The Influence of Hydrothermal Plumes on the Distribution of Anthropogenic Radionuclides Between the Particulate and Dissolved Phases: Results from U.S. Geotraces Equatorial Pacific Zonal Transect GP16

Abstract:

Here we present and discuss the results from the analysis of samples from selected stations collected on the US GEOTRACES Equatorial Pacific Zonal Transect (GP16) completed in 2013. The section, between Peru and Tahiti, encompasses a range of processes that influence the supply, removal, and internal cycling of trace metals and offers the opportunity to gain a better understanding of the drivers of the transport and fate of contaminants in the ocean. The capability to analyze water and filtered particulate samples in the quantities available, allows us to determine the partitioning of selected radionuclides among dissolved and particulate forms (Kd) and estimate Pu-particulate fluxes.

The overarching objective of our work is to determine the concentrations of several anthropogenic radionuclides, including ²³⁹Pu, ²⁴⁰Pu, ²³⁷Np, and ¹³⁷Cs with sufficient resolution to define their basin-wide distributions in the Pacific Ocean. Data collected in the East Pacific Rise hydrothermal plume allows a discussion on the partitioning behavior of plutonium and neptunium.