Contents lists available at ScienceDirect Nuclear Inst. and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb 129 I concentration in a high-mountain environment Sarah Kamleitner a, ⁎ , Johannes Lachner b , Peter Steier b , Stephan M. Weise c , Sabine Kraushaar a a University of Vienna, Department of Geography and Regional Research, Vienna, Austria b University of Vienna, Isotope Research and Nuclear Physics, Vienna, Austria c UFZ-Helmholtz Center for Environmental Science, Halle, Germany ARTICLEINFO Keywords: Anthropogenic radionuclide Proglacial Lateral moraines European Alps Kaunertal Valley Altitude gradient Dating Tritium ABSTRACT The environmental abundance of 129 I has been signifcantly increased in the Nuclear Age starting from the 1950s. Tons of anthropogenic 129 I have been discharged into the environment through anthropogenic nuclear activities.Thisfactallowstherelativedatingofspringwatersamples,wherelowconcentrationsof 129 Iindicate waterswithnosurfacecontactsincethe50s.Inthisregard,thepresentstudyaimstoidentifytherelativeageof spring waters in the Kaunertal Valley in Western Austria. More than ffty water samples were derived from precipitation collectors, springs, and directly from the Gepatschferner glacier. Measurement results cover 129 I concentrationsrangingfrom1×10 6 to5×10 8 atomsperlitre.Thevariabilityofsixsprings,whichweretested in July and September, was found to be negligible given the associated measurement uncertainties. No altitu- dinal dependence was found along the topographic gradient. Signifcant diferences between high 129 I con- centrationsofprecipitationandlow 129 Icontentsofglaciersampleswerefoundandareconsideredbenefcialto ascribespringwaterstopre-nuclear(olderthan1950)ormoderntimesofformation.Additionaltritiumanalyses of selected water samples partly support the usage of 129 I for relative dating. 1. Introduction 129 I is iodine’s only long-lived radioisotope and has a half-life of 15.7Ma. It is naturally produced by the interaction of stable xenon isotopes with high energy cosmic ray particles in the stratosphere and via spontaneous fssion of uranium 238 in the lithosphere and oceans [18,43,53,49,17].Theearth’stotalnatural 129 Iinventorywasestimated tobe∼50tons [37].Themajorityisboundwithinthelithosphereand only a small fraction of ∼250kg is available in the hydrosphere, at- mosphere, and biosphere [18,25]. The natural 129 I background con- centrationsforoceanandfreshwaterwerepostulatedonthebasisofthe assumed initial 129 I/I ratio and average concentration of the stable isotope 127 Iamountedupto4.4×10 5 and3.7×10 4 atoms/L respec- tively [53]. No initial 129 I values for the terrestrial environment exist since the ultra-low concentrations in terrestrial samples remain a challenge to detect [18]. Before 1950 129 Iconcentrationscanbeestimatedtobeinanatural equilibrium. Emissions from nuclear weapon tests, nuclear accidents, and above all nuclear reprocessing facilities have increased the initial backgroundvaluesbythreetoeightordersofmagnitudeinatmosphere, hydrosphere, and biosphere [37,25],(Fig. 1). Anthropogenic 129 I is easily detectable in waters anywhere in the Northern hemisphere [23] and has been marked even in remote background zones such as Antarctica [52]. Today, point source emissions dominate the spatial distribution of 129 I [53,2,19,45]. Especially European reprocessing plants, such as Sellafeld/Windscale (operating since 1951), former Marcoule (1959), and LaHague (1965) [53] are by far the greatest source of anthro- pogeniciodineemissions.Theirestimatedgaseousandliquiddischarge amountstoabove5600kgsincetheircommissioninginthe50sand60s uptotheyear2007 [53,25].Oceanshavealwaysbeenamainsourceof iodineforcontinentalEurope [24,55],andaretodayhighlyafectedby liquid emissions of Sellafeld and LaHague [13,43,53,2,24]. Roughly 99% of Europe’s 129 I emissions are released into the Irish Sea and the English Channel [45]. DuringthetransportofairmassesfromtheoceanstotheEuropean continent iodine concentrations, just as any isotopic composition, are altered due to several factors, such as latitude efects, continental ef- fects,amountefects,altitudeefectsorseasonalefects [58,38].Iodine concentrations in particular are expected to decrease with increasing distance from the ocean [27,3,17] and from nuclear reprocessing fa- cilities [27],withincreasingaltitude [29,45,17] andwithtimeduringa single rain event [17]. Fabryka-Martin [17] ascribes the continentality efect due to the removal of iodine by wet and dry deposition or the convectivemixingofairmasses.Thealtitudedependencyisenforcedby orographic lifting and cloud scavenging, when air masses strike https://doi.org/10.1016/j.nimb.2019.05.003 Received 31 January 2018; Received in revised form 2 April 2019; Accepted 1 May 2019 ⁎ Corresponding author. E-mail address: kamsarah@phys.ethz.ch (S. Kamleitner). Nuclear Inst. and Methods in Physics Research B xxx (xxxx) xxx–xxx 0168-583X/ © 2019 Elsevier B.V. All rights reserved. Please cite this article as: Sarah Kamleitner, et al., Nuclear Inst. and Methods in Physics Research B, https://doi.org/10.1016/j.nimb.2019.05.003