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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 16, issue 19 | Copyright
Atmos. Chem. Phys., 16, 12829-12848, 2016
https://doi.org/10.5194/acp-16-12829-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 14 Oct 2016

Research article | 14 Oct 2016

Dry season aerosol iron solubility in tropical northern Australia

V. Holly L. Winton1,a, Ross Edwards1, Andrew R. Bowie2,3, Melita Keywood4, Alistair G. Williams5, Scott D. Chambers5, Paul W. Selleck4, Maximilien Desservettaz6, Marc D. Mallet7, and Clare Paton-Walsh6 V. Holly L. Winton et al.
  • 1Physics and Astronomy, Curtin University, Perth, Western Australia, Australia
  • 2Antarctic Climate and Ecosystems CRC, University of Tasmania, Hobart, Tasmania, Australia
  • 3Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
  • 4CSIRO, Ocean and Atmosphere, Aspendale, Victoria, Australia
  • 5Australian Nuclear Science and Technology Organisation, Sydney, New South Wales, Australia
  • 6Centre for Atmospheric Chemistry, University of Wollongong, Wollongong, New South Wales, Australia
  • 7Department of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland, Australia
  • anow at: British Antarctic Survey, Cambridge, UK

Abstract. Marine nitrogen fixation is co-limited by the supply of iron (Fe) and phosphorus in large regions of the global ocean. The deposition of soluble aerosol Fe can initiate nitrogen fixation and trigger toxic algal blooms in nitrate-poor tropical waters. We present dry season soluble Fe data from the Savannah Fires in the Early Dry Season (SAFIRED) campaign in northern Australia that reflects coincident dust and biomass burning sources of soluble aerosol Fe. The mean soluble and total aerosol Fe concentrations were 40 and 500ngm−3 respectively. Our results show that while biomass burning species may not be a direct source of soluble Fe, biomass burning may substantially enhance the solubility of mineral dust. We observed fractional Fe solubility up to 12% in mixed aerosols. Thus, Fe in dust may be more soluble in the tropics compared to higher latitudes due to higher concentrations of biomass-burning-derived reactive organic species in the atmosphere. In addition, biomass-burning-derived particles can act as a surface for aerosol Fe to bind during atmospheric transport and subsequently be released to the ocean upon deposition. As the aerosol loading is dominated by biomass burning emissions over the tropical waters in the dry season, additions of biomass-burning-derived soluble Fe could have harmful consequences for initiating nitrogen-fixing toxic algal blooms. Future research is required to quantify biomass-burning-derived particle sources of soluble Fe over tropical waters.

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The deposition of soluble aerosol iron (Fe) can initiate nitrogen fixation and trigger toxic algal blooms in nitrate-poor tropical waters. We present dry season soluble Fe data from northern Australia that reflect coincident dust and biomass burning sources of soluble Fe. Our results show that while biomass burning species are not a direct source of soluble Fe, biomass burning may substantially enhance the solubility of mineral dust with fractional Fe solubility up to 12 % in mixed aerosols.
The deposition of soluble aerosol iron (Fe) can initiate nitrogen fixation and trigger toxic...
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