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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 17
Biogeosciences, 15, 5437-5453, 2018
https://doi.org/10.5194/bg-15-5437-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue: GEOVIDE, an international GEOTRACES study along the OVIDE...

Biogeosciences, 15, 5437-5453, 2018
https://doi.org/10.5194/bg-15-5437-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 14 Sep 2018

Research article | 14 Sep 2018

Distributions of total and size-fractionated particulate 210Po and 210Pb activities along the North Atlantic GEOTRACES GA01 transect: GEOVIDE cruise

Yi Tang1,2, Maxi Castrillejo3,4, Montserrat Roca-Martí3, Pere Masqué3,5, Nolwenn Lemaitre6, and Gillian Stewart2,1 Yi Tang et al.
  • 1Earth and Environmental Sciences, the Graduate Center, City University of New York, New York, USA
  • 2School of Earth and Environmental Sciences, Queens College, City University of New York, Flushing, USA
  • 3Institut de Ciència i Tecnologia Ambientals & Departament de Física, Universitat Autònoma de Barcelona, Bellaterra, 08193, Spain
  • 4Laboratory of Ion Beam Physics, ETH Zurich, Otto-Stern-Weg 5, Zürich, 8093, Switzerland
  • 5School of Science and Centre for Marine Ecosystems Research, Edith Cowan University, Joondalup, Western Australia, Australia
  • 6Department of Earth Sciences, Institute of Geochemistry and Petrology, ETH Zurich, Zürich, Switzerland

Abstract. Vertical distributions of total and particulate polonium-210 (210Po) and lead-210 (210Pb) activities in the water column were measured at 11 stations in the North Atlantic during the GEOTRACES GA01 transect: GEOVIDE cruise in May–June 2014. Total 210Po activity was on average 24% lower than 210Pb activity in the upper 100m, and it was closer to unity in the mesopelagic (100–1000m). The partitioning coefficients (Kd) along the transect suggest the preferential association of 210Po relative to 210Pb onto particles. The prominent role of small particles in sorption was confirmed by the observation that over 80% of the particulate radionuclide activity was on small particles. To account for the observed surface water 210Po210Pb disequilibria, particulate radionuclide activities and export of both small (1–53µm) and large ( > 53µm) particles must be considered. A comparison between the GEOVIDE total particulate 210Po210Pb activity ratios (ARs) and the ratios in previous studies revealed a distinct geographic distribution, with lower particulate ARs in the high-latitude North Atlantic (including this study) and Arctic in relation to all other samples. For the samples where apparent oxygen utilization (AOU) was calculated at the same depth and time as the 210Po210Pb AR (40 stations including this study), there was a two-phase correlation between the total particulate AR and AOU, likely reflecting the nature of the particles and demonstrating the forces of remineralization and radionuclide decay from particles as they age.

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We measured two natural radio-isotopes, 210Po and 210Pb, in the dissolved and particulate phase along the GEOVIDE cruise track to try to understand the cycling of these isotopes across a diverse combination of currents, basins, and conditions in the North Atlantic Ocean. Other groups collected data on many other trace elements and isotopes in order to map them as part of the GEOTRACES program. We found that Po and Pb activity was concentrated on small particles and varied within/between basins.
We measured two natural radio-isotopes, 210Po and 210Pb, in the dissolved and particulate phase...
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