Distributions of total and size-fractionated particulate <sup>210</sup>Po and <sup>210</sup>Pb activities along the North Atlantic GEOTRACES GA01 transect: GEOVIDE cruise
<p>Vertical distributions of total and particulate polonium-210 (<sup>210</sup>Po) and lead-210 (<sup>210</sup>Pb) 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....
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-09-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/15/5437/2018/bg-15-5437-2018.pdf |
| Summary: | <p>Vertical distributions of total and particulate polonium-210
(<sup>210</sup>Po) and lead-210 (<sup>210</sup>Pb) 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 <sup>210</sup>Po activity was on average 24 % lower than
<sup>210</sup>Pb activity in the upper 100 m, and it was closer to unity in
the mesopelagic (100–1000 m). The partitioning coefficients
(<i>K</i><sub>d</sub>) along the transect suggest the preferential association of
<sup>210</sup>Po relative to <sup>210</sup>Pb 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
<sup>210</sup>Po ∕ <sup>210</sup>Pb disequilibria, particulate radionuclide
activities and export of both small (1–53 µm) and large ( > 53 µm) particles must be considered. A comparison between the
GEOVIDE total particulate <sup>210</sup>Po ∕ <sup>210</sup>Pb 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
<sup>210</sup>Po ∕ <sup>210</sup>Pb 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.</p> |
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| ISSN: | 1726-4170 1726-4189 |