Radiation-induced degradation products of 2-methyl isoborneol and geosmin: the role of different reactive species

Gamma radiolysis can serve as an effective method for the degradation of organic water pollutants, due to the production of reactive species, oxidative (OH•, OOH•, O2•-) or reductive (eaq-, H•). The application of scavengers enables the selective production of these species. Our aim was to explore the effects of the radiolytically produced reactive species, on commonly occuring water taste and odour compounds, 2-methyl isoborneol (MIB) and geosmin (GSM). Transformation products (TPs) were identified using liquid extraction followed by GC-MS/MS and confirmed with Linear Retention Indexes (LRI). The diversity and proposed structure of the TPs depend on the reactive species present in the solution. Structure elucidation of TPs revealed that reaction pathways are strongly dependant on the presence of individual reactive species. The oxidative degradation of MIB via OH• proceeds with the production of carbonyl- (camphor) and hydroxyl-containing TPs, a subsequent ring opening, arriving to linear structured products. Fewer TPs are produced upon the effect of OOH•, starting with a ring opening and addition of one hydroxyl group. The oxidative pathway of GSM via OH• occurs with an initial ring opening, formation of carboxyl-group and subsequent second ring opening. The reductive pathway is currently under study