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| Titel |
Factors influencing the large-scale distribution of Hg° in the Mexico City area and over the North Pacific |
| VerfasserIn |
R. Talbot, H. Mao, E. Scheuer, J. Dibb, M. Avery, E. Browell, G. Sachse, S. Vay, D. Blake, G. Huey, H. Fuelberg |
| 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 ; 8, no. 7 ; Nr. 8, no. 7 (2008-04-11), S.2103-2114 |
| Datensatznummer |
250006038
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| Publikation (Nr.) |
 copernicus.org/acp-8-2103-2008.pdf |
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| Zusammenfassung |
| Gas-phase elemental mercury (Hg°) was measured aboard the NASA DC-8
aircraft during the Intercontinental Chemical Transport Experiment Phase B
(INTEX-B) campaign in spring 2006. Flights were conducted around Mexico City
and on two subsequent deployments over the North Pacific based out of
Honolulu, Hawaii and Anchorage, Alaska. Data obtained from 0.15–12 km
altitude showed that Hg° exhibited a relatively constant vertical
profile centered around 100 ppqv. Highly concentrated pollution plumes
emanating from the Mexico City urban agglomeration revealed that mixing
ratios of Hg° as large as 500 ppqv were related to combustion tracers
such as CO, but not SO2 which is presumably released locally from coal
burning, refineries, and volcanoes. Our analysis of Mexico City plumes
indicated that widespread multi-source urban/industrial emissions may have a
more important influence on Hg° than specific point sources. Over the
Pacific, correlations with CO, CO2, CH4, and C2Cl4 were
diffuse overall, but recognizable on flights out of Anchorage and Honolulu.
In distinct plumes originating from the Asian continent the Hg°- CO
relationship yielded an average value of ~0.56 ppqv/ppbv, in good
agreement with previous findings. A prominent feature of the INTEX-B dataset
was frequent total depletion of Hg° in the upper troposphere when
stratospherically influenced air was encountered. Ozone data obtained with
the differential absorption lidar (DIAL) showed that the stratospheric
impact on the tropospheric column was a common and pervasive feature on all
flights out of Honolulu and Anchorage. We propose that this is likely a
major factor driving large-scale seasonality in Hg° mixing ratios,
especially at mid-latitudes, and an important process that should be
incorporated into global chemical transport models. |
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