Enhanced Nitrite Production from the Aqueous Photolysis of Nitrate in the Presence of Vanillic Acid and Implications for the Roles of Light-Absorbing Organics

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

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Author(s)

  • Yalin Wang
  • Dan Dan Huang
  • Wanyi Huang
  • Ben Liu
  • Qi Chen
  • Rujin Huang
  • Masao Gen
  • Xue Li
  • Tianwei Hao
  • Yunkai Tan
  • Ka In Hoi
  • Kai Meng Mok
  • Yong Jie Li

Related Research Unit(s)

Detail(s)

Original languageEnglish
Pages (from-to)15694–15704
Journal / PublicationEnvironmental Science and Technology
Volume55
Issue number23
Online published17 Nov 2021
Publication statusPublished - 7 Dec 2021

Abstract

A prominent source of hydroxyl radicals (OH), nitrous acid (HONO) plays a key role in tropospheric chemistry. Apart from direct emission, HONO (or its conjugate base nitrite, NO2-) can be formed secondarily in the atmosphere. Yet, how secondary HONO forms requires elucidation, especially for heterogeneous processes involving numerous organic compounds in atmospheric aerosols. We investigated nitrite production from aqueous photolysis of nitrate for a range of conditions (pH, organic compound, nitrate concentration, and cation). Upon adding small oxygenates such as ethanol, n-butanol, or formate as OH scavengers, the average intrinsic quantum yield of nitrite [φ(NO2-)] was 0.75 ± 0.15%. With near-UV-light-absorbing vanillic acid (VA), however, the effective φ(NO2-) was strongly pH-dependent, reaching 8.0 ± 2.1% at a pH of 8 and 1.5 ± 0.39% at a more atmospherically relevant pH of 5. Our results suggest that brown carbon (BrC) may greatly enhance the nitrite production from the aqueous nitrate photolysis through photosensitizing reactions, where the triplet excited state of BrC may generate solvated electrons, which reduce nitrate to NO2 for further conversion to nitrite. This photosensitization process by BrC chromophores during nitrate photolysis under mildly acidic conditions may partly explain the missing HONO in urban environments.

Research Area(s)

  • aqueous aerosol particles, brown carbon, effective quantum yield, HONO formation, nitrate photolysis, photosensitization

Citation Format(s)

Enhanced Nitrite Production from the Aqueous Photolysis of Nitrate in the Presence of Vanillic Acid and Implications for the Roles of Light-Absorbing Organics. / Wang, Yalin; Huang, Dan Dan; Huang, Wanyi et al.
In: Environmental Science and Technology, Vol. 55, No. 23, 07.12.2021, p. 15694–15704.

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