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Award Detail

Doing Business As Name:University of Minnesota-Twin Cities
  • R. Lawrence Edwards
  • (612) 626-0207
  • Hai Cheng
Award Date:07/09/2014
Estimated Total Award Amount: $ 454,947
Funds Obligated to Date: $ 454,947
  • FY 2016=$208,970
  • FY 2014=$44,829
  • FY 2015=$201,148
Start Date:01/01/2015
End Date:12/31/2018
Transaction Type:Grant
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: U.S. GEOTRACES Arctic Section: Thorium-230, Thorium-232, and Protactinium-231 tracers of trace element supply and removal.
Federal Award ID Number:1434886
DUNS ID:555917996
Parent DUNS ID:117178941
Program:Chemical Oceanography
Program Officer:
  • Henrietta Edmonds
  • (703) 292-7427

Awardee Location

Street:200 OAK ST SE
Awardee Cong. District:05

Primary Place of Performance

Organization Name:University of Minnesota-Twin Cities
Street:100 Union Street SE
Cong. District:05

Abstract at Time of Award

In support of the 2015 U.S.GEOTRACES Arctic expedition, this project will focus on the fate and distributions of naturally-occurring radioisotopes in the Arctic Ocean. Such information is useful for understanding why other chemical substances, both natural and man-made, occur where they do in the ocean. Like other national initiatives involved in the International GEOTRACES Program, the goals of this U.S. Arctic expedition are to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes (TEI) in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions. Working at sea alongside a multi-institutional team of ocean trace element experts, investigators on this project will define regions of unusually high rates of TEI removal, anticipated to be located near basin margins and near the sea floor. By combining their measurements of naturally-occurring thorium and protactinium with TEI data collected by other participating investigators, they expect to be able to translate these rates into information that can be applied to other TEIs. Like most other participating investigators, this group will include graduate students as part of the research team and will participate in a variety of public educational outreach activities for Alaskan communities. This study will undertake measurements of the dissolved and particulate concentrations of 230Th and 231Pa, two isotopes designated as key or critical to the success of the GEOTRACES program. Additionally the team will measure dissolved and particulate 232Th concentrations and analyze a limited number of aerosol samples, aerosol leachates, sea ice, melt pond water and surface sediments for these radionuclides. The work plan will be broken down into five tasks geared to: (1) determine the rates of boundary scavenging of 231Pa and 230Th associated with the particle-rich waters near the southern margin of the Canada Basin; (2) determine the rates of bottom scavenging of 231Pa and 230Th associated with nepheloid layers that are prevalent in the Arctic Ocean; (3) assess the contribution to scavenging in the Canada basin by MnO2-coated particles, formed during early diagenesis in organic-rich sediments surrounding the Arctic Ocean; (4) determine the rate of supply of lithogenic 232Th from margin sediments using information derived from 230Th; and (5) determine the rate of supply of lithogenic 232Th from sea ice, including the aerosols and ice-rafted sediments that they transport, by the combined study of 232Th and 230Th. The proposed work fulfills core scientific objectives defined in the U.S. GEOTRACES Arctic Implementation Plan.

Publications Produced as a Result of this Research

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Pavia, F., Anderson, R., Vivancos, S., Fleisher, M., Lam, P., Lu, Y.B., Cheng, H., Zhang, P., and Edwards, R.L. "Intense hydrothermal scavenging of 230Th and 231Pa in the deep Southeast Pacific." Marine Chemistry, v.201, 2018, p.212. 

Pavia, F.J., Anderson, R.F., Kipp, L.E.,Vivancos,S., Black, E.E., Fleisher, M.Q., Charette, M.A., Sanial, V., Moore, W., Hult, M., Lu, Y.B., Cheng, H., Zhang, P. and Edwards, R.L. "Timescales of Hydrothermal Scavenging in the South Pacific Ocean from 234Th, 230Th, and 228Th." EPSL, v.506, 2019, p.146. 

The GEOTRACES GROUP (E. Mawji, R. Schlitzer, E. Masferrer Dodas, C. Abadie, W. Abouchami,?R.F. Anderson, O. Baars, K. Bakker, M. Baskaran, N.R. Bates, K. Bluhm, A. Bowie, J. Bown, M. Boye, E.A. Boyle, P. Branellec, K.W. Bruland, M.A. Brzezinski, E. Buccia "The GEOTRACES intermediate data product" Marine Chemistry, v.177, 2015, p.1. j.marchem.2015.04.005 

Schlitzer, R., Anderson, R.F., Dodas, E.M., Lohan, M., Geibert, W., Tagliabue, A., Bowie, A., Jeandel, C., Maldonado, M.T., Landing, W., Cockwell, D., Abadie, C., Abouchami, W., Achterberg, E.P., Agather, A., Aguliar-Islas, A., 95, van Aken, H.M., Anderse "The GEOTRACES Intermediate Data Product 2017" Chemical Geology, v.493, 2018, p.210. 

Hayes, C.T., Anderson, R.F., Cheng, H., Conway, T.M., Edwards, R.L., Fleisher, M.Q., Ho, P., Huang, K.F., John, S.G., Landing, W.M., Little, S.H., Lu, Y.B., Morton, P.L., Moran S.B., Robinson, L.F., Shelley, R.U., Shiller, A.M., and Zheng X.Y. "Replacement times of a spectrum of elements in the North Atlantic based on thorium supply." Global Geochemical Cycles, v.32, 2018, p.1294. 

Hayes, C.T., Anderson, R.F., Fleisher, M.Q., Vivancos, S.M., Lam, P.J., Ohnemus, D.C.,Huang, K.F., Robinson, L.F., Lu, Y.B., Cheng, H., Edwards, R.L. and Moran, S.B. "Intensity of Th and Pa scavenging partitioned by particle chemistry in the North Atlantic Ocean." Marine Chem., v.70, 2015, p.49. 

Pavia, F.J., Anderson, R.R., Lam, P.J., Cael, B.B., Vivancos, S.M., Fleisher, M.Q., Lu, Y.B., Zhang, Pu, Cheng, H., and Edwards, R.L. "Shallow particulate organic carbon regeneration in the South Pacific Ocean." PNAS, v., 2019, p.. 

Valk, O., Rutgers van der Loeff, M.M., Geibert, W., Gdaniec, S., Rijkenberg, M.J.A., Moran, S.B., Lepore, K., Edwards, R.L., Lu, Y.B., and Puigcorbé, V. "Importance of hydrothermal vents in scavenging removal of Th-230 in the Nansen Basin." Geophysical Res. Lett., v.45, 2018, p.10539. 

Anderson, R., Cheng, H., Edwards, R.L., Fleisher, M., Hayes, C., Huang, K.F., Kadko, D., Lam, P., Landing, W., Lao, Y., Lu, Y.B., Measures, C., Moran, S.B., Morton, P., Ohnemus, D., and Shelley, R. "How well can we quantify dust deposition to the ocean" Phil. Trans. R. Soc. A, v.374, 2016, p.20150285. doi: 

Anderson, R.F., Cheng, H., Edwards, R.L., Fleisher, M.Q., Hayes, C.T. Huang, K.F., Kadko, D., Lam, P.J., Landing, W.M., Lao, Y., Lu, Y.B., Measures, C.I., Moran, S.B., Morton, P.L., Ohnemus, D.C., Robinson, L.F., and Shelley, R.U. "How well can we quantify dust deposition to the ocean?" Phil. Trans. R. Soc. A, v.374, 2016, p.20150285. 

Lerner, P., Lam, P.J. Marchal, O. Anderson, R.F., Buesseler, K., Charette, M., Edwards, R.L., Hayes, C.T. Huang, K.F., Lu, Y.B., and Robinson, L.F. "Testing Models of Thorium and Particle cycling in the Ocean using data from station GT11-22 of the U.S. GEOTRACES North Atlantic Section." Deep-Sea Research Part I, v.113, 2016, p.57. doi:doi:10.1016/j.dsr.2016.03.008 

Project Outcomes Report


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 major initiative to study the chemistry of the world's oceans as a means of understanding how the oceans work.  This project focused on the Arctic Ocean and on understanding the processes that affect the concentrations of exceedingly rare forms of the elements thorium and protactinium.  The particular forms of these elements have the unique characteristic that they are produced everywhere within the ocean at the same rate (from trace amounts of uranium naturally present throughout the oceans). Therefore, by measuring the concentrations of these elements in ocean waters and the particles contained within ocean water, we are able to ascertain processes within the ocean, which remove elements or redistribute elements within the ocean. 

In order to understand these processes, we analyzed hundreds of samples of Arctic Ocean water and of particles filtered from Arctic Ocean water.  We collected these samples at different sites around the Arctic and at different depths.  Indeed, not only did we analyze these many samples, but we developed new techniques to analyze different sized particles filtered from seawater.

With this data in hand, we proceeded to assess the processes that resulted in the pattern of concentrations that we observed.  We were able to assess processes such as the removal of trace metals near submarine hot springs and near the portions of the ocean close to the continents.  The former is important as it relates to the cycling of iron in the oceans and the latter is important as it relates to the cycling of carbon in the oceans. Both are ultimately related to carbon dioxide in the atmosphere and to the climate of the earth.

Last Modified: 05/01/2019
Modified by: R. Lawrence Edwards

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