| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | June 15, 2015 |
| Latest Amendment Date: | June 15, 2015 |
| Award Number: | 1451508 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Enriqueta Barrera
EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | August 1, 2015 |
| End Date: | July 31, 2019 (Estimated) |
| Total Intended Award Amount: | $203,592.00 |
| Total Awarded Amount to Date: | $203,592.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
105 JESSUP HALL IOWA CITY IA US 52242-1316 (319)335-2123 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
2 Gilmore Hall Iowa City IA US 52242-1320 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): |
EnvE-Environmental Engineering, SURFACE EARTH PROCESS SECTION |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
Iron (Fe) is the fourth most abundant element on Earth and a critical nutrient for all life (from microorganisms to humans). Iron minerals are an important part of our lives: they are part of the soil beneath our feet; the rust on our cars; the hard drives in our computers; and the rocks on Earth and Mars. These tiny, often nanoscale, particles are responsible for most of the red, yellow, green, and black colors around us and they profoundly influence the quality of our water, air, and soil through biologically-driven redox cycling between oxidized ferric iron (Fe3+) and reduced ferrous iron (Fe2+). These Fe minerals trap much of the organic carbon (C) in soils and sediments and can also take the place of oxygen in anaerobic respiration, oxidizing and mineralizing organic matter to CO2 in anoxic soils and sediments. Increasing concerns about carbon driven climate change provides strong motivation to better understand the coupling between Fe and C processes that govern storage of carbon (C) in soils and sediments. The research findings from this work will benefit society by providing important insights into terrestrial response to climate change, as well as water quality preservation (such as arsenic release), and engineered water treatment systems. This project will provide authentic research experiences for individuals from groups underrepresented in the sciences at the upper high school (HS) and undergraduate (UG) levels. This will be accom-plished by involving long-term UG researchers in the project; providing HS junior and seniors from schools with historically low-college enrollment opportunities to participate in authentic summer research activities; and providing direct faculty-student instruction for HS and UG students as part of a ?Scale-Matters? workshop and Summer Soil Institute.
The overall goal of this research project is to understand the complex redox dynamics between Fe and organic C soils and sediments. In reducing environments, dissolved Fe2+ can catalyze Fe oxides to recrystallize into new mineral phases with similar or drastically different chemical properties. This process, Fe2+- catalyzed recrystallization, has been observed for pure Fe phases, but has yet to be explored as a pathway for mobilizing (or sequestering) organic C. Additionally, the presence of organic C is also likely to alter the recrystallization process with important implications for the Fe reactivity and isotope fractionation. The investigators will investigate how Fe2+- catalyzed recrystallization influences organic C and Fe mineral reactivity. To do this, the investigators will conduct a series of Fe isotope tracer experiments to quantify the extent of Fe2+- catalyzed recrystallization in model Fe-C assemblages synthesized from a range of Fe oxides and diversity of natural organic matter. Changes in Fe oxide susceptibility to microbial and chemical dissolution will be measured, along with Fe isotopic fractionation, and C availability following recrystallization of the Fe-C assemblages.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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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.
Iron (Fe) minerals make up about 5% of the Earth's crust and nearly all of the earth's core. These tiny, often nanoscale, particles profoundly influence the quality of our water, air, and soil through the biologically-driven redox cycling between ferric (Fe(III)) and ferrous iron (Fe(II)). They are also present in every computer, car, and most of the built structures we inhabit and the Fe(II)-Fe(III) redox couple is essential for most biological functions, such as metabolism, DNA synthesis, and oxygen transport. As part of previously funded NSF work, we developed an isotope tracking technique in which we could label the iron atoms in the particles and the water and track both the cycling between Fe(II) and Fe(III) and the mixing of iron atoms between the particles and water. We found that both cycling and mixing occurred which was hidden to traditional experimental approaches and could only be seen with the isotope labeling.
Our work here used this isotope tracking approach to explore whether mixing occurs even in the presence of organic carbon (C) which is commonly associated with these particles. Our results revealed that in certain soils and sediments these iron particle are both cycling between Fe(II) and Fe(III) and mixing with the surrounding water. The particles, which we once thought were stabilized by organic carbon, are much more dynamic and reactive then we once thought them to be. This hidden cycling and mixing in the presence of carbon raises the intriguing question of what happens to the carbon associated with the particles, as well as other elements, such as heavy metals (e.g., arsenic) that are often associated with these particles. We further found that both the amount and type of organic carbon plays an important role in whether the particles mix with the surrounding water and to help better understand how carbon influences the iron cycling and mixing, we measured and reported fundamental properties of the mineral particles in the presence of carbon.
Our isotope labeling experiments with iron minerals precipitated with organic carbon revealed that a wealth of hidden activity is occurring beneath the surface of iron minerals even when they are associated with organic carbon as they often are in soils and sediments. Most of this activity is invisible to most traditional experimental techniques. The implications of this hidden activity are yet unknown but have the potential to provide important insights into the terrestrial response to climate change, as well as water quality preservation (such as arsenic release), and engineered water treatment systems (e.g., river bank filtration).
A final, important outcome of this work is training several students in science and engineering students. The grant supported three graduate students and three undergraduate students making a significant contribution to the career development of scientists and engineers at various stages in their career. In addition, it has helped provide foundational science training for a high school student.
Last Modified: 07/26/2019
Modified by: Michelle M Scherer
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