Bromocarbons in the tropical coastal and open ocean atmosphere during the 2009 Prime Expedition Scientific Cruise (PESC-09)
Atmospheric concentrations of very short-lived species (VSLS) bromocarbons, including CHBr<sub>3</sub>, CH<sub>2</sub>Br<sub>2</sub>, CHCl<sub>2</sub>Br, CHClBr<sub>2</sub>, and CH<sub>2</sub>BrCl, were measured in the Strait of...
| Main Authors: | , , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-08-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/14/8137/2014/acp-14-8137-2014.pdf |
| Summary: | Atmospheric concentrations of very short-lived species (VSLS) bromocarbons,
including CHBr<sub>3</sub>, CH<sub>2</sub>Br<sub>2</sub>, CHCl<sub>2</sub>Br, CHClBr<sub>2</sub>, and
CH<sub>2</sub>BrCl, were measured in the Strait of Malacca and the South China and
Sulu–Sulawesi seas during a two-month research cruise in June–July 2009.
The highest bromocarbon concentrations were found in the Strait of Malacca,
with smaller enhancements in coastal regions of northern Borneo. CHBr<sub>3</sub>
was the most abundant bromocarbon, ranging from 5.2 pmol mol<sup>−1</sup> in
the Strait of Malacca to 0.94 pmol mol<sup>−1</sup> over the open ocean.
Other bromocarbons showed lower concentrations, in the range of
0.8–1.3 pmol mol<sup>−1</sup> for CH<sub>2</sub>Br<sub>2</sub>,
0.1–0.5 pmol mol<sup>−1</sup> for CHCl<sub>2</sub>Br, and
0.1–0.4 pmol mol<sup>−1</sup> for CHClBr<sub>2</sub>. There was no significant
correlation between bromocarbons and in situ chlorophyll <i>a</i>, but positive
correlations with both MODIS and SeaWiFS satellite chlorophyll <i>a</i>. Together,
the short-lived bromocarbons contribute an average of
8.9 pmol mol<sup>−1</sup> (range 5.2–21.4 pmol mol<sup>−1</sup>) to
tropospheric bromine loading, which is similar to that found in previous
studies from global sampling networks (Montzka et al., 2011). Statistical
tests showed strong Spearman correlations between brominated compounds,
suggesting a common source. Log–log plots of CHBr<sub>3</sub>/CH<sub>2</sub>Br<sub>2</sub>
versus CHBr<sub>2</sub>Cl/CH<sub>2</sub>Br<sub>2</sub> show that both chemical reactions and
dilution into the background atmosphere contribute to the composition of
these halocarbons at each sampling point. We have used the correlation to
make a crude estimate of the regional emissions of CHBr<sub>3</sub> and to derive a
value of 32 Gg yr<sup>−1</sup> for the Southeast (SE) Asian region
(10° N–20° S, 90–150° E). Finally, we note that
satellite-derived chlorophyll <i>a</i> (chl <i>a</i>) products do not always agree well
with in situ measurements, particularly in coastal regions of high turbidity,
meaning that satellite chl <i>a</i> may not always be a good proxy for marine
productivity. |
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| ISSN: | 1680-7316 1680-7324 |