Manmade and natural radionuclides in north east Atlantic shelf and slope sediments: Implications for rates of sedimentary processes and for contaminant dispersion

A B MacKenzie, A Stewart, G T Cook, L Mitchell, D J Ellet, Colin Griffiths

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Results are presented for a study of manmade and natural radionuclides in north east Atlantic continental shelf and slope sediments to the west of Scotland. The data are interpreted in the context of sediment mixing and accumulation processes and are used to establish the westward extent of contamination of the sediment system. Offshore shelf and slope sediments were found to have post-glacial sedimentation rates of the order of 1 cm ky(-1) but nearshore sediments had much higher accumulation rates of the order of 0.1 cm y(-1). Surface mixed layer depths of up to 6 cm were observed and non-local mixing affected most of the slope sediments, resulting in advective transport of surface sediment to depths of up to 10 cm. Biodiffusion coefficients for offshore shelf and slope sediments were dominantly in the range 10(-8) to 10(-9) cm(2) s(-1). The study confirmed that seawater contaminated with Sellafield waste radionuclides is dominantly entrained to the cast of 7 degrees W and, consistent with this, higher levels of Sellafield derived radionuclides were confined to nearshore sediments, with lower levels to the west of 7 degrees W. Pu-238/Pu-239,Pu-240 data indicated that Sellafield contributed 75-91% of the total plutonium in coastal sediment but only about 4-8% of the total in slope sediments. By analogy, it can be concluded that a similar situation will apply to other contaminants in seawater entering the north east Atlantic via the North Channel. (c) 2006 Elsevier B.V. All rights reserved.
Original languageEnglish
Pages (from-to)256-272
Number of pages17
JournalSCI TOTAL ENVIRON
Volume369
Issue number1-3
DOIs
Publication statusPublished - 2006

Keywords

  • BIOLOGICAL-ACTIVITY
  • Environmental Sciences
  • CONTINENTAL-SLOPE
  • SELLAFIELD WASTE
  • NE ATLANTIC
  • IRISH SEA SEDIMENTS
  • PLUTONIUM
  • PB-210
  • MARINE-SEDIMENTS
  • COASTAL SEDIMENTS
  • MIXING RATES

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