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Physical and Chemical characterization of the
aerosol during the cruise Guieu/Losno/Bonnet/Blain
/Gaudichet

• 1)     Scientific objectives
• Determine the particles abundance of the area
• Determine the size distribution in order to
  attempt a IRON FLUX calculation.
• Determine the mineralogical composition.
• Determine some geochemical tracers (Al, Pb, )
  and elements of biogeochemical interest such as
  Fe and P.
• Quantify dissolved iron originating from these
  particles in the surface seawater

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les particules sahariennes (Barbades)
particules collectées au centre du Pacifique Nord
Particules issues de la pollution (MaceHead,
Irlande)
(Al 6000 ng.m-3)
(Al 15 ng.m-3)
Moyenne pendant Prosope Al 600 ng.m-3 avec un
échantillon 2000 ng.m-3
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Seasonal distributions of atmospheric Fe fluxes
to the global ocean. From model by Gao et al.,
2001. (GRL)
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Estimation of the Fe deposition to the South
Pacific Only from model (Gao et al., 2001, GRL)
Lowest predicted values in the South
pacific (along with Antarctic and Arctic)
This recent model used data from stations located
mainly on the western S Pacific ?No data in the
BIOSOPE area
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(2)     Methodology and measurements
The main goal is to chemically characterize the
aerosol in this very remote area

• HOW?
• Aerosol sampling during the transects and clean
  conditions. Contamination problems are crucial.
• measurements back in the lab on the particulate
  phase concentration of elements tracers of the
  lithogenic origin (Al, Si, Ti), pollution (Pb)
  and of element of biogeochemical interest for the
  project (Fe, P). ICP-AES, ICP-MS, XRF.
• Grain size distribution identification of the
  particles (clays, soot, glass, biogenic
  particles). Identification of the clays. Local or
  remote origin of the soot.

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The second objective is to conduct dissolution
experiments, in particular to quantify the
dissolved iron originating from this poor
atmosphere
HOW? -very simple protocol to avoid
contamination. Analysis back in France Fe, Si,
P, (Cu)
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DISSOLUTION EXPERIMENTS very simple protocol.
Has to be done inside the clean container
Aerosol (filter)

6 days
250 ml Filtered seawater/ unfiltered seawater
Acidification of the filtrate, storage. Analysis
? back in France
Filtration 0.2 µm
Clean / dark Teflon container
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(3)    Sampling

• Multi aerosol sampler
• Low volume samples 3 different filters will be
  performed at the same time, coupled with a
  Particles Counter. Sampling should be done
  strictly during clean periods.
• Water sampling for the dissolution experiment we
  will use the ultra-clean high flow rate sampling
  system samples from seasurface (no extra time
  needed from the regular sampling for iron
  measurement)

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