Skip directly to content

Minimize RSR Award Detail

Research Spending & Results

Award Detail

Awardee:WRIGHT STATE UNIVERSITY
Doing Business As Name:Wright State University
PD/PI:
  • Chad R Hammerschmidt
  • (937) 775-3457
  • chad.hammerschmidt@wright.edu
Award Date:11/08/2012
Estimated Total Award Amount: $ 179,081
Funds Obligated to Date: $ 179,081
  • FY 2013=$179,081
Start Date:03/01/2013
End Date:02/29/2016
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: GEOTRACES Pacific Section: Mercury Speciation Along a Zonal Section in the Eastern Tropical South Pacific
Federal Award ID Number:1232979
DUNS ID:047814256
Parent DUNS ID:047814256
Program:Chemical Oceanography
Program Officer:
  • Henrietta Edmonds
  • (703) 292-7427
  • hedmonds@nsf.gov

Awardee Location

Street:3640 Colonel Glenn Highway
City:Dayton
State:OH
ZIP:45435-0001
County:Dayton
Country:US
Awardee Cong. District:10

Primary Place of Performance

Organization Name:Wright State University
Street:
City:
State:OH
ZIP:45435-0001
County:Dayton
Country:US
Cong. District:10

Abstract at Time of Award

Scientists from Wright State University and Woods Hole Oceanographic Institution will participate in the 2013 GEOTRACES cruise to the Eastern Tropical South Pacific (ETSP). Seawater samples collected during this transect from Peru to Tahiti will be analyzed for total mercury (Hg), monomethylmercury (CH3Hg+), dimethylmercury ((CH3)2Hg), and elemental Hg (Hg0) to construct high-resolution vertical and horizontal sections. In addition to filtered seawater samples, the scientists will also analyze suspended particles for total Hg and CH3Hg+, as well as rain and aerosol samples for Hg species and dissolved and particulate thiols, such as cysteine and glutathione. The cruise track extends from the upwelling region off Peru, to an expansive oxygen minimum zone (OMZ), followed by the hydrothermal vent fields of the East Pacific Rise, and finally into the highly oligotrophic waters near Tahiti. These different oceanographic features will allow the researchers to determine their influence on the inputs and cycling of Hg in the ocean. Specifically, they plan to assess whether (1) continental margins off Peru are a significant source of Hg, CH3Hg+, and (CH3)2Hg; (2) the OMZ sustains the highest levels of methylated Hg in the ocean; (3) hydrothermal systems are important sources of total and methylated Hg; and (4) the large gradient in productivity along this track impact the vertical distribution of this element, its bioavailability, and its speciation. In terms of broader impacts, this research may have societal benefits in helping to understand the source of methylmercury in the ocean, which bioaccumulates in fish and poses a hazard to those who eat seafood. In an effort to improve science education, the proponent from Wright State University and his graduate student plan to involve a class of 7th graders at Bellbrook Middle School in the Dayton area in their research experiences at sea via classroom visits, a blog, and interacting with them during the cruise. One graduate student and one undergraduate student from Wright State University would be supported and trained as part of this project.


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.

We participated in the U.S. GEOTRACES cruise to the eastern tropical South Pacific Ocean with the goal of studying the concentration and chemical form of mercury (Hg), a toxic metal present at low but concerning concentrations. Of particular importance on this cruise was the study of various chemical forms of Hg that are present in the ocean: total mercury (Hg) composed mostly of inorganic Hg2+, monomethylmercury (CH3Hg+), dimethylmercury ((CH3)2Hg), and elemental Hg (Hg0). It is important to study these forms of Hg separately because their fate and behavior in the ocean are different from one another. For example, Hg0 is a dissolved gas that builds up in surface ocean water enough to degas from the ocean and enter the atmosphere, representing a natural process of detoxification of Hg from the ocean. In contrast, CH3Hg+ is synthesized within the ocean and is the form of Hg that accumulates in seafood and poses a risk to human and environmental health. Thus, in order to understand the potential health risks of CH3Hg+ in seafood, we must gain an understanding of the chemical forms of Hg in seawater and how they interact with one another.

 

We measured concentrations of different chemical forms of Hg in filtered water, suspended particles, and rain and aerosols. These represent the sources and sinks of Hg to the ocean as well as the primary physical and chemical forms in the ocean. This particular cruise track, which extended west from the upwelling region of Peru, over the hydrothermal vent fields of the East Pacific Rise submarine mountain range and into low productivity waters near Tahiti, allowed us to test some fundamental questions regarding Hg cycling in the ocean including 1) how are methylated forms of Hg synthesized in the ocean and 2) are hydrothermal systems important sources of Hg to the ocean?

 

Some highlights from our findings include: 

  • Mercury exhibited nutrient-type vertical profiles: low concentrations at the surface that increase with depth. Such distributions are indicative of the bio-activity of Hg through its accumulation in plankton in the surface ocean (lowering the concentrations) and its release back into the water at depth as the plankton sink and decompose.  
  • The greatest concentrations of methylated Hg forms were observed near the seafloor on the Peruvian continental margin and in oxygen minimum zones in the water column. These are locations where we think there is net conversion of forms of Hg2+ into CH3Hg+ and (CH3)2Hg.
  • Based on other studies in the Pacific Ocean, we expected to see higher concentrations of Hg0 associated with locations where a lot of denitrification was occurring. Denitrification is the process in oxygen deficient waters that converts nitrate to N2 gas, leading to a loss of fixed nitrogen (nutrient N) from an aquatic system. In oceanographic terms, evidence for denitrification is often demonstrated with the N* metric, with negative N* values indicative of denitrification. During the cruise, we saw some weak evidence for a coupling of production of Hg0 from Hg2+ when N* was negative, but not as strongly as we had hypothesized. The source of Hg0 in “dark” waters, away from sunlight, is still therefore a mystery.
  • Although there is evidence that hydrothermal fluids from the East Pacific Rise can contain greatly increased concentrations of Hg, we saw no evidence of increased levels of Hg in the hydrothermal plume extending away from the East Pacific Rise. This is similar to what we observed at a hydrothermally active site at the Mid-Atlantic Ridge, and suggests that vents do not contribute a substa...

For specific questions or comments about this information including the NSF Project Outcomes Report, contact us.