Scavenging of 234Th in the Eastern Irish Sea

Kershaw, Peter; Young, A.K.

doi:10.1016/0265-931x(88)90064-1

Cited by 49 publications

(21 citation statements)

References 28 publications

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“…A possible reason for the difference could be a different sediment composition since the samples are not collected from the same location. According to Kershaw and Young (1988) the additional anthropogenic contribution of 238 U from Sellafield and Marchon is 8e15%. Assuming that the isotopic ratio of the Magnox fuel is in the range of 10 À4 (Hamilton and Stevens,1985), we see a contribution of about 10% along the core.…”

Section: Resultsmentioning

confidence: 99%

Determination of U, Pu and Am isotopes in Irish Sea sediment by a combination of AMS and radiometric methods

Srncik¹,

Hrnecek²,

Steier³

et al. 2011

Journal of Environmental Radioactivity

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Section: Resultsmentioning

confidence: 99%

Determination of U, Pu and Am isotopes in Irish Sea sediment by a combination of AMS and radiometric methods

Srncik¹,

Hrnecek²,

Steier³

et al. 2011

Journal of Environmental Radioactivity

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“…Measurements of 234Th/238U disequilibria in filtered seawater, suspended particulate and sea-bed sediment [5,6) provided information on dissolved 23 4 Th scavenging rates and mean particle residence times, indicating that the removal of 234Th was not limited by the rate of adsorption and there was sufficient time to establish an equilibrium K D • This supported the use of the KD approximation in the model for other particle-reactive nuclides.…”

Section: Model Simulations Using Naturally-occurring Radionuclidesmentioning

confidence: 87%

“…Measured sea-bed inventories of unsupported 234Th indicated that enhanced scavenging occurred in the shallower « 25-30 m) water of the eastern Irish Sea [5,6]. Therefore, higher suspended loads were given to those interface boxes in regions where the mean depth of the water box was less than 20 m. This increased the scavenging capacity of these box regions and raised the sea-bed 234Th inventories, but it was not possible to reproduce the observed high sea-bed inventories whilst maintaining the observed 234Th water concentrations.…”

Section: Model Simulations Using Naturally-occurring Radionuclidesmentioning

confidence: 99%

“…For reasons discussed elsewhere [1,5), a closer match may be unlikely until consideration is given to the asymmetry of the sea-tank discharge, which is released around high water when the tide is flowing to the northwest, and to introducing a two-layer structure in the water column, following recent current meter measurements which indicated a de-coupling of flow around St Bees Head. Predicted sediment concentrations in the immediate vicinity of the discharge point were higher than measured values.…”

Section: Model Simulations Of the Plutonium Distributionmentioning

confidence: 99%

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Modelling the Behaviour of Long-Lived Radionuclides in the Irish Sea — Comparison of Model Predictions with Field Observations

Kershaw

Pentreath

Gurbutt

et al. 1988

Reliability of Radioactive Transfer Models

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A multi-compartmental box model of the Irish Sea has been developed to predict the distribution and radiological consequences of radionuclides discharged from the Sellafield reprocessing plant. The box structure was based on observations of radionuclide distributions in the sea bed and the water circulation was generated from extensive time-series data on 137Cs concentrations in seawater. Measurements of naturally-occurring nuclides provided both data on the extent and rate of these processes and a means to validate the model assumptions.The model structure is briefly outlined, comparisons are made between model predictions and field observation, and some of the difficulties in making such comparisons are discussed.

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“…234 Th/ 238 U = 1), a situation found in most of the deep water column of the ocean. But 234 Th is removed by scavenging, which explains why coastal waters are depleted in the isotope (Kershaw and Young, 1988;Kersten et al, 1998). The isotope is also removed from the surface waters of the ocean by particles sinking our of the surface layer, which process is the basis for the use of this tracer for the quantification of export production (Tsunogai and Minagawa, 1976;Coale and Bruland, 1985;Eppley, 1989).…”

Section: Introductionmentioning

confidence: 99%

Resuspension and particle transport in the benthic nepheloid layer in and near Fram Strait in relation to faunal abundances and 234Th depletion

Loeff

Meyer

Rudels

et al. 2002

Deep Sea Research Part I: Oceanographic Research Papers

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The West Spitsbergen Current, flowing northward through Fram Strait, causes a benthic nepheloid layer (BNL) on the western slope of the Yermak Plateau. This BNL is weaker on the eastern side of the Plateau and absent on the Greenland side of the Fram Strait where the East Greenland Current flows south. In this BNL we find throughout a depletion of 234 Th relative to its parent 238 U, and we use this to study the particle dynamics in the BNL. The export flux from the ice-covered surface ocean and from a young bloom found in the ice-free waters off NE Greenland is shown to be negligible, allowing us to explain the 234 Th depletion by interaction with the sediment alone. The depletion, balanced by a similar excess in the surface layer of the sediment, implies the existence of a settlingresuspension loop with an average particle residence time of 1-2 months.The asymmetry with a stronger resuspension loop on the western (80-120 mg m ) is reflected in the numbers of species and individuals of suspension feeders in box core samples, and in epifauna abundance as has been estimated from video observations. The suspension feeders thus contribute to deposit the particles that are advected from more productive ice-free regions. This explanation is in agreement with the eastwest asymmetry in the input of organic material to the sediments of the Yermak Plateau, which has been concluded by Soltwedel et al. (2000) from the distribution of pigments, bacterial activity and meiofauna abundances, observed in a concurrent study at the same stations. On the West Spitsbergen shelf, a very intensive BNL was monitored over one month with a moored filtration system. A part of the sustained high suspended load may be advected over long distances. This study gives an example how the tracer 234 Th can help to determine to what extent suspended particles are in continuous exchange with the seafloor, and where biological mediation and chemical modification can be expected.

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Scavenging of 234Th in the Eastern Irish Sea

Cited by 49 publications

References 28 publications

Determination of U, Pu and Am isotopes in Irish Sea sediment by a combination of AMS and radiometric methods

Determination of U, Pu and Am isotopes in Irish Sea sediment by a combination of AMS and radiometric methods

Modelling the Behaviour of Long-Lived Radionuclides in the Irish Sea — Comparison of Model Predictions with Field Observations

Resuspension and particle transport in the benthic nepheloid layer in and near Fram Strait in relation to faunal abundances and 234Th depletion

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