Recent advances in structure and reactivity of dissolved organic matter: radiation chemistry of non-isolated natural organic matter and selected model compounds.

The importance of natural organic matter (NOM) as a source of carbon in natural waters, as the source of reactive oxygen species, or for the complications its presence causes in treatment of natural waters, is undeniable. Recent studies have also pointed to the major photochemical role of triplet excited state of natural organic matter in the environmental fate of pharmaceutical and personal care products (PPCPs) in waters. However, the characterization of NOM is problematic due to its complex molecular structure. One approach to better understand NOM chemistry is the use of model compounds. As the condensation of a plant's phenolic compounds leads to humification and the formation of NOM, a structurally broad group of nine phenolic compounds were selected as model compounds for this study. With methods used in the discipline of radiation chemistry, the oxidative chemistry and transient spectra of these phenols were studied. In addition, the oxidative chemistry and transient spectra of a sample of NOM from the Black River, North Carolina, USA, was characterized. This natural water sample was used as received and represents the first studies of non-isolated NOM by pulsed radiolysis. The results of the transient spectra of the NOM revealed that the radical intermediates were very long lived. This phenomenon was not captured using the nine model compounds suggesting that more complex compounds are needed to further our understanding of the oxidation chemistry of NOM.