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Photochemical Aging of Beijing Urban PM2.5: HONO Production
journal contribution
posted on 2018-05-01, 00:00 authored by Fengxia Bao, Meng Li, Yue Zhang, Chuncheng Chen, Jincai ZhaoPhotochemical
aging represents an important transformation process
of aerosol particles in the atmosphere, which greatly influences the
physicochemical properties and the environmental impact of aerosols.
In this work, we find that Beijing urban PM2.5 aerosol
particles release substantial HONO, a significant precursor of •OH
radicals, into the gas phase during the photochemical aging process.
The generation of HONO exhibits a high correlation with the amount
of nitrate in PM2.5. The formation rate of HONO becomes
gradually decreased with the irradiation time, but can be restored
by introducing the acidic proton, indicative of the essential role
of the acidic proton in the HONO production. Other environmental factors
such as relative humidity, light intensity, and reaction temperature
also possess important influences on HONO production. The normalized
photolysis rate constant for HONO (JHNO3→HONO) is in the range of 1.22 × 10–5 s–1 ∼ 4.84 × 10–4 s–1, which is 1–3 orders of magnitude higher than the reported
photolysis rate constant of gaseous HNO3. The present study
implies that the photochemical aging of Beijing PM2.5 is
an important atmospheric HONO production source.