NIRT: Nanoparticle Fe as a Reactive Constituent in Air, Water, and Soil

Project Information

Principal Investigator	Michelle Scherer
Institution	University of Iowa
Project URL	View
Relevance to Implications	High
Class of Nanomaterial	Natural Nanomaterials
Impact Sector	Environment
Broad Research Categories	Generation, Dispersion, Transformation etc. Characterization
NNI identifier

Funding Information

Country	USA
Anticipated Total Funding	$1,400,000.00
Annual Funding	$466,666.67
Funding Source	NSF
Funding Mechanism	Extramural
Funding Sector	Government
Start Year	2005
Anticipated End Year	2008

Abstract/Summary

The goal of the proposed work is to understand the reactivity of iron (Fe) oxide nanoparticles in air, water, and soil environments. Fe oxide particles in the nanometer size range (< 100 nm) are ubiquitous in nature and their occurrence ranges from ultra-fine mineral dust in the atmosphere to nanocrystalline precipitates in the hydrosphere. Research into the reactivity of nanoparticle Fe oxides has been primarily aimed at understanding the bonding characteristics of atoms adsorbed at the surface. It is now recognized, however, that the behavior of Fe in the environment is strongly influenced by bacterially driven redox reactions, as well as the local chemistry and nature of mineral surfaces in rocks and soils, and by the presence of water. Therefore, detailed investigations of the redox chemistry of Fe oxide nanoparticles under conditions analogous to nature are critical to understanding the role of these tiny particles in the cycling of Fe in the environment. The proposed research will use advanced spectroscopic and analytical techniques, in conjunction with selective isotope labeling, to investigate redox processes occurring at the surface of Fe oxide nanoparticles in the presence of water. Of particular interest is the bacterially driven interaction between aqueous Fe, and mineral and cell surfaces, as well as redox reactions occurring during (i) Fe isotope exchange, (ii) transport of atmospheric Fe mineral dust, (iii) pollutant reduction, and (iv) microbial Fe oxidation. The experiments will use well characterized Fe oxide nanoparticles in batch and column reactors designed to mimic natural conditions by varying biogeochemical conditions, including microbe, mineral, and water composition, as well as flow conditions. Intellectual Merit. Despite the key role of Fe(III)-Fe(II) reactions in environmental and industrial applications, heterogeneous redox reactions occurring on nanoscale Fe oxides have been largely unexplored. This is due, in large part, to the analytical and spatial complexities of studying heterogeneous reactions of Fe in the presence of water. The proposed methodology overcomes this obstacle by using an innovative combination of 57Fe Mossbauer spectroscopy and high precision aqueous isotope ratio measurements to simultaneously measure isotope specific oxidation states and concentrations of Fe at the Fe oxide-water interface. This approach, in tandem with X-Ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM), will provide new information on how and where redox reactions occur on Fe oxide nanoparticles. The synergistic blend of expertise in Fe geochemistry, microbial Fe respiration, and atmospheric Fe mineral dust brought together with the proposed NIRT provides an unparalleled opportunity to study redox reactions involving Fe oxide nanoparticles during multiple components of the Fe biogeochemical cycle. Observing reactivity . particle size trends for four diverse, but related reactions provide a powerful mechanism to identify new phenomena that are unique to oxide particles within the nanometer size range. Broader Impacts. An innovative combination of spectroscopic and isotopic techniques, in addition to comprehensive mineral characterization methods, will result in an improved understanding of the behavior of Fe oxide nanoparticles in air, water, and soil. Our findings will directly impact newly developing theories on global carbon cycling (via microbial Fe respiration and atmospheric deposition of Fe in the ocean), as well as challenge our current understanding of important environmental and industrial processes including degradation of soil, sediment, and water quality, the evolution of earth.s geologic/magnetic record (via Fe isotope biosignatures), accelerated rates of corrosion, and condensation processes (which may have led to the origin of life on earth and biological activity on Mars). The exploratory, interdisciplinary nature of the proposed activity will provide excellent training for graduate, undergraduate, and high school students. Students, as well as participating scientists, will gain expertise in a variety of spectroscopic and microscopic tools through three hands-on Nanoscale Processes in the Environment Summer Workshops. During the workshop, students will collect, analyze, and interpret data from their own samples. Bimonthly .Fe Oxides in the Environment. student forums will also be established at each university. The overall goal is to expose students to new ideas and to provide a forum for the interdisciplinary discussion of students. ideas throughout the year. Finally, a new initiative, .Geology and Art., will be launched through the Geology Museum at U.W. Madison to educate the public about Fe nanoparticles. This NIRT addresses the NSE research and education theme .Nanoscale Processes in the Environment.