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| Titel |
Sahara dust, ocean spray, volcanoes, biomass burning: pathways of nutrients into Andean rainforests |
| VerfasserIn |
P. Fabian, R. Rollenbeck, N. Spichtinger, L. Brothers, G. Dominguez, M. Thiemens |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7340
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| Digitales Dokument |
URL |
| Erschienen |
In: 4th EGU Alexander von Humboldt Conference "The Andes: Challenge for Geosciences" ; Nr. 22 (2009-10-13), S.85-94 |
| Datensatznummer |
250014733
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| Publikation (Nr.) |
 copernicus.org/adgeo-22-85-2009.pdf |
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| Zusammenfassung |
Regular rain and fogwater sampling in the Podocarpus National Park, on the
humid eastern slopes of the Ecuadorian Andes, along an altitude profile
between 1960 and 3180 m, has been carried out since 2002. The samples,
accumulated over about 1-week intervals, were analysed for pH, conductivity
and major ions (K+, Na+, NH4+, Ca2+, Mg2+, Cl−, SO42−, NO3−, PO43−).
About 35% of the weekly samples had very low ion contents, with pH mostly
above 5 and conductivity below 10 μS/cm. 10-days back trajectories
(FLEXTRA) showed that respective air masses originated in pristine
continental areas, with little or no obvious pollution sources.
About 65%, however, were significantly loaded with cations and anions,
with pH as low as 3.5 to 4.0 and conductivity up to 50 μS/cm. The
corresponding back trajectories clearly showed that air masses had passed
over areas of intense biomass burning, active volcanoes, and the ocean, with
episodic Sahara and/or Namib desert dust interference.
Enhanced SO42− and NO3+ were identified, by combining
satellite-based fire pixel observations with back trajectories, as
predominantly resulting from biomass burning. Analyses of oxygen isotopes
16O, 17O, and 18O in nitrate show that nitrate in the samples
is indeed a product of atmospheric conversion of precursors. Some
SO42−, about 10% of the total input, could be identified to
originate from active volcanoes, whose plumes were encountered by about
10% of all trajectories.
Enhanced Na+, K+, and Cl− were found to originate from ocean
spray sources. They were associated with winds providing Atlantic air masses
to the receptor site within less than 5 days. Episodes of enhanced Ca2+
and Mg2+ were found to be associated with air masses from African
deserts. Satellite aerosol data confirm desert sources both on the Northern
(Sahara) as on the Southern Hemisphere (Namib), depending on the season. A
few significant PO43− peaks are related with air masses
originating from North African phosphate mining fields. |
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