GEOTRACES Pacific section: Dissolved and particulate concentrations of selected anthropogenic radionuclides along the U.S. GEOTRACES Peru-Tahiti zonal section

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The International GEOTACES Program is a global study of the marine biogeochemical cycles of trace elements and their isotopes (TEIs). In 2006, the GEOTRACES Science Plan defined the mission of GEOTRACES to be "To identify processes and quantify fluxes that control the distribution of key trace elements and isotopes in the ocean and to establish the sensitivity of these distributions to changing environmental conditions". To achieve this mission, the Science Plan further sets one of the primary goals to be the determination of the global ocean concentration and speciation of TEIs as well as the biological, chemical, and physical processes governing their distribution. Anthropogenic radionuclides (i.e., those associated with nuclear energy production and defence activities) are included in the Science Plan as "parameters of interest".In this project, a research team at the Lamont-Dougherty Earth Observatory of Columbia University will measure water column concentrations of 239Pu, 240Pu, 237Np, and 137Cs in dissolved and particulate phases along the 2013 US GEOTRACES Pacific zonal section from Peru to Tahiti. For much of the study region, these will be baseline vertical profiles of these radionuclides; that is, very few (if any) data on their distribution are currently available. These same anthropogenic radionuclides will also be measured in surface sediments at a few selected sites. Where possible, the team will compare the 2013 data to measurements made in 1972-1973, thus obtaining a four-decade perspective on processes controlling the distribution and fate of these substances.Broader Impacts: This project will feature international collaboration with other marine radiochemists. It will also include agressive educational outreach to undergraduate and high school students to advance public understanding of environmental radioactivity.