title: Anthropogenic236U and129I in the Mediterranean Sea: First comprehensive distribution and constrain of their sources.
abstract: The first basin-wide distribution of236U/238U atom ratios and129I concentrations is presented for the Mediterranean Sea. During the GEOTRACES GA04S-MedSeA expedition in 2013 seawater was collected from 10 vertical profiles covering the principal sub-basins of the Mediterranean Sea. The main objective was to understand the distributions of236U and129I in relation to the water masses, and to constrain their sources in this region. The236U/238U atom ratios and the129I concentrations ranged from (710±40)×10-12to (2220±60)×10-12and from (4.0±0.1)×107to (13.8±0.3)×107at·kg-1, respectively. The results show that radionuclide-poor Atlantic Water is entering at the surface through the Strait of Gibraltar whereas comparably radionuclide-enriched Levantine Intermediate Water is sinking in the Eastern Basin and flowing westward at intermediate depths. Low radionuclide levels were found in the oldest water masses at about 1000-2000m depth in the Eastern Basin. At greater depths, waters were relatively enriched in236U and129I due to dense water formation occurring in both, the Eastern and Western Basins. The inventories of236U and129I cannot be explained only by global fallout from atmospheric nuclear bomb testings carried out in the 1950s and 1960s. We estimate that the liquid input of236U from the nuclear reprocessing facility of Marcoule (France), via the Rhône river, was of the same order of magnitude than the contribution from global fallout, whereas liquid and gaseous releases of129I from Marcoule were up to two orders of magnitude higher than global fallout. For both radionuclides, the contribution from the Chernobyl accident is found to be minor.
authors.affiliation: Institut de Ciència i Tecnologia Ambientals & Departament de Física, Universitat Autònoma de Barcelona, Bellaterra 08193, Spain. Electronic address: mcastrillejo.sci@gmail.com.
authors.forename: M
authors.initials: M
authors.lastname: Castrillejo
authors.affiliation: Laboratory of Ion Beam Physics, ETH-Zurich, Otto Stern Weg 5, 8093 Zurich, Switzerland; Institute of Biogeochemistry and Pollutant Dynamics, Environmental Physics, ETH-Zurich, Universitätstrasse 16, 8092 Zurich, Switzerland.
authors.forename: N
authors.initials: N
authors.lastname: Casacuberta
authors.affiliation: Laboratory of Ion Beam Physics, ETH-Zurich, Otto Stern Weg 5, 8093 Zurich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Christl
authors.affiliation: Institut de Ciència i Tecnologia Ambientals & Departament de Física, Universitat Autònoma de Barcelona, Bellaterra 08193, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Garcia-Orellana
authors.affiliation: Laboratory of Ion Beam Physics, ETH-Zurich, Otto Stern Weg 5, 8093 Zurich, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Vockenhuber
authors.affiliation: Laboratory of Ion Beam Physics, ETH-Zurich, Otto Stern Weg 5, 8093 Zurich, Switzerland.
authors.forename: H-A
authors.initials: HA
authors.lastname: Synal
authors.affiliation: Institut de Ciència i Tecnologia Ambientals & Departament de Física, Universitat Autònoma de Barcelona, Bellaterra 08193, Spain; School of Science, Centre for Marine Ecosystems Research, Edith Cowan University, Joondalup, WA 6027, Australia; Oceans Institute and School of Physics, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia. Electronic address: pere.masque@uab.cat.
authors.forename: P
authors.initials: P
authors.lastname: Masqué
mesh_terms: D004784:Environmental Monitoring; D005602:France; D007457:Iodine Radioisotopes / Q000032:analysis*; D008522:Mediterranean Sea; D055848:Nuclear Power Plants; D045483:Rivers; D012623:Seawater / Q000737:chemistry*; D014501:Uranium / Q000032:analysis*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D007457:Iodine Radioisotopes; C000615177:Uranium-236; D014875:Water Pollutants, Radioactive; D014501:Uranium
keywords: (129)I; (236)U; Artificial radionuclides; GEOTRACES; Mediterranean Sea