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Suspended particles has been the principal pollutant worsening
the air quality in Taiwan. The major constituents are carbon
contents, metal materials, water-soluble ions, and solidusts.
Among these materials, the water-soluble ions occupied a
significant proportion about 25 ~ 50% in the fine particles.
Nonetheless, there are few studies on the effects of the
temperature,relative humidity (RH), and light intensity of the
environment during the formation and evolution of these
particles. This work is focused on the generation and
progression of the ammonium nitrate particles. Nitrogen
dioxide, nitrous acid, and ammonium gas were injected into a
continuous stirred tank reactor (CSTR) with artificial
sunlight, controllable temperature, and RH. The reactants were
converted into aerosol particles through a gas-to-particle
process upon light incidence. The influences of the
environmental factors on aerosol formation were investigated in
this study. Based on the results, it was found that a good
linear relationship existed between NO2 photolysis rate
constant and light intensity. High temperature was beneficial
to promote the production rate of the ammonium nitrate
particles, whereas low temperature delayed their formations.
The modal diameter (190nm) of the aerosol size distribution at
35℃ was larger than that (160nm) at 25℃ . The environment
with low RH was harmful to the formation of the ammonium
nitrate particles, the aerosol production rate reached the
lowest under low temperature and RH. The increase of RH on
the number of fine particles was helpful, especially at high
value (74% in the study) the modal daimeter of the aerosol size
distribution approached around 170 ~ 180nm compared with 150 ~
160nm at low RH(10% in this work). Under the heterogeneous
condensation of the ammonium nitrate particles, the modal
diameter of the size distribution was increased from 150nm to
180nm which was probably due to the hygroscopic growth of the
aerosol particles.
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