Effects of SO<sub>2</sub> on optical properties of secondary organic aerosol generated from photooxidation of toluene under different relative humidity conditions
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Published:2020-04-17
Issue:7
Volume:20
Page:4477-4492
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ISSN:1680-7324
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Container-title:Atmospheric Chemistry and Physics
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language:en
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Short-container-title:Atmos. Chem. Phys.
Author:
Zhang WenyuORCID, Wang WeigangORCID, Li JunlingORCID, Peng Chao, Li KunORCID, Zhou Li, Shi Bo, Chen Yan, Liu Mingyuan, Ge MaofaORCID
Abstract
Abstract. Secondary organic aerosol (SOA) has great impacts on air
quality, climate change and human health. The composition and
physicochemical properties of SOA differ greatly because they form under
different atmospheric conditions and from various precursors as well as
differing oxidation. In this work, photooxidation experiments of toluene
were performed under four conditions (dry, dry with SO2, wet and wet
with SO2) to investigate the effect of SO2 under different
relative humidities on the composition and optical properties of SOA at
wavelengths of 375 and 532 nm. According to our results, the increase in
humidity enhances not only light absorption but also the scattering
property of the SOA. Oligomers formed through multiphase reactions might be
the reason for this phenomenon. Adding SO2 slightly lowers the real
part of the complex refractive index, RI(n), of toluene-derived SOA
(RI(n)dry,SO2<RI(n)dry, RI(n)wet,SO2<RI(n)wet), which might be a result of the partitioning of
low-oxidation-state products. The imaginary part of the complex refractive
index, RI(k), is enhanced under dry conditions with SO2 compared to that
of only dry conditions, which might be due to acid-catalyzed aldol
condensation reactions. Wet conditions with SO2 shows the combined
effect of SO2 and humidity. The extinction properties of
toluene-derived SOA under wet conditions with SO2 increased by
approximately 30 % compared to that of toluene-derived SOA formed under
dry conditions. Our results suggest that various atmospheric conditions will
affect the composition and optical proprieties of SOA, which has significant
implications for evaluating the impacts of SOA on the rapid formation of
regional haze, global radiative balance and climate change.
Funder
National Natural Science Foundation of China
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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