Atmospheric deposition over the Caribbean region: sea salt and Saharan
dust are sources of essential elements on the island of Guadeloupe
Abstract
Dust emitted from North Africa is transported over long distances and
has a strong impact on large areas over the North Tropical Atlantic
Ocean. Sea salt emitted by the sea surface is the second source of
essential elements transported in the atmosphere and plays a major role
in the cycles of alkaline-earth metals in the ecosystems of tropical
North Atlantic Islands. The total atmospheric deposition fluxes were
continuously sampled on a weekly basis in Guadeloupe, Lesser Antilles,
from March 2015 to August 2018 (41 months). Elemental deposition fluxes
including Al, Ca, K, Mg, Fe, Na, P, S, and Zn were measured for all
samples in order to provide the first long time series of atmospheric
elemental deposition fluxes over the Lesser Antilles region. It is shown
that: (i) the three sources of atmospheric deposits in
Guadeloupe for the presented elements are sea salt (for K, Ca, Mg, Na,
S), long-range transported Saharan dust (for Al, Ca, K, Fe), and
biogenic particles (for P and Zn); (ii) the average
deposition mass fluxes of sea salt and Saharan dust are 16.7
g.m-2.year-1 and 10.6
g.m-2.year-1, respectively,
without noticeable inter-annual variations; (iii) a pronounced
seasonality is found for the Saharan dust deposition, for which maximum
flux values are observed between June and July each year and 85% of the
annual deposition flux occurs between April and September;
(iv) the deposition flux of sea salt is strongly correlated
to local wind speed, without seasonality.