Intensity of Th and Pa scavenging partitioned by particle chemistry in the North Atlantic Ocean

The natural radionuclides 231 Pa and 230 Th are incorporated into the marine sediment record by scavenging, or adsorption to various particle types, via chemical reactions that are not fully understood. Because these isotopes have potential value in tracing several oceanographic processes, we invest...

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Bibliographic Details
Published in:Marine Chemistry
Main Authors: Hayes, Christopher T., Anderson, Robert F., Fleisher, Martin Q., Vivancos, Sebastian M., Lam, Phoebe J., Ohnemus, Daniel C., Huang, Kuo Fang, Robinson, Laura F., Lu, Yanbin, Cheng, Hai, Edwards, R. Lawrence, Moran, S. Bradley
Format: Article in Journal/Newspaper
Language:English
Published: 2015
Subjects:
Adsorption
GEOTRACES
Radioactive tracers
Suspended particulate matter
Trace elements
Mid-Atlantic Ridge
North Atlantic
Online Access:https://hdl.handle.net/1983/ecec92cd-7b88-43e5-aacf-95ac56c9dfcc
https://research-information.bris.ac.uk/en/publications/ecec92cd-7b88-43e5-aacf-95ac56c9dfcc
https://doi.org/10.1016/j.marchem.2015.01.006
http://www.scopus.com/inward/record.url?scp=84922782845&partnerID=8YFLogxK
Description
Summary:The natural radionuclides 231 Pa and 230 Th are incorporated into the marine sediment record by scavenging, or adsorption to various particle types, via chemical reactions that are not fully understood. Because these isotopes have potential value in tracing several oceanographic processes, we investigate the nature of scavenging using trans-Atlantic measurements of dissolved (<0.45μm) and particulate (0.8-51μm) 231 Pa and 230 Th, together with major particle composition. We find widespread impact of intense scavenging by authigenic Fe/Mn (hydr)oxides, in the form of hydrothermal particles emanating from the Mid-Atlantic ridge and particles resuspended from reducing conditions near the seafloor off the coast of West Africa. Biogenic opal was not found to be a significant scavenging phase for either element in this sample set, essentially because of its low abundance and small dynamic range at the studied sites. Distribution coefficients in shallow (<200m) depths are anomalously low which suggests either the unexpected result of a low scavenging intensity for organic matter or that, in water masses containing abundant organic-rich particles, a greater percentage of radionuclides exist in the colloidal or complexed phase. In addition to particle concentration, the oceanic distribution of particle types likely plays a significant role in the ultimate distribution of sedimentary 230 Th and 231 Pa.

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