An introduction to the use of Polonium-210 as a tracer of sinking particles in the ocean

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.


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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.

Last modified May 20, 2020