Iron is well known to change its oxidation state, where, for example, iron metal (Fe0) rapidly oxidizes to ?rust? in the form of Fe3+ oxides and hydroxides. The reverse may occur, where, for example, microbial processes may reduce Fe3+ oxide and hydroxide minerals to Fe2+ minerals or aqueous solutions. These changes, termed ?redox? transformations, profoundly affect the reactivity of iron oxide and hydroxide particles, which in turn may dramatically change the behavior of elements such as carbon, nitrogen, and phosphorus through changes in the absorption properties. Redox transformations affect the reactivity of iron oxide and hydroxide minerals, particularly in nanoparticles (defined as particles that have diameters in the nanometer range ? one-billionth of a meter). It is now recognized that nanoparticles are ubiquitous in the environment and represent one of the major means by which chemical reactions occur.
The work supported by this collaborative grant will bring together researchers and students from geology and engineering, applying a unique isotopic approach to understanding the reactivity of nanoparticulate iron oxides and hydroxides. By studying the spectral properties and relative abundance of the different isotopes of Fe (54Fe, 56Fe, and 57Fe), this work will provide a fingerprint for changes in chemical reactivity of the minerals goethite and magnetite, two very common iron minerals in the environment. The work will study the impact of particle size and chemical composition on particle reactivity. These results will in turn have direct application to studies of paleoclimate, environmental remediation, agricultural practices, and water quality.