Aerosol hygroscopicity and its link to chemical composition in the coastal atmosphere of Mace Head: marine and continental air masses
<p>Chemical composition and hygroscopicity closure of marine aerosol in high time resolution has not been achieved yet due to the difficulty involved in measuring the refractory sea-salt concentration in near-real time. In this study, attempts were made to achieve closure for marine aerosol ba...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/20/3777/2020/acp-20-3777-2020.pdf |
| Summary: | <p>Chemical composition and hygroscopicity closure of marine
aerosol in high time resolution has not been achieved yet due to the
difficulty involved in measuring the refractory sea-salt concentration in near-real time.
In this study, attempts were made to achieve closure for marine aerosol
based on a humidified tandem differential mobility analyser (HTDMA) and a
high-resolution time-of-flight aerosol mass spectrometer (AMS) for
wintertime aerosol at Mace Head, Ireland. The aerosol hygroscopicity was
examined as a growth factor (GF) at 90 % relative humidity (RH). The
corresponding GFs of 35, 50, 75, 110 and 165 nm particles were
<span class="inline-formula">1.54±0.26</span>, <span class="inline-formula">1.60±0.29</span>, <span class="inline-formula">1.66±0.31</span>, <span class="inline-formula">1.72±0.29</span> and <span class="inline-formula">1.78±0.30</span> (mean <span class="inline-formula">±</span> standard deviation), respectively. Two contrasting air
masses (continental and marine) were selected to study the temporal
variation in hygroscopicity; the results demonstrated a clear diurnal
pattern in continental air masses, whereas no diurnal pattern was found in
marine air masses. In addition, wintertime aerosol was observed to be
largely externally mixed in both of the contrasting air masses. Concurrent high
time resolution PM<span class="inline-formula"><sub>1</sub></span> (particulate matter <span class="inline-formula"><i><</i>1</span> <span class="inline-formula">µ</span>m) chemical
composition data from combined AMS and MAAP measurements, comprising organic
matter, non-sea-salt sulfate, nitrate, ammonium, sea salt and black carbon
(BC), were used to predict aerosol hygroscopicity with the
Zdanovskii–Stokes–Robinson (ZSR) mixing rule. Overall, good agreement
(an <span class="inline-formula"><i>R</i><sup>2</sup></span> value of 0.824 and a slope of 1.02) was found between the growth
factor of 165 nm particles measured by the HTDMA (GF_HTDMA) and the growth factor derived from the AMS <span class="inline-formula">+</span> MAAP bulk
chemical composition (GF_AMS). Over
95 % of the estimated GF values exhibited less than a 10 % deviation for the
whole dataset, and this deviation was mostly attributed to the neglected
mixing state as a result of the bulk PM<span class="inline-formula"><sub>1</sub></span> composition.</p> |
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| ISSN: | 1680-7316 1680-7324 |