Fog composition at Baengnyeong Island in the eastern Yellow Sea: detecting markers of aqueous atmospheric oxidations
Samples of fog water were collected at Baengnyeong Island (BYI) in the Yellow Sea during the summer of 2014. The most abundant chemical species in the fog water were NH<sub>4</sub><sup>+</sup> (mean of 2220 µM), NO<sub>3</sub><sup>−</sup> (1260 µM),...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-01-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/437/2016/acp-16-437-2016.pdf |
| Summary: | Samples of fog water were collected at Baengnyeong Island (BYI) in the
Yellow Sea during the summer of 2014. The most abundant chemical species in
the fog water were NH<sub>4</sub><sup>+</sup> (mean of 2220 µM),
NO<sub>3</sub><sup>−</sup> (1260 µM), SO<sub>4</sub><sup>−2</sup> (730 µM), and
Na<sup>+</sup> (551 µM), with substantial contributions from other
species consistent with marine and biomass burning influence on some dates. The pH of
the samples ranged between 3.48 and 5.00, with a mean of 3.94, intermediate
within pH values of fog/cloud water reported previously in Southeast Asia.
Back trajectories (72 h) showed that high relative humidity ( > 80 %) was
encountered upwind of the sampling site by all but one of the sampled air
masses, and that the fog composition at BYI can be impacted by several
different source regions, including the Sea of Japan, southeastern China,
northeastern China, and the East China Sea. Sulfur in the collected fog was
highly oxidized: low S(IV) concentrations were measured (mean of 2.36 µM) in contrast to SO<sub>4</sub><sup>−2</sup> and in contrast to fog/cloud
S(IV) concentrations from pollutant source regions; organosulfate species
were also observed and were most likely formed through aging of mainly
biogenic volatile organic compounds. Low-molecular-mass organic acids were
major contributors to total organic carbon (TOC; 36–69 %), comprising a
fraction of TOC at the upper end of that seen in fogs and clouds in other
polluted environments. Large contributions were observed from not only acetic
and formic acids but also oxalic, succinic, maleic, and other organic acids
that can be produced in aqueous atmospheric organic processing (AAOP)
reactions. These samples of East Asian fog water containing highly oxidized
components represent fog downwind of pollutant sources and can provide new
insight into the fate of regional emissions. In particular, these samples
demonstrate the result of extensive photochemical aging during multiday
transport, including oxidation within wet aerosols and fogs. |
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| ISSN: | 1680-7316 1680-7324 |