Decay Kinetics and Absorption Changes of Methoxyphenols and Nitrophenols during Nitrate-Mediated Aqueous Photochemical Oxidation at 254 and 313 nm

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

6 Scopus Citations
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Author(s)

  • Yalin Wang
  • Wanyi Huang
  • Linhui Tian
  • Yuchen Wang
  • Fangbing Li
  • Dan Dan Huang
  • Ru-Jin Huang
  • Qi Chen
  • Xinlei Ge
  • Lin Du
  • Ying Ge Ma
  • Masao Gen
  • Ka In Hoi
  • Kai Meng Mok
  • Jian Z. Yu
  • Xue Li
  • Yong Jie Li

Related Research Unit(s)

Detail(s)

Original languageEnglish
Pages (from-to)1115–1125
Journal / PublicationACS Earth and Space Chemistry
Volume6
Issue number4
Online published28 Mar 2022
Publication statusPublished - 21 Apr 2022

Abstract

Brown carbon (BrC) absorbs radiation in the near-UV and visible ranges, affecting atmospheric photochemistry and radiative forcing. Our understanding on the photochemical transformation of BrC is still limited, especially when mixed with the abundant and photochemically labile inorganic salt, nitrate. Herein, we investigate the photochemical reactions of four BrC chromophores, including two methoxyphenols and two nitrophenols. Experiments were conducted in the absence and presence of different concentrations of H2O2 and nitrate with lights of 254 and 313 nm. The results show that the pseudo-first-order decay rate constants (k) of these four BrC compounds at 313 nm illumination were approximately 10 times lower than those at 254 nm, demonstrating longer lifetimes of these BrC chromophores under tropospherically relevant irradiation. Photo-enhancement in the visible range was observed in most experiments, with those under 313 nm illumination lasting longer, indicating the prolonged effects of nascent and transformed BrC chromophores on radiative forcing. Methoxyphenols had higher averaged k values than nitrophenols during direct photolysis with 254 or 313 nm lights, but the k values for nitrophenols under high-nitrate (or high-H2O2) conditions approached those of methoxyphenols. The photo-enhancement in the visible range for methoxyphenols in the presence of nitrate was substantially contributed by nitro products, while that for nitrophenols was mainly contributed by hydroxylated and/or dimerized products. Our results reveal the similarity and difference between the photolysis of methoxyphenols and nitrophenols, which may help better understand the aging of different types of BrC for better model representation of their effects on radiative forcing.

Research Area(s)

  • brown carbon, dimerization, hydroxylation, nitration, photolysis, visible absorption increase

Citation Format(s)

Decay Kinetics and Absorption Changes of Methoxyphenols and Nitrophenols during Nitrate-Mediated Aqueous Photochemical Oxidation at 254 and 313 nm. / Wang, Yalin; Huang, Wanyi; Tian, Linhui et al.
In: ACS Earth and Space Chemistry, Vol. 6, No. 4, 21.04.2022, p. 1115–1125.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review