References

ACPD

Atmospheric Chemistry and Physics Discussions

ACPD

1680-7375

Copernicus GmbH

Göttingen, Germany

10.5194/acpd-9-25023-2009

Chemical characterisation of iron in Dust and Biomass burning aerosols during AMMA-SOP0/DABEX: implication on iron solubility

Paris

¹ Desboeufs

K. V.

¹ Formenti

¹ Nava

² Chou

LISA, Universités Paris 12 et Paris 7, CNRS, Créteil, France

National Institute of Nuclear Physics, Florence, Italy

ETH, Institut für Atmosphäre und Klima, Zürich, Switzerland

25 11 2009

9 6 25023 25047

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Chemical composition and the soluble fraction (in MilliQ water) has been determined in aerosol samples collected during flights of AMMA-SOP0/DABEX campaign conducted in the West African Sahel during dry season (2006). Two types of samples are encountered in this period: dust particles (DUST) and biomass burning aerosol (BB). Chemical analysis and microscope observations show that iron (Fe) found in BB samples is mainly issued from dust particles externally mixed in the biomass burning layer. Chemical analyses of samples show that solubilities determined for Fe in samples of African dust were significantly lower than the solubilities in aerosols of biomass burning. Our data provide a first idea of the variability of iron dust solubility in the source region (0.1% and 3.4%). We found a relationship between iron solubility/clay content/source which partly confirms that the variability of iron solubility in this source region is related to the character and origin of the aerosols themselves. In the biomass burning samples, no relationship could be found between Fe solubility and the concentrations of acid species (SO42−,NO3− or oxalate) nor the content of carbon (TC, OC, BC) so we are unable to determine what are the processes involved in this increase of iron solubility. In terms of the supply of soluble Fe to oceanic ecosystems on a global scale, the observed higher solubility for Fe in biomass burning could imply an indirect source of Fe to marine ecosystem, but these aerosols are probably not significant because the Sahara is easily the dominant source of Fe to the Atlantic.

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