Significant contribution of organics to aerosol liquid water content in winter in Beijing, China
<p>The aerosol liquid water (ALW) content (ALWC), an important component of atmospheric particles, has a significant effect on atmospheric optical properties, visibility and multiphase chemical reactions. In this study, ALWC is determined from aerosol hygroscopic growth factor (GF) and particl...
Main Authors: | , , , , , , , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2020-01-01
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Series: | Atmospheric Chemistry and Physics |
Online Access: | https://www.atmos-chem-phys.net/20/901/2020/acp-20-901-2020.pdf |
Summary: | <p>The aerosol liquid water (ALW) content (ALWC), an important component of atmospheric particles, has a significant effect on atmospheric optical
properties, visibility and multiphase chemical reactions. In this study,
ALWC is determined from aerosol hygroscopic growth factor (GF) and particle
number size distribution (PNSD) measurements and is also simulated by ISORROPIA II, a thermodynamic equilibrium model, with measured aerosol chemical composition
data taken at an urban site in Beijing from 8 November to 15 December 2017. Rich
measurements made during the experiment concerning virtually all aerosol
properties allow us not only to derive the ALWC but also to study the
contributions by various species for which little has been done in this
region. The simulated ALWC including the contribution of organics and the
calculated ALWC are highly correlated (coefficient of determination
<span class="inline-formula"><i>R</i><sup>2</sup>=0.92</span>). The ALWC contributed by organics (ALWC<span class="inline-formula"><sub>Org</sub></span>) accounts for <span class="inline-formula">30 <i>%</i>±22 <i>%</i></span> of the total ALWC during the sampling period. These results suggest a significant contribution of organics to ALWC, which is rather different from previous studies that showed negligible
contributions by organics. Our results also show that ALWC correlates well
with the mass concentrations of sulfate, nitrate, and secondary organic
aerosols (SOAs) (<span class="inline-formula"><i>R</i><sup>2</sup>=0.66</span>, 0.56 and 0.60, respectively). We further
noted that accumulation mode particles play a key role in determining ALWC,
dominating among all the aerosol modes. ALWC is an exponential function of
ambient relative humidity (RH), whose strong diurnal variation influence the
diurnal variation of ALWC. However, there is a 3 h lag between the
extremes of ALWC and RH values, due to the diurnal variations in PNSD and
aerosol chemical composition. Finally, a case study reveals that
ALWC<span class="inline-formula"><sub>Org</sub></span> plays an important role in the formation of secondary aerosols through multiphase reactions at the initial stage of a heavy-haze episode.</p> |
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ISSN: | 1680-7316 1680-7324 |