title: Distribution of natural and anthropogenic radionuclides in northwest Mediterranean coastal sediments.
abstract: The distribution of radionuclides in NW Mediterranean coastal sediments, and the processes controlling their abundance were investigated in three cores taken near the island of Porquerolles and one offshore Monaco. The sediments collected near Porquerolles were strongly anoxic due to diagenetic processes involved in the decomposition of organic matter, whereas they transitioned from oxic to anoxic at a depth of 4 cm beneath the seawater interface at Monaco. Organic carbon (OC) was more abundant in sediments at Porquerolles (by about a factor of 3-5) than at Monaco and elsewhere in the coastal NW Mediterranean. Sediment cores collected NE of Porquerolles also possessed elevated uranium concentrations that correlated with high OC content and strong reducing conditions. The239,240Pu and241Am activities in surficial sediments ranged from 1 to 5.7 Bq kg-1and 0.3 to 1 Bq kg-1, respectively, while the137Cs activity ranged from 0.3 to 6.2 Bq kg-1. The mean activity ratios of241Am/239,240Pu and238Pu/239,240Pu in Porquerolles and Monaco sediments were similar to the global fallout ratios. Sediment inventories of global fallout239,240Pu (430-800 Bq m-2) and241Am (150-285 Bq m-2) were by about a factor of 5-10 higher at Porquerolles, whereas the inventory of137Cs (430-1000 Bq m-2) was substantially lower at the investigated stations than have been reported elsewhere at similar latitudes. Specific local conditions characterised by high OC sediment loads due to the growth and mortality of Posidonia oceanica have been responsible for deposition of large amounts of seagrass tissues at the NE corner of Porquerolles, which have had a profound effect on the distribution of radionuclides in the sediments.
authors.affiliation: Korea Research Institute of Standards and Science, Daejeon, Republic of Korea. Electronic address: s.lee@kriss.re.kr.
authors.forename: Sang-Han
authors.initials: SH
authors.lastname: Lee
authors.affiliation: Comenius University, Faculty of Mathematics, Physics and Informatics, Bratislava, Slovakia.
authors.forename: Pavel P
authors.initials: PP
authors.lastname: Povinec
authors.affiliation: International Atomic Energy Agency, Environment Laboratories, Monaco.
authors.forename: John R M
authors.initials: JRM
authors.lastname: Chisholm
authors.affiliation: Scientific Centre of Monaco, Monaco.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Levy
authors.affiliation: International Atomic Energy Agency, Environment Laboratories, Monaco.
authors.forename: Juan-Carlos
authors.initials: JC
authors.lastname: Miquel
authors.affiliation: Korea Research Institute of Standards and Science, Daejeon, Republic of Korea.
authors.forename: Jung-Suk
authors.initials: JS
authors.lastname: Oh
mesh_terms: D001417:Background Radiation; D008522:Mediterranean Sea; D011834:Radiation Monitoring; D012623:Seawater / Q000737:chemistry*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D014875:Water Pollutants, Radioactive
keywords: Anthropogenic radionuclides; Coastal sediments; Global fallout; Sediment inventories; Uranium isotopes