Polonium-210

The method is very similar to that of Thorium-234. Polonium-210 (²¹⁰Po) is a naturally occurring radionuclide in the ocean, mainly formed from decay of its Lead-210 “parent” which is delivered to the oceans via atmospheric deposition, weathering and rivers. Like ²³⁴Th, lower levels of ²¹⁰Po than ²¹⁰Pb means more of the Polonium that is attached to the sinking particles is being removed. Then, downward ²¹⁰Po flux can be estimated. These same particles carry organic carbon and associated elements from the surface to the deep sea. If carbon and polonium are measured on the same particles, sinking flux of polonium can be converted into flux of carbon, which is a key parameter in considering the ocean’s role in the global carbon cycle and climate. The differences between ²¹⁰Po and ²³⁴Th are their biogeochemical properties - unlike thorium Polonium is assimilated by some phytoplankton and bacteria- and their radioactive half-lives – a longer half-life of ²¹⁰Po implies that water column sampling can be affected by previous export events.

Links to other resources

• ²¹⁰Po and size fractionated particle methods from EXPORTS
• ²³⁴Po “cookbook” style methods - general link
• EXPORTS ²¹⁰Po data

References

Rutgers, M.M van der Loeff and Geibert (2008) W. U- and Th-Series Nuclides as Tracers of Particle Dynamics, Scavenging and Biogeochemical Cycles in the Oceans. Radioactivity in the Environment. doi:10.1016/S1569-4860(07)00007-1

Ceballos-Romero. E. et al. (2016). Influence of bloom dynamics on Particle Export Efficiency in the North Atlantic: a comparative study of radioanalytical techniques and sediment traps. Marine Chemistry. doi:10.1016/j.marchem.2016.10.001.

Roca-Martí, M. et al. ( 2016) Carbon export fluxes and export efficiency in the central Arctic during the record sea‐ice minimum in 2012: a joint 234Th/238U and 210Po/210Pb study. Journal of Geophysical Research. Oceans doi:10.1002/2016JC011816.