Heterogeneous SO 2 Oxidation in Sulfate Formation by Photolysis of Particulate Nitrate

Masao Gen, Ruifeng Zhang, Dan Dan Huang, Yongjie Li, Chak K. Chan

Research output: Contribution to journalArticlepeer-review

112 Citations (Scopus)

Abstract

Heterogeneous oxidation of sulfur dioxide (SO 2 ) is suggested to be one of the most important pathways for sulfate formation during extreme haze events in China, yet the exact mechanism remains highly uncertain. We propose a much less explored pathway for aqueous-phase SO 2 oxidation for the formation of particulate sulfate by NO 2 and OH radicals produced from photolysis of particulate nitrate. Reactive uptake experiments with SO 2 and ammonium nitrate particles under ultraviolet irradiation show measured SO 2 uptake coefficients of 10 -5 . Model calculations of sulfate production rates, comparing known mechanisms of oxidation by O 3 , NO 2 , H 2 O 2 , and transition metal ions, and the nitrate photolysis mechanism suggest that the nitrate photolysis pathway could contribute significantly to the overall sulfate production at pH 4-6. This study provides new insight into the current debate about sulfate production pathways under typical haze conditions in China.

Original languageEnglish
Pages (from-to)86-91
Number of pages6
JournalEnvironmental Science and Technology Letters
Volume6
Issue number2
DOIs
Publication statusPublished - 2019 Feb 12

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