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Preprints
https://doi.org/10.5194/acp-2020-437
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-2020-437
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  28 May 2020

28 May 2020

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A revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Distinct chemical and mineralogical composition of Icelandic dust compared to North African and Asian dust

Clarissa Baldo1, Paola Formenti2, Sophie Nowak3, Servanne Chevaillier2, Mathieu Cazaunau2, Edouard Pangui2, Claudia Di Biagio2, Jean-Francois Doussin2, Konstantin Ignatyev4, Pavla Dagsson Waldhauserova5,6, Olafur Arnalds5, A. Robert MacKenzie1, and Zongbo Shi1 Clarissa Baldo et al.
  • 1School of Geography Earth and Environmental Sciences, University of Birmingham, Birmingham, UK
  • 2LISA, UMR CNRS 7583, Université Paris-Est-Créteil, Université de Paris, Institut Pierre Simon Laplace (IPSL), Créteil, France
  • 3Plateforme RX UFR de chimie, Université de Paris, Paris, France
  • 4Diamond Light Source, Didcot, Oxfordshire, UK
  • 5Agricultural University of Iceland, Keldnaholt, Reykjavik, Iceland
  • 6Faculty of Environmental Sciences, Czech University of Life Sciences, Prague, Czech Republic

Abstract. Iceland is a highly active source of natural dust. Icelandic dust has the potential to affect directly the climate via dust-radiation interaction, and indirectly via dust-cloud interaction, snow/ice albedo effect and impacts on biogeochemical cycles. The impacts of Icelandic dust depend on its mineralogical and chemical composition. However, lack of data has prevented an accurate assessment of the role of Icelandic dust in the Earth system. Here, we collected surface sediment samples from five major Icelandic dust hotspots. Dust aerosols were generated and suspended in atmospheric chambers, and PM10 and PM20 fractions were collected for further analysis. We found that the dust samples primarily consist of amorphous basaltic material ranging from 8 wt% (from the Hagavatn hotspot) to 60–90 wt% (other hotspots). Samples had relatively high total Fe content (10–13 wt%). Sequential extraction of Fe to determine its chemical form shows that dithionite Fe (Fe oxides such as hematite and goethite) and ascorbate Fe (amorphous Fe) contribute respectively 1–6 %, and 0.3–1.4 % of the total Fe in Icelandic dust. The magnetite fraction is 7–15 % of total Fe and 1–2 wt% of PM10, which is orders of magnitude higher than in mineral dust from North Africa. Nevertheless, about 80–90 % of the Fe is contained in pyroxene and amorphous glass. The initial Fe solubility (ammonium acetate extraction at pH 4.7) is from 0.08–0.6 %, which is comparable to low latitude dust such as that from North Africa. The Fe solubility at low pH (i.e., 2) is significantly higher than typical low latitude dust (up to 30 % at pH 2 after 72 hrs). Our results revealed the fundamental differences in composition and mineralogy of Icelandic dust from low latitude dust. We attribute these differences to the low degree of chemical weathering, the basaltic composition of the parent sediments, and glacial processes. Icelandic dust contributes to the atmospheric deposition of soluble Fe and can impact primary productivity in the North Atlantic Ocean. The distinct chemical and mineralogical composition, particularly the high magnetite content (1–2 wt%), indicates a potentially significant impact of Icelandic dust on the radiation balance in the sub-polar and polar regions.

Clarissa Baldo et al.

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Clarissa Baldo et al.

Clarissa Baldo et al.

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We showed that Icelandic dust has a fundamentally different chemical and mineralogical composition from low latitude dust. In particular, magnetite is as high as 1–2 % of the total dust mass. Our results suggest that Icelandic dust may have an important impact on the radiation balance in the sub-polar and polar regions.
We showed that Icelandic dust has a fundamentally different chemical and mineralogical...
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