title: An estimate of the inventory of technetium-99 in the sub-tidal sediments of the Irish Sea.
abstract: Published results from earlier studies have provided indications that measurable quantities of technetium-99 ((99)Tc) have accumulated in the sub-tidal sediments of the Irish Sea. This is due to the enhanced discharges from the Sellafield nuclear reprocessing plant in Cumbria, UK (between 1994 and 2004). Depth distributions of (99)Tc concentrations in sub-tidal sediments have been determined from a limited number of Irish Sea sites, following the collection of deep sediment cores (up to 2 m in depth), sampled in two research cruise surveys in 2005 and 2006. Vertical concentration profiles of (99)Tc from a range of substrates in the Irish Sea are presented here and these have been used to produce an estimate of the total inventory of (99)Tc residing in the sub-tidal sediments of the Irish Sea. Significant variation was observed between (99)Tc concentrations in the sediment samples, as well as in the shape of individual depth profiles. As anticipated, concentrations tended to be greater on fine-grained (muddy) substrates and showed a general decrease with distance from Sellafield. Vertical concentration profiles of (137)Cs, and (137)Cs data from published work, have also been considered to evaluate the use of the relatively few (99)Tc core data (upon which to determine the (99)Tc inventory). The inventories of (99)Tc and (137)Cs are estimated to have been of the order of 30 and 455 terabecquerels (TBq), respectively, or ∼2% of the total cumulative Sellafield discharge for each of the two radionuclides. The residence half-time of (137)Cs in the sub-tidal sediments of the Irish Sea is estimated to be in the order of ∼16 years. Therefore, as the Kd values for (99)Tc and (137)Cs are similar, this also provides an indicative value to predict future losses of (99)Tc from the sediment reservoir.
authors.affiliation: Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK.
authors.forename: Stuart B
authors.initials: SB
authors.lastname: Jenkinson
authors.affiliation: Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK.
authors.forename: David
authors.initials: D
authors.lastname: McCubbin
authors.affiliation: Food Standards Agency, Aviation House, 125 Kingsway, London WC2B 6NH, UK.
authors.forename: Paul H W
authors.initials: PH
authors.lastname: Kennedy
authors.affiliation: Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK.
authors.forename: Alastair
authors.initials: A
authors.lastname: Dewar
authors.affiliation: Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK.
authors.forename: Rachel
authors.initials: R
authors.lastname: Bonfield
authors.affiliation: Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK. Electronic address: kins.leonard@cefas.co.uk.
authors.forename: Kinson S
authors.initials: KS
authors.lastname: Leonard
mesh_terms: D002588:Cesium Radioisotopes / Q000032:analysis; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000032:analysis*; D009792:Oceans and Seas; D013667:Technetium / Q000032:analysis*; D014875:Water Pollutants, Radioactive / Q000032:analysis
chemical_list: D002588:Cesium Radioisotopes; D014875:Water Pollutants, Radioactive; D013667:Technetium
keywords: (99)Tc; Inventory; Irish Sea; Sediments; Technetium-99