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

Christopher T. Hayes, Robert F. Anderson, Martin Q. Fleisher, Sebastian M. Vivancos, Phoebe J. Lam, Daniel C. Ohnemus, Kuo Fang Huang, Laura F. Robinson, Yanbin Lu, Hai Cheng, R. Lawrence Edwards, S. Bradley Moran

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67 Scopus citations


The natural radionuclides 231Pa and 230Th 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) 231Pa and 230Th, 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 230Th and 231Pa.

Original languageEnglish (US)
Pages (from-to)49-60
Number of pages12
JournalMarine Chemistry
StatePublished - Mar 1 2015

Bibliographical note

Funding Information:
Cruise management for GA03 was funded by the U. S. National Science Foundation to W. Jenkins ( OCE-0926423 ), E. Boyle ( OCE-0926204 ), and G. Cutter ( OCE-0926092 ). Radionuclide studies were supported by the NSF ( OCE-0927064 to LDEO, OCE-0926860 to WHOI, OCE-0927757 to URI, and OCE-0927754 to UMN). Additional support came from the European Research Council ( 278705 ) to LFR and a Ford Foundation Predoctoral Fellowship to SMV. Particle studies were supported by the NSF OCE-0963026 to PJL. The crew of the R/V Knorr, the Ocean Data Facility team (Mary Johnson, Rob Palomares, Susan Becker, and Courtney Schatzman), and the science team samplers for Niskin bottles and in-situ pumps (Katharina Pahnke, Brett Longworth, Paul Morris, Kuanbo Zhou, Sylvain Rigaud and Stephanie Owens) are all acknowledged for their critical roles in the success of these cruises. Figs. 1, 3, 6 and S1 were created using Ocean Data View ( Schlitzer, 2014 ). Maureen Auro and Joanne Goudreau are thanked for sample preparation efforts. We thank three anonymous reviewers for critical and constructive reviews. This is LDEO contribution 7867.

Publisher Copyright:
© 2015 Elsevier B.V.


  • Adsorption
  • Radioactive tracers
  • Suspended particulate matter
  • Trace elements


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