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| Titel |
Chemical composition of rainwater at Maldives Climate Observatory at Hanimaadhoo (MCOH) |
| VerfasserIn |
R. Das, L. Granat, C. Leck, P. S. Praveen, H. Rodhe |
| 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 ; 11, no. 8 ; Nr. 11, no. 8 (2011-04-26), S.3743-3755 |
| Datensatznummer |
250009646
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| Publikation (Nr.) |
 copernicus.org/acp-11-3743-2011.pdf |
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| Zusammenfassung |
| Water-soluble inorganic components in rain deposited at the Maldives Climate
Observatory Hanimaadhoo (MCOH) were examined to determine seasonality and
possible source regions. The study, which is part of the Atmospheric Brown
Cloud (ABC) project, covers the period June 2005 to December 2007. Air mass
trajectories were used to separate the data into situations with transport of
air from India and adjacent parts of the Asian continent during the months
December and January (Indian group) and those with southerly flow from the
Indian Ocean during the summer monsoon season June to September (Marine
group). A third trajectory group was identified with transport from the
northern parts of the Arabian Sea and adjacent land areas during the months
March, April and October (Arabian Sea group). The concentrations of
nss-SO42−, NH4+ and NO3− were more than a factor of 4
higher in the Indian group than in the Marine group. The average
rainwater pH was significantly lower in the Indian group (4.7) than in the
Marine group (6.0). This shows a pronounced influence of continental
pollutants during December and January. The origin of the very high
concentration of nss-Ca2+ found in the Marine group – a factor of 7
higher than in the Indian group – is unclear. We discuss various
possibilities including long-range transport from the African or Australian
continents, local dust from nearby islands and calcareous plankton debris and
exopolymer gels emitted from the ocean surface. The occurrence of
NO3− and NH4+ in the Marine group suggests emissions from
the ocean surface. Part of the NO3− could also be associated with
lightning over the ocean. Despite the fact that the concentrations of
nss-SO42−, NO3−, and NH4+ were highest in the
Indian group the wet deposition was at least as big in the Marine group
reflecting the larger amount of rainfall during the monsoon season. The
annual wet deposition of NO3−, NH4+ and nss-SO42− at
MCOH is about a factor of three lower than observed at rural sites in India. |
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