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| Titel |
Trends in particle-phase liquid water during the Southern Oxidant and Aerosol Study |
| VerfasserIn |
T. K. V. Nguyen, M. D. Petters, S. R. Suda, H. Guo, R. J. Weber, A. G. Carlton |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 20 ; Nr. 14, no. 20 (2014-10-16), S.10911-10930 |
| Datensatznummer |
250119103
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| Publikation (Nr.) |
 copernicus.org/acp-14-10911-2014.pdf |
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| Zusammenfassung |
| We present in situ measurements of particle-phase liquid water. Measurements
were conducted from 3 June to 15 July 2013 during the Southern Oxidant and
Aerosol Study (SOAS) in the southeastern US. The region is photochemically
active, humid, dominated by biogenic emissions, impacted by anthropogenic
pollution, and known to contain high concentrations of organic aerosol mass.
Measurements characterized mobility number size distributions of ambient
atmospheric aerosols in three states: unperturbed, dry, and dry-humidified.
Unperturbed measurements describe the aerosol distribution at ambient
temperature and relative humidity. For the dry state, the sample was routed
through a cold trap upstream of the inlet then reheated, while for the
dry-humidified state the sample was rehumidified after drying. The total
volume of water and semi-volatile compounds lost during drying was
quantified by differencing dry and unperturbed volumes from the integrated
size spectra, while semi-volatile volumes lost during drying were quantified
differencing unperturbed and dry-humidified volumes. Results indicate that
particle-phase liquid water was always present. Throughout the SOAS
campaign, median water mass concentrations at the relative humidity (RH)
encountered in the instrument typically ranged from 1 to 5 μg m−3
but were as high as 73 μg m−3. On non-raining days,
morning time (06:00–09:00) median mass concentrations exceeded
15 μg m−3. Hygroscopic growth factors followed a diel cycle and exceed
2 from 07:00 to 09:00 local time. The hygroscopicity parameter kappa
ranged from 0.14 to 0.46 and hygroscopicity increased with increasing
particle size. An observed diel cycle in kappa is consistent with changes in
aerosol inorganic content and a dependency of the hygroscopicity parameter
on water content. Unperturbed and dry-humidified aerosol volumes did not
result in statistically discernible differences, demonstrating that drying
did not lead to large losses in dry particle volume. We anticipate that our
results will help improve the representation of aerosol water content and
aqueous-phase-mediated partitioning of atmospheric water-soluble gases in
photochemical models. |
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