RAPID: Anthropogenic radionuclides in the Atlantic Ocean 4 decades after GEOSECS

In this project, researchers at the Lamont-Dougherty Earth Observatory of Columbia University will obtain the total concentrations of the anthropogenic radionuclides 239Pu, 240Pu, 237Np, and 137Cs in selected full-depth profiles from the various Atlantic GEOTRACES cruises occurring in 2010 (US, Netherlands, and Germany). This will allow the broad brush characterization of these anthropogenic radionuclides some 37 years after GEOSECS. The isotopes of interest, in addition to being transient tracers, exhibit a range of Kd values (sediment water distribution coefficients, Pu > Np ,Cs), and geochemical behaviors as well as provide a means to resolve different sources of radioactive contamination. This will allow the team to address processes such as advection (new water mass tracers), sources and sinks (characteristic isotopic signatures), as well as processes related scavenging and particle dynamics across a range of contrasting regions. The planned US, German, and Dutch GEOTRACES cruises transect regions that represent a full suite of physical and biogeochemical processes that affect TEIs. By comparing radionuclide distributions, isotopic composition, inventories, and inventory ratios of particle reactive (Pu) to conservative (Cs and Np), we will learn first order information about rates of scavenging and transport of these nuclides that is complimentary to that gained through study of other TEIs by GEOTRACES.

Since GEOSECS, -- the first and only study to produce a view of the global oceanic distributions of plutonium and 137Cs -- methods have improved requiring less volume and providing not only better sensitivity but additional information (i.e., mass spectrometric techniques are capable of measuring the 240Pu/239Pu atom ratio; traditional alpha spectrometry is not). Where possible, the team will compare distributions measured in 2010 to those measured in 1972-1973 providing a ca. 40-year perspective on processes that control the fate and transport of these contaminants. In addition to providing updated baselines for Pu and 137Cs concentrations in the Atlantic, they will also provide information on 237Np as well as the 240Pu/239Pu isotopic composition, which have not been measured at this scale.

Broader Impacts: This project will be an international collaboration and will yield valuable environmental radionuclide data from a number of locations throughout the Atlantic that would not be obtained otherwise. An important problem related to both anthropogenic climate change and sustainability is societal heavy reliance on fossil fuels as the main source of energy. Although the solution will certainly be complex, an increase in the proportion of energy derived from nuclear power is likely. The information gained from this proposal will be useful in assessing the fate of nuclides that might be released as a result of increased reliance on nuclear power in the future.