Aqueous-phase oxidation of organosulfur compounds initiated
by •OH radicals could be an important transformation
pathway
and can play a significant role in the atmospheric abundance and fate
of these compounds. Here, we measured the temperature-dependent kinetics
of •OH reactions with five C1 and C2 organosulfur compounds (two alkyl sulfates, methyl sulfate
(MS) and ethyl sulfate (ES), and three sulfonates, methanesulfonate
(MSA), hydroxymethanesulfonate (HMS), and 2-hydroxyethylsulfonate
(HES)) in aqueous phase using laser photolysis-long path absorption
(LP-LPA) and competition kinetics methods. The rate constants ranged
from 106 to 108 L mol–1 s–1 and exhibited a clear positive temperature (T) dependence over a temperature range of 278 to 318 K.
Furthermore, the two sulfur-containing groups, sulfate (−OSO3
–) group for alkyl sulfates and sulfite
(−SO3
−) group for sulfonates,
exhibit strong deactivating effect on the kinetics. This could be
explained by the strong electron-withdrawing nature of the −OSO3
– and −SO3
– groups, which lowers the hydrogen abstraction rates during •OH oxidation. Overall, this study demonstrates that
the oxidation of small alkyl sulfates and sulfonates by •OH radical in aqueous phase is significantly modulated by the presence
of the sulfur functional groups. The deactivating effect of sulfur
functional groups sheds light on predicting the lifetimes of other
organosulfur compounds in the atmosphere.