotopes and Cs-137. Pu-240/Pu-239 atomic ratios in all samples were approximately 0.18, which indicated that the dominant source of Pu was the global fallout. Pu showed very similar distribution patterns to those of Cs-137 at both uncultivated and cultivated sites. Pu239 + 240 concentrations in all uncultivated soil cores followed an exponential decline with soil depth, whereas at cultivated sites, Pu was homogenously distributed in plow horizons. Factors such as planted crop types, as well as methods and frequencies of irrigation and tillage were suggested to influence the distribution of radionuclides in cultivated land. The baseline inventories of Pu239 + 240 and Cs-137 were 88.4 and 1688 Bq m(-2) respectively. Soil erosion rates estimated by Pu239 + 240 tracing method were consistent with those obtained by the Cs-137 method, confirming that Pu is an effective tracer with a similar tracing behavior to that of Cs-137 for soil erosion assessment. (C) 2014 Elsevier B.V. All rights reserved.