The Environmental chemical Sciences (ECS) program of the Division of Chemistry will support the collaborative research project of Prof. Michelle Scherer and Prof. Vicki Grassian of the University of Iowa, and Prof. Martin St. Clair of Coe College. The collaborating investigators and their students will study sorption dynamics of organic substances on iron oxide mineral surfaces. The study will make use of advanced spectroscopic methods and computational modeling methods to interrogate this complex and important environmental interface. Advanced surface spectroscopic methods will be used to characterize the molecular level details of the adsorbed surface complexes formed on nanoscale and microscale goethite and hematite particles. The study could significantly increase our understanding at the molecular level of redox processes on the environmentally ubiquitous iron oxide surfaces. Findings from this work will benefit society by providing insights into molecular scale reactions that are important in protecting the health of the Nation's water bodies. The study will provide excellent opportunities to graduate and undergraduate students at the University of Iowa and Coe College to work on a cutting edge research project in environmental chemical sciences.
Iron (Fe) oxides are ubiquitous. They are present in the soil beneath your feet, the rust on your car, the hard-drive in your computer, and the rocks on Earth and Mars. Essentially anywhere that iron is exposed to oxygen, Fe oxides form. These colorful red, yellow, green, and black minerals profoundly influence the quality of our water, air, and soil through the biologically-driven redox cycling between ferric (Fe3+) and ferrous iron (Fe2+). The mechanisms of Fe redox cycling, however, remains poorly understood because of the analytical challenge of distinguishing one Fe atom from another. We used a novel approach to overcome these challenges by linking molecular level characterization of surface speciation with isotope selective 57Fe-Mössbauer spectroscopy measurements of interfacial electron transfer. Results from our work show that there is a new pathway for cycling of Fe in the environment. A key outcome of this work is that this pathway is robust and can occur in the presence of many naturally occurring compounds in the environment, as well as with complex minerals. This pathway results in significantly more mixing of soil minerals with water than previously thought and has significant implication for other heavy metal pollutants, such as arsenic, as well as important elements, such as carbon and phosphorus, that tend to be heavily associated with soil minerals. A second important outcome is that carbon storage and sequestration may be influence by this new pathway for Fe cycling. Minerals found in soils are an important sink for carbon compounds, and our findings suggest that both carbon and trace elements in the minerals may be more mobile and less stable than we previously thought under certain conditions. Finally, our work demonstrates that transport of Fe-containing particles in the atmosphere effects how they behave in the ocean and that these effects need to be considered when estimating the input of Fe from dust particles in the ocean. Our findings have impact for a diverse set of disciplines including geology, material science, and energy production. The implications of our work for geology are significant in that the significant dissolution and cycling observed here suggest that Fe stable isotope signatures in ancient rocks will be not be particularly stable and caution will need to be used interpreting these signatures. For material science, our work suggests new pathways for mineral mining and industrial processing of critical ores. For energy production, we do not yet understand what is driving this extensive mixing and there is some possibility that these Fe oxides may be even more useful catalysts for energy production that we previously thought. As part of our project, we have trained nine students on critical thinking as applied to environmental chemistry. These students have been exposed to state of the art equipment in our labs as well as a national lab. The students have also learned how to communicate their science to the public through presentations, publications, and social media.
