title: A multi-radionuclide approach to evaluate the suitability of (239+240)Pu as soil erosion tracer.
abstract: Fallout radionuclides have been used successfully worldwide as tracers for soil erosion, but relatively few studies exploit the full potential of plutonium (Pu) isotopes. Hence, this study aims to explore the suitability of the plutonium isotopes (239)Pu and (240)Pu as a method to assess soil erosion magnitude by comparison to more established fallout radionuclides such as (137)Cs and (210)Pbex. As test area an erosion affected headwater catchment of the Lake Soyang (South Korea) was selected. All three fallout radionuclides confirmed high erosion rates for agricultural sites (>25tha(-1)yr(-1)). Pu isotopes further allowed determining the origin of the fallout. Both (240)Pu/(239)Pu atomic ratios and (239+240)Pu/(137)Cs activity ratios were close to the global fallout ratio. However, the depth profile of the (239+240)Pu/(137)Cs activity ratios in undisturbed sites showed lower ratios in the top soil increments, which might be due to higher migration rates of (239+240)Pu. The activity ratios further indicated preferential transport of (137)Cs from eroded sites (higher ratio compared to the global fallout) to the depositional sites (smaller ratio). As such the (239+240)Pu/(137)Cs activity ratio offered a new approach to parameterize a particle size correction factor that can be applied when both (137)Cs and (239+240)Pu have the same fallout source. Implementing this particle size correction factor in the conversion of (137)Cs inventories resulted in comparable estimates of soil loss for (137)Cs and (239+240)Pu. The comparison among the different fallout radionuclides highlights the suitability of (239+240)Pu through less preferential transport compared to (137)Cs and the possibility to gain information regarding the origin of the fallout. In conclusion, (239+240)Pu is a promising soil erosion tracer, however, since the behaviour i.e. vertical migration in the soil and lateral transport during water erosion was shown to differ from that of (137)Cs, there is a clear need for a wider agro-environmental testing.
authors.affiliation: Environmental Geosciences, University of Basel, Bernoullistrasse 30, CH-4056 Basel, Switzerland. Electronic address: Katrin.Meusburger@unibas.ch.
authors.forename: Katrin
authors.initials: K
authors.lastname: Meusburger
authors.affiliation: Soil and Water Management and Crop Nutrition Laboratory, FAO/IAEA Agriculture & Biotechnology Laboratory, IAEA Laboratories, Seibersdorf, Austria. Electronic address: L.Mabit@iaea.org.
authors.forename: Lionel
authors.initials: L
authors.lastname: Mabit
authors.affiliation: Chemistry Department, Metropolitan State University of Denver, CO, USA. Electronic address: mkettere@msudenver.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Ketterer
authors.affiliation: Department of Environmental Science & Engineering, Ewha Womans University, Seoul 120-750, Republic of Korea. Electronic address: jhp@ewha.ac.kr.
authors.forename: Ji-Hyung
authors.initials: JH
authors.lastname: Park
authors.affiliation: Radioanalytical Reference Laboratory, Central Agricultural Office Food and Feed Safety Directorate, Hungary.
authors.forename: Tarjan
authors.initials: T
authors.lastname: Sandor
authors.affiliation: Dipartimento di AGRARIA, Università degli Studi "Mediterranea" di Reggio Calabria, Italy. Electronic address: paolo.porto@unirc.it.
authors.forename: Paolo
authors.initials: P
authors.lastname: Porto
authors.affiliation: Environmental Geosciences, University of Basel, Bernoullistrasse 30, CH-4056 Basel, Switzerland. Electronic address: Christine.Alewell@unibas.ch.
authors.forename: Christine
authors.initials: C
authors.lastname: Alewell
mesh_terms: D000383:Agriculture; D002588:Cesium Radioisotopes / Q000032:analysis; D016468:Forestry; D008962:Models, Theoretical; D011005:Plutonium / Q000032:analysis*; D011834:Radiation Monitoring / Q000379:methods*; D056910:Republic of Korea; D012987:Soil; D012989:Soil Pollutants / Q000032:analysis*
chemical_list: D002588:Cesium Radioisotopes; C000615188:Plutonium-240; D012987:Soil; D012989:Soil Pollutants; C000614989:Cesium-137; D011005:Plutonium; C000615187:Plutonium-239
keywords: (210)Pb(ex); (239+240)Pu/(137)Cs activity ratio; Conversion models; MODERN; Particle size correction factor; South Korea