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Research Spending & Results

Award Detail

Awardee:WOODS HOLE OCEANOGRAPHIC INSTITUTION
Doing Business As Name:Woods Hole Oceanographic Institution
PD/PI:
  • Ken O Buesseler
  • (508) 289-2309
  • kbuesseler@whoi.edu
Co-PD(s)/co-PI(s):
  • Matthew A Charette
Award Date:11/08/2012
Estimated Total Award Amount: $ 1,100,000
Funds Obligated to Date: $ 1,100,000
  • FY 2014=$651,213
  • FY 2013=$448,787
Start Date:12/01/2012
End Date:05/31/2016
Transaction Type:Grant
Agency:NSF
Awarding Agency Code:4900
Funding Agency Code:4900
CFDA Number:47.050
Primary Program Source:040100 NSF RESEARCH & RELATED ACTIVIT
Award Title or Description:Collaborative Research:US GEOTRACES Pacific Zonal Transect: Rates of supply, removal and internal cycling of trace elements and isotopes
Federal Award ID Number:1232669
DUNS ID:001766682
Parent DUNS ID:001766682
Program:Chemical Oceanography
Program Officer:
  • Henrietta Edmonds
  • (703) 292-7427
  • hedmonds@nsf.gov

Awardee Location

Street:183 OYSTER POND ROAD
City:WOODS HOLE
State:MA
ZIP:02543-1041
County:Woods Hole
Country:US
Awardee Cong. District:09

Primary Place of Performance

Organization Name:Woods Hole Oceanographic Institution
Street:183 Oyster Pond Road
City:Woods Hole
State:MA
ZIP:02543-1501
County:Woods Hole
Country:US
Cong. District:09

Abstract at Time of Award

The goal of GEOTRACES is to identify processes and quantify fluxes that control the distribution of trace elements and isotopes (TEIs) in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions. While the distribution of numerous TEIs will be mapped by a large team of GEOTRACES PIs along this transect, their distribution cannot be properly interpreted without concurrent measurement of tracers capable of providing rates of internal TEI cycling processes and fluxes at boundaries and across interfaces. Naturally-occurring radioisotopes of the Uranium-Thorium series are well suited for studying the sources and sinks of TEIs on time and space scales necessary to interpret lateral and vertical TEI distributions. In this project, a research team from the Woods Hole Oceanographic Institution and the University of South Carolina at Columbia will carry out measurement of a suite of uranium/thorium series radionuclides on the US GEOTRACES cruise to the Eastern Tropical South Pacific (ETSP) Ocean. This radiotracer suite will include shorter-lived 234Th and 228Th as well as the radium quartet (224Ra, 223Ra, 228Ra, 226Ra), which together allow the quantification of rates of horizontal and vertical transport and mixing, as well as removal at ocean boundaries, surface export, and subsurface remineralization. Broader Impacts: The PIs have actively involved undergraduate and high school students in their prior NSF-funded projects, with two having won awards at ASLO meetings in recent years. The trend will continue with this effort, along with the inclusion of an international guest student who will work on analytical improvements for measuring particulate 228Th. In addition, two WHOI-MIT Joint Program students will be involved using this project as a major part of their PhD theses on Th and Ra isotopes. Contributions to the data management side of the results from these 6 isotopes is eagerly awaited by the modeling community, where there is a lack of multiple thorium isotope data sets on these basin scales for parameterization of the cycling of all particle reactive and biologically active TEIs.

Publications Produced as a Result of this Research

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Henderson, P.B., Morris, P.J., Moore, W.S., Charette, M.A. "Methodological advances for measuring low level radium isotopes in seawater." Journal of Radioanalytical and Nuclear Chemistry, v.296, 2013, p.357. doi:doi: 10.1007/s10967-012-2047-9 


Project Outcomes Report

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

This project is part of a larger program called “GEOTRACES” (http://www.geotraces.org), which seeks to identify processes that control the distribution of trace elements in the ocean.   The goal of this effort was to measure naturally occurring isotopes of radium and thorium.  By measuring their concentrations in the ocean, we can quantify rates of both horizontal (with radium) and vertical (with thorium) processes that impact trace element distributions in the ocean.  This is important, as while the distribution of numerous trace elements will be mapped by other GEOTRACES scientists, their distribution cannot be properly interpreted without concurrent measurement of tracers capable of providing rates of internal elemental cycling processes and fluxes at boundaries and across interfaces.

For radium, the idea is that radium is largely soluble with source at the sea floor and ocean margin sediments.  Its transport via largely horizontal physical processes will lead to a decrease in its concentration from the source.  Given the half-life of each of the four radium isotopes (days to >1,000 years), we can estimate time scales of horizontal mixing. 

Thorium isotopes in contrast are more particle-reactive, so found associated with marine particles that are both suspended and sinking.  Their sources are the dissolved uranium isotopes.  Any loss of thorium on sinking particles (a so called U/Th disequilibrium) can be used to quantify the flux of thorium on sinking particles.  Using ratios of thorium to other trace elements on the same particles, we can then determine the sinking flux of trace elements.

This particular GEOTRACES sampling took place between Peru and Tahiti in October/November 2013, resulting in the collection by this team of 1000’s of samples for the shorter-lived 234Th and 228Th as well as the radium “quartet” (224Ra, 223Ra, 228Ra, 226Ra).  The cruise track was selected to include gradients in productivity (higher near shore), changes due to an extensive oxygen minimum zone (OMZ) and impacts due to hydrothermal activity.  

 Our results have shown across these gradients, higher particle export near the margins and rapid remineralization (loss of sinking particles) just above the OMZ .  In addition, the distribution of 228Ra displays high activities in the first 300 m up to approximately 115°W, suggesting lateral advection, and close to the bottom due to the radium diffusion from deep sediments.  Radium isotopes are also being used to constrain the time scale of transport of the neutrally buoyant hydrothermal plume observed along the east Pacific Rise.  223Ra, 228Ra, and 226Ra are all elevated in the plume, while any hydrothermal signal of 224Ra is obscured by a large benthic source at this station. The ratio of 223Ra:226Ra has been used to estimate that the age of the plume at a station near the vents to be on the order of weeks, suggesting that the vent is likely 5-10 km away.  The radium isotopes will also help determine the age of the plume farther away from the ridge axis, which will be valuable in determining the transport rates of hydrothermally influenced trace elements in the deep Pacific ocean.

We note that this project supported three Ph.D. students, two from MIT-WHOI PhD program and one as a visiting student from France.   Several talks at conferences and workshops have been given, peer reviewed publications produced as well as one patent for new marine sampling system for collection of trace metal clean particles and dissolved components.  Finally all data are made available through the GEOTRACES program office and the Woods Hole BCO- Data Management Office.  

 


Last Modified: 08/29/2016
Modified by: Ken O Buesseler

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