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Research Spending & Results

Award Detail

Awardee:UNIVERSITY OF SOUTHERN MISSISSIPPI, THE
Doing Business As Name:University of Southern Mississippi
PD/PI:
  • Alan M Shiller
  • (228) 688-1178
  • alan.shiller@usm.edu
Award Date:02/01/2013
Estimated Total Award Amount: $ 199,565
Funds Obligated to Date: $ 199,565
  • FY 2013=$199,565
Start Date:01/15/2013
End Date:12/31/2016
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:Geotraces Pacific Section: Gallium, vanadium, and associated elements indicative of dust input and redox cycling
Federal Award ID Number:1261214
DUNS ID:623335775
Parent DUNS ID:623113990
Program:CHEMICAL OCEANOGRAPHY
Program Officer:
  • Henrietta Edmonds
  • (703) 292-8029
  • hedmonds@nsf.gov

Awardee Location

Street:2609 WEST 4TH ST
City:Hattiesburg
State:MS
ZIP:39401-5876
County:Hattiesburg
Country:US
Awardee Cong. District:04

Primary Place of Performance

Organization Name:University of Southern Mississippi
Street:
City:
State:MS
ZIP:39406-0001
County:Hattiesburg
Country:US
Cong. District:04

Abstract at Time of Award

During the 2013 GEOTRACES Eastern Pacific Zonal Section cruise, a scientist from the University of Southern Mississippi will determine the distributions of gallium (Ga) and vanadium (V), as well as V redox speciation. The planned cruise track is ideal for this effort because it will traverse various oceanic environments that influence the biogeochemistry of these elements namely, the Peru margin/upwelling zone and the associated oxygen minimum zone, gradients in atmospheric inputs and biological productivity from the Peru margin to Tahiti, and hydrothermal vents along the East Pacific Rise. Specific goals of the project include: (1) examine the discrepancy between surface water Ga and aluminum (Al) distributions and estimate dust inputs; (2) confirm the relationship observed in the North Pacific between the surface ocean Ga/Al ratio and the chlorophyll distribution; (3) compare the surface ocean manganese distribution with that of Ga, Al, and lead to differentiate between shelf and aerosol inputs; (4) determine if there is evidence of shelf V removal which contributes to the surface ocean V depletion; (5) test for hydrothermal influences on the V distribution downstream from the East Pacific Rise; and (6) compare V redox speciation with that of other elements including selenium, arsenic, and iodine as a means of examining the importance of water column reduction versus advective interactions with reducing coastal sediments. As such, the elements selected as the focus of this study, will provide information on dust input and redox cycling, especially when compared with other elements being determined by other cruise participants. Broader Impacts: Results from the study would be included into course materials for Oceanography and Marine Chemistry classes. One graduate student would be supported and trained as part of this project. Mentoring of high school student is also noted.

Publications Produced as a Result of this Research

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Ho, Peng and Lee, Jong-Mi and Heller, Maija I. and Lam, Phoebe J. and Shiller, Alan M. "The distribution of dissolved and particulate Mo and V along the U.S. GEOTRACES East Pacific Zonal Transect (GP16): The roles of oxides and biogenic particles in their distributions in the oxygen deficient zone and the hydrothermal plume" Marine Chemistry, v.201, 2018, p.. doi:10.1016/j.marchem.2017.12.003 Citation details  


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.

It is useful to determine the distributions of dissolved trace elements in the ocean because of the information they can provide on a wide variety of processes including biological productivity. Our project involved obtaining and analyzing selected trace elements in approximately 900 samples on an oceanographic cruise from the Peru margin to Tahiti. This section was designed to pass through a number of interesting and critical oceanic regimes including the highly productive Peru margin/upwelling zone, the associated Peru margin oxygen minimum and gradient in intermediate water oxygen concentrations, the gradient in biological productivity going from the Peru margin to Tahiti, hydrothermal sources/sinks along the East Pacific Rise, and a gradient in atmospheric inputs. While a wide variety of trace elements and isotopes were determined on cruise samples by various labs, our samples were analyzed for the elements barium (Ba), gallium (Ga), molybdenum (Mo), nickel (Ni), and vanadium (V). This suite includes elements that play a role in the cycling the critical nutrient, nitrogen (Mo, Ni, V); an element associated with input of materials to the surface ocean with dust (Ga), and an element whose incorporation into solid phases is related to biological productivity (Ba).

Key findings of our work can be summarized briefly. For Mo and V, ours are the first oceanic sections of these elements. Previous work suggested that these two elements showed little variability in their distributions, with nearly constant (i.e., conservative) concentrations of Mo and V showing only about a 5% decrease in shallow water compared to the deep ocean. While our work generally confirms these patterns, we also observed depletions of these elements associated with areas of intense nitrogen cycling and oxygen depletion off the Peru margin and with removal onto hydrothermal particles. We also observed changes in the Ni distribution correlated with indicators of intense nitrogen cycling. Thus, our work adds to the understanding of the role of these elements in the cycle of a key nutrient.

Our Ga section provides the first data on that element in the South Pacific. The section shows the expected comparatively low values in surface and intermediate waters due to low dust input. Deep water values are similar to deep water concentrations in the Atlantic, suggesting little influence of sediment sources on the Ga distribution. Comparisons with the geochemically-similar, but more reactive element aluminum (Al), suggest bottom input of Al but removal of that element in the mid-water column. Interestingly, near the Peru margin, we observe slightly increased dissolved Al but slightly lowed Ga, opposite of what we would expect based on their reactivities.

The Ba section is important because Ba incorporated into the sediments (as barite) is an indicator of productivity in the overlying waters. But the mechanisms linking barite formation, productivity, and the dissolved barium distribution are unclear. Our section can be interpreted as indicating barium removal in intermediate waters in the productive region off Peru and regeneration in deep waters in the same region.

This project also resulted in the training of one masters student and one doctoral student.


Last Modified: 04/05/2017
Modified by: Alan M Shiller

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