Photochemical Interactions of Nitrate Photolysis and Photosensitization of BBOA: Enhanced HONO Production and the Formation of Nitrophenols
- 1Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
- 2Department of Civil and Environmental Engineering, Department of Ocean Science and Technology, and Centre for Regional Ocean, Faculty of Engineering, University of Macau, Macau 999078, China
Abstract
Renoxification of nitrate to reactive nitrogen species (RNS) can sustain atmospheric oxidant production. Because nitrate and light-absorbing brown carbon can coexist in biomass burning (BB) plumes, their photochemical interaction may alter RNS cycling. Furthermore, nitration of phenols in biomass burning organic aerosol (BBOA) can form nitrophenols, potentially increasing the warming effect of aged BBOA. Yet the mechanisms of renoxification and nitration in irradiated nitrate-BBOA mixtures remain poorly understood. We experimentally investigate these coupled processes over a wide range of fir-wood BBOA concentrations during aqueous nitrate photolysis (10 mM) under acidic conditions using H2SO4. At low BBOA concentration (TOCBBOA/NO3 – ≤ 0.0036 mg L–1/mg L–1), the steady-state production rate of HONO (P
ss_HONO ) increased as BBOA concentration increased, reaching a maximum enhancement factor of 1.8 driven primarily by triplet-mediated photosensitized reduction of NO2 to HONO. At higher BBOA concentration (TOCBBOA/NO3 – > 0.0036 mg L–1/mg L–1), P
ss_HONO progressively decreased and was nearly fully suppressed at TOCBBOA/NO3 – = 0.7 mg L–1/mg L–1. This inhibition is attributed to reactions of aqueous HNO2/NO2 with phenols, accompanied by formation of nitrophenols. These findings point to a potentially overlooked daytime HONO source and an atmospheric source of nitrophenols, a key class of BrC chromophores, via photochemical interactions between nitrate photolysis and photosensitization of BBOA.
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BibTeX
@article{zhang2026photochemical,
title = {{Photochemical Interactions of Nitrate Photolysis and Photosensitization of BBOA: Enhanced HONO Production and the Formation of Nitrophenols}},
author = {Ruifeng Zhang and Yong Jie Li and Chak K. Chan},
journal = {Environmental Science \& Technology},
year = {2026},
month = oct,
doi = {10.1021/acs.est.6c13970},
url = {https://doi.org/10.1021/acs.est.6c13970},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Photochemical Interactions of Nitrate Photolysis and Photosensitization of BBOA: Enhanced HONO Production and the Formation of Nitrophenols
AU - Ruifeng Zhang
AU - Yong Jie Li
AU - Chak K. Chan
PY - 2026
DA - 2026/10/19
JO - Environmental Science & Technology
DO - 10.1021/acs.est.6c13970
UR - https://doi.org/10.1021/acs.est.6c13970
AB - Renoxification of nitrate to reactive nitrogen species (RNS) can sustain atmospheric oxidant production. Because nitrate and light-absorbing brown carbon can coexist in biomass burning (BB) plumes, their photochemical interaction may alter RNS cycling. Furthermore, nitration of phenols in biomass burning organic aerosol (BBOA) can form nitrophenols, potentially increasing the warming effect of aged BBOA. Yet the mechanisms of renoxification and nitration in irradiated nitrate-BBOA mixtures remain poorly understood. We experimentally investigate these coupled processes over a wide range of fir-wood BBOA concentrations during aqueous nitrate photolysis (10 mM) under acidic conditions using H2SO4. At low BBOA concentration (TOCBBOA/NO3 – ≤ 0.0036 mg L–1/mg L–1), the steady-state production rate of HONO (P ss_HONO ) increased as BBOA concentration increased, reaching a maximum enhancement factor of 1.8 driven primarily by triplet-mediated photosensitized reduction of NO2 to HONO. At higher BBOA concentration (TOCBBOA/NO3 – > 0.0036 mg L–1/mg L–1), P ss_HONO progressively decreased and was nearly fully suppressed at TOCBBOA/NO3 – = 0.7 mg L–1/mg L–1. This inhibition is attributed to reactions of aqueous HNO2/NO2 with phenols, accompanied by formation of nitrophenols. These findings point to a potentially overlooked daytime HONO source and an atmospheric source of nitrophenols, a key class of BrC chromophores, via photochemical interactions between nitrate photolysis and photosensitization of BBOA.
SN - 0013-936X
SN - 1520-5851
ER -