title: Suitability of 239+240Pu and 137Cs as tracers for soil erosion assessment in mountain grasslands.
abstract: Anthropogenic radionuclides have been distributed globally due to nuclear weapons testing, nuclear accidents, nuclear weapons fabrication, and nuclear fuel reprocessing. While the negative consequences of this radioactive contamination are self-evident, the ubiquitous fallout radionuclides (FRNs) distribution form the basis for the use as tracers in ecological studies, namely for soil erosion assessment. Soil erosion is a major threat to mountain ecosystems worldwide. We compare the suitability of the anthropogenic FRNs, 137Cs and 239+240Pu as soil erosion tracers in two alpine valleys of Switzerland (Urseren Valley, Canton Uri, Central Swiss Alps and Val Piora, Ticino, Southern Alps). We sampled reference and potentially erosive sites in transects along both valleys. 137Cs measurements of soil samples were performed with a Li-drifted Germanium detector and 239+240Pu with ICP-MS. Our data indicates a heterogeneous deposition of the 137Cs, since most of the fallout origins from the Chernobyl April/May 1986 accident, when large parts of the European Alps were still snow-covered. In contrast, 239+240Pu fallout originated mainly from 1950s to 1960s atmospheric nuclear weapons tests, resulting in a more homogenous distribution and thus seems to be a more suitable tracer in mountainous grasslands. Soil erosion assessment using 239+240Pu as a tracer pointed to a huge dynamic and high heterogeneity of erosive processes (between sedimentation of 1.9 and 7 t ha(-1) yr(-1) and erosion of 0.2-16.4 t ha(-1) yr(-1) in the Urseren Valley and sedimentation of 0.4-20.3 t ha(-1) yr(-1) and erosion of 0.1-16.4 t ha(-1) yr(-1) at Val Piora). Our study represents a novel and successful application of 239+240Pu as a tracer of soil erosion in a mountain environment.
authors.affiliation: Environmental Geosciences, University of Basel, Bernoullistr. 30, 4056 Basel, Switzerland. Electronic address: christine.alewell@unibas.ch.
authors.forename: Christine
authors.initials: C
authors.lastname: Alewell
authors.affiliation: Environmental Geosciences, University of Basel, Bernoullistr. 30, 4056 Basel, Switzerland. Electronic address: katrin.meusburger@unibas.ch.
authors.forename: Katrin
authors.initials: K
authors.lastname: Meusburger
authors.affiliation: Environmental Geosciences, University of Basel, Bernoullistr. 30, 4056 Basel, Switzerland. Electronic address: gregor.juretzko@unibas.ch.
authors.forename: Gregor
authors.initials: G
authors.lastname: Juretzko
authors.affiliation: Soil and Water Management & Crop Nutrition Laboratory, FAO/IAEA Agriculture & Biotechnology Laboratory, PO Box 100, Wagramerstrasse 5, A-1400 Vienna, Austria. Electronic address: l.mabit@iaea.org.
authors.forename: Lionel
authors.initials: L
authors.lastname: Mabit
authors.affiliation: Chemistry and Biochemistry, Northern Arizona University, Box 5698, Flagstaff, AZ 86011-5698, USA. Electronic address: Michael.Ketterer@nau.edu.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Ketterer
mesh_terms: D002588:Cesium Radioisotopes / Q000032:analysis*; D017753:Ecosystem; D011005:Plutonium / Q000032:analysis*; D006109:Poaceae; D011847:Radioactive Fallout / Q000032:analysis*; D018788:Radioactive Hazard Release; D011849:Radioactive Tracers; D012987:Soil / Q000737:chemistry*; D012990:Soil Pollutants, Radioactive / Q000032:analysis*; D013557:Switzerland
chemical_list: D002588:Cesium Radioisotopes; D011847:Radioactive Fallout; D011849:Radioactive Tracers; D012987:Soil; D012990:Soil Pollutants, Radioactive; D011005:Plutonium
keywords: Caesium; European Alps; Fallout radionuclides; Plutonium; Soil degradation