Significantly Accelerated Hydroxyl Radical Generation by Fe(III)-Oxalate Photochemistry in Aerosol Droplets

Longqian Wang; Kejian Li; Yangyang Liu; Kedong Gong; Juan Liu; Jianpeng Ao; Qiuyue Ge; Wei Wang; Minbiao Ji; Liwu Zhang

doi:10.1021/acs.jpca.2c05919

Significantly Accelerated Hydroxyl Radical Generation by Fe(III)-Oxalate Photochemistry in Aerosol Droplets

J Phys Chem A. 2023 Jan 12;127(1):250-260. doi: 10.1021/acs.jpca.2c05919. Epub 2023 Jan 3.

Authors

Longqian Wang^{1

2}, Kejian Li^{1

2}, Yangyang Liu¹, Kedong Gong¹, Juan Liu¹, Jianpeng Ao³, Qiuyue Ge¹, Wei Wang¹, Minbiao Ji³, Liwu Zhang^{1

2}

Affiliations

¹ Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, Department of Environmental Science and Engineering, Fudan University, Shanghai200433, People's Republic of China.
² Shanghai Institute of Pollution Control and Ecological Security, Shanghai200092, People's Republic of China.
³ State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai200433, People's Republic of China.

PMID: 36595358
DOI: 10.1021/acs.jpca.2c05919

Abstract

Fe(III)-oxalate complexes are ubiquitous in atmospheric environments, which can release reactive oxygen species (ROS) such as H₂O₂, O^•2-, and OH^• under light irradiation. Although Fe(III)-oxalate photochemistry has been investigated extensively, the understanding of its involvement in authentic atmospheric environments such as aerosol droplets is far from enough, since the current available knowledge has mainly been obtained in bulk-phase studies. Here, we find that the production of OH^• by Fe(III)-oxalate in aerosol microdroplets is about 10-fold greater than that of its bulk-phase counterpart. In addition, in the presence of Fe(III)-oxalate complexes, the rate of photo-oxidation from SO₂ to sulfate in microdroplets was about 19-fold faster than that in the bulk phase. The availability of efficient reactants and mass transfer due to droplet effects made dominant contributions to the accelerated OH^• and SO₄^2- formation. This work highlights the necessary consideration of droplet effects in atmospheric laboratory studies and model simulations.