Abstract:
Saharan dust outbreaks occur regularly and huge amounts of this mineral dust are able to cross the Atlantic where it is then washed out over the humid Amazon Basin and hence provides the ecosystem with nutrients. Interannual elevation of base metal deposition (K, Mg and Ca) in an Amazonian montane rain forest in Ecuador
was observed between 1998 and 2004 and strong evidence was shown that much of these base metals are deriving
from the Sahara during La Niña events, when more days than usually with dry spells are given over the Amazon
Basin. However, so far no direct proof for a Saharan dust input beyond the Amazon Basin has been obtained. Therefore, in this study data of trace elements, rare earth elements (REE) and Pb, Sr & Nd isotopes are presented from dust samples collected in a rain forest on the eastern Andean cordillera in south Ecuador in order to identify its provenance with a geochemical approach. In advance, periods of possible Saharan dust inputs were identified on basis of elevated base metal concentration in the rainfall samples, backward trajectories coming from the west and days with a dry spell over Brazil. The results of this study support the hypothesis that Saharan dust transport to the eastern Andean cordillera in south Ecuador occurs during la Niña events. During our study period Saharan dust inputs were identified with a high likelihood at least
on two days. However, there are indications that Saharan dust inputs also occurred on several more days. Thus, Sahara dust fertilizes the tropical montane rain forest on the eastern cordillera of the Andes.
