Abstract
Nowadays, the emission of nuisance odorants from Wastewater Treatment Plants (WWTPs) leads to persistent community complaints and localized air quality degradation. Predicting odorants' environmental impact requires a precise characterization of atmospheric lifetimes. This study determined the hydroxyl (•OH) radical reaction kinetics for 1,3,5-trimethylbenzene (TMB), Dimethyl trisulfide (DMTS), and 2-Isopropyl-3-methoxypyrazine (IPMP). Experiments were conducted in a laboratory-scale photochemical reactor, temperature-controlled at 298K via water bath circulation. •OH, were generated in situ through the photolysis of synthesized methyl nitrite (CH3ONO) within a 305-396 nm window. Using the relative rate method with toluene (TOL) as the reference compound (kref = 5.63x10-12 cm3 molecule-1 s-1), we derived bimolecular reaction rate constants of (k` = 6.97x10-12) for TMB, (k` = 6.39x10-12) for DMTS, and (k` = 3.78x10-12) for IPMP (units: cm3 molecule-1 s-1). Under a standard atmospheric concentration of [•OH] = 1x106 molecules/cm3, the calculated atmospheric half-lives (T1/2) were 27.1 hours (TMB), 30.1 hours (DMTS), and 50.9 hours (IPMP). These results indicate that IPMP exhibits the longest atmospheric lifetime among the studied compounds. The reported kinetic parameters contribute to a more accurate assessment of their atmospheric persistence. Overall, the determined kinetic parameters provide a quantitative basis for assessing the atmospheric degradation rates and persistence of the investigated odorants.
