Distinct chemical and mineralogical composition of Icelandic dust compared to North African and Asian dust: Implications for the climate
Clarissa Baldo *1, Paola Formenti 2, Sophie Nowak 3, Servanne Chevaillier 2, Mathieu Cazaunau 2, Edouard Pangui 2, Claudia Di Biagio 2, Jean-Francois Doussin 2, Konstantin Ignatyev 4, PavlaDagsson Waldhauserova 5,6, Olafur Arnalds 5, A. Robert MacKenzie 1, Zongbo Shi 1
1 School of Geography Earth and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom. cxb637@student.bham.ac.uk 2 LISA, UMR CNRS 7583, Université Paris-Est-Créteil, Université de Paris, Institut Pierre Simon Laplace (IPSL), Créteil, France
3 Plateforme RX UFR de chimie, Université de Paris, Paris, France
4 Diamond Light Source, Didcot, Oxfordshire, UK
5 Agricultural University of Iceland, Keldnaholt, Reykjavik, Iceland
6 Faculty of Environmental Sciences, Czech University of Life Sciences, Prague, Czech Republic
Iceland is among the most active sources of natural dust in the world, but there is limited knowledge on its chemical composition, mineralogy, and optical properties, which prevents an accurate assessment of its impacts on climate. 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 iron (Fe) content (10-13 wt%). About 80-90% of total Fe is contained in aluminosilicate minerals, mainly pyroxene, and in the amorphous glass. 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. The initial Fe solubility (ammonium acetate extraction at pH 4.7) is 0.08-0.6%, which is comparable to low latitude dust such as such as Saharan dust. The Fe solubility at pH 2 is significantly higher than typical low latitude dust (up to 30%).
Our results quantify the 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.