Combined effects of boundary layer dynamics and atmospheric chemistry on aerosol composition during new particle formation periods
<p>Characterizing aerosol chemical composition in response to meteorological changes and atmospheric chemistry is important to gain insights into new particle formation mechanisms. A BAECC (Biogenic Aerosols – Effects on Clouds and Climate) campaign was conducted during the spring 2014 at the...
Main Authors: | , , , , , , , , , , , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2018-12-01
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Series: | Atmospheric Chemistry and Physics |
Online Access: | https://www.atmos-chem-phys.net/18/17705/2018/acp-18-17705-2018.pdf |
Summary: | <p>Characterizing aerosol chemical composition in response to
meteorological changes and atmospheric chemistry is important to gain
insights into new particle formation mechanisms. A BAECC (Biogenic
Aerosols – Effects on Clouds and Climate) campaign was conducted during the
spring 2014 at the SMEAR II station (Station for Measuring Forest
Ecosystem–Aerosol Relations) in Finland. The particles were characterized by
a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). A
PBL (planetary boundary layer) dilution model was developed to assist
interpreting the measurement results. Right before nucleation events, the
mass concentrations of organic and sulfate aerosol species were both
decreased rapidly along with the growth of PBL heights. However, the mass
fraction of sulfate aerosol of the total aerosol mass was increased, in
contrast to a decrease for the organic mass fraction. Meanwhile, an increase
in LVOOA (low-volatility oxygenated organic aerosol) mass fraction of the
total organic mass was observed, in distinct comparison to a reduction of
SVOOA (semi-volatile OOA) mass fraction. Our results demonstrate that, at
the beginning of nucleation events, the observed sulfate aerosol mass was
mainly driven by vertical turbulent mixing of sulfate-rich aerosols between
the residual layer and the newly formed boundary layer, while the
condensation of sulfuric acid (SA) played a minor role in interpreting the
measured sulfate mass concentration. For the measured organic aerosols,
their temporal profiles were mainly driven by dilution from PBL development,
organic aerosol mixing in different boundary layers and/or partitioning of
organic vapors, but accurate measurements of organic vapor concentrations
and characterization on the spatial aerosol chemical composition are
required. In general, the observed aerosol particles by AMS are subjected to
joint effects of PBL dilution, atmospheric chemistry and aerosol mixing in
different boundary layers. During aerosol growth periods in the nighttime,
the mass concentrations of organic aerosols and organic nitrate aerosols
were both increased. The increase in SVOOA mass correlated well with the
calculated increase in condensed HOMs' (highly oxygenated organic molecules)
mass. To our knowledge, our results are the first atmospheric observations
showing a connection between increase in SVOOA and condensed HOMs during the
nighttime.</p> |
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ISSN: | 1680-7316 1680-7324 |