Recently a new class of pollutants, namely environmentally persistent free radicals (EPFRs), has emerged and been found at a number of Superfund sites. These Superfund site EPFRs have been found to associate with the clay/humin fraction and are of concern given the available toxicological data on similar combustion-generated EPFRs. However, unlike the combustion-generated EPFRs, these Superfund site EPFRs are generated under ambient environmental conditions and, in order to understand the mechanism behind their formation, our group has taken a systematic “bottom-up” approach. This presentation will focus on our work with Fe(III) and Cu(II)-loaded montmorillonite clay surrogates. The sorption of the parent compound (e.g., phenol) will be demonstrated by combining Fourier-transformed infrared (FT-IR) and X-ray diffraction (XRD) spectroscopies. The subsequent radical formation will be demonstrated by electron pair resonance (EPR), while the reduction of the Fe(III) or Cu(II) metal redox centers will be demonstrated by the X-ray absorption near edge structure (XANES). Based on the data provided by these techniques, a general mechanism for the formation of this type of EPFRs will be proposes. A range of environmental conditions, such as humidity, will be discussed in terms of their influence on the EPFR formation and stability. Finally, it will be shown that these Superfund soil-based EPFRs also have the potential to induce the formation of reactive oxygen species.<br/>

Developing a mechanistic understanding of environmentally persistent free radical redox formation in soils at ambient conditions

253rd National Meeting (2017)

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