Vindedahl, Amanda2017-03-142017-03-142015-12https://hdl.handle.net/11299/185118University of Minnesota Ph.D. dissertation.December 2015. Major: Chemistry. Advisors: Lee Penn, William Arnold. 1 computer file (PDF); xvi, 184 pages.Natural organic matter can alter both the reactivity and aggregation state of iron oxide nanoparticles. In this work, we monitor both reactivity, via monitoring the rate of 4-chloronitrobenzene reductive degradation, and aggregation state, via characterization using dynamic light scattering and cryogenic transmission electron microscopy, of goethite nanoparticles with changing organic carbon concentration due to natural organic matter. At low concentration, nanoparticle aggregation is enhanced and at high concentration, aggregation is inhibited. Further, at high organic carbon concentration, the reactivity of goethite dramatically decreases, suggesting that natural organic matter blocks goethite reactive surface sites.enThesis or Dissertation