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Environmental Processing of Short-Chain Fatty Alcohols Induced by Photosensitized Chemistry of Brown Carbons
journal contribution
posted on 2020-03-12, 09:43 authored by Bo You, Siyang Li, Narcisse T. Tsona, Jianlong Li, Li Xu, Zhaomin Yang, Shumin Cheng, Qingcai Chen, Christian George, Maofa Ge, Lin DuFatty
alcohols are known surfactants that are ubiquitous in the
environment. They affect the physical, chemical, and optical properties
of aerosols and air–water interfaces. However, little is known
about their photochemistry. Brown carbon (BrC), as a photosensitizer,
might initiate photochemical reactions of such nonphotoactive surfactants.
Here, BrC was obtained by evaporating mixtures of methylglyoxal with
ammonium sulfate or glycine (Gly). The photosensitization ability
of BrC was evidenced through its reaction with 1-octanol under UV
irradiation by means of attenuated total reflection–Fourier
transform infrared spectrometry, which is a surface-sensitive technique.
The condensed phase products were determined by gas chromatography–mass
spectrometry. We found that a series of functionalized and unsaturated
compounds were formed through photosensitized reaction, and more highly
oxygenated compounds appeared after a long illumination time. This
process contributes to the formation of reactive volatile and semi-volatile
organic species and could further trigger secondary chemistry. The
reaction is probably initiated by electronically excited BrC upon
exposure to UV irradiation. A possible mechanism for the photosensitized
degradation of fatty alcohols is proposed. We also observed that BrC
can be easily photobleached and hence has a limited effect on the
radiative forcing. However, BrC can play an important role in photochemistry
on aerosols and air–water interfaces.