Effects of SO2 on NH4NO3 Photolysis: The Role of Reducibility and Acidic Products

Qing Cao; Biwu Chu; Peng Zhang; Qingxin Ma; Jinzhu Ma; Yuan Liu; Jun Liu; Yaqi Zhao; Hong Zhang; Yonghong Wang; Hong He

doi:10.1021/acs.est.3c01082

Effects of SO₂ on NH₄NO₃ Photolysis: The Role of Reducibility and Acidic Products

Environ Sci Technol. 2023 Jun 13;57(23):8671-8679. doi: 10.1021/acs.est.3c01082. Epub 2023 May 26.

Authors

Qing Cao^{1

2}, Biwu Chu^{1

2

3}, Peng Zhang^{1

2

3}, Qingxin Ma^{1

2

3}, Jinzhu Ma^{1

2

3}, Yuan Liu^{1

2}, Jun Liu¹, Yaqi Zhao^{1

2}, Hong Zhang^{1

4}, Yonghong Wang¹, Hong He^{1

2

3}

Affiliations

¹ State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
² University of Chinese Academy of Sciences, Beijing 100049, China.
³ Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
⁴ Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China.

PMID: 37235870
DOI: 10.1021/acs.est.3c01082

Abstract

Nitrate photolysis is a vital process in secondary NOx release into the atmosphere. The heterogeneous oxidation of SO₂ due to nitrate photolysis has been widely reported, while the influence of SO₂ on nitrate photolysis has rarely been investigated. In this study, the photolysis of nitrate on different substrates was investigated in the absence and presence of SO₂. In the photolysis of NH₄NO₃ on the membrane without mineral oxides, NO, NO₂, HONO, and NH₃ decreased by 17.1, 6.0, 12.6, and 57.1% due to the presence of SO₂, respectively. In the photolysis of NH₄NO₃ on the surface of mineral oxides, SO₂ also exhibited an inhibitory effect on the production of NOx, HONO, and NH₃ due to its reducibility and acidic products, while the increase in surface acidity due to the accumulation of abundant sulfate on TiO₂ and MgO promoted the release of HONO. On the photoactive oxide TiO₂, HSO₃^-, generated by the uptake of SO₂, could compete for holes with nitrate to block nitrate photolysis. This study highlights the interaction between the heterogeneous oxidation of SO₂ and nitrate photolysis and provides a new perspective on how SO₂ affects the photolysis of nitrate absorbed on the photoactive oxides.

Keywords: NH4NO3 photolysis; SO2; acidity; hole; mineral oxides; reducibility.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Minerals
Nitrates*
Oxides*
Photolysis

Substances

Nitrates
titanium dioxide
Oxides
Minerals