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

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Baldo, Clarissa, Formenti, Paola, Nowak, Sophie, Chevaillier, Servanne, Cazaunau, Mathieu, Pangui, Edouard, Di Biagio, Claudia, Doussin, Jean-Francois, Ignatyev, Konstantin, Dagsson-Waldhauserova, Pavla, Arnalds, Olafur, Mackenzie, A, SHI, Zongbo
• Other Authors: SCHOOL OF GEOGRAPHY EARTH AND ENVIRONMENTAL SCIENCES UNIVERSITY OF BIRMINGHAM GBR, Partenaires IRSTEA, Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA (UMR_7583)), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: [SDE.MCG]Environmental Sciences/Global Changes; Iceland
• Online Access: https://hal.archives-ouvertes.fr/hal-03004734; https://hal.archives-ouvertes.fr/hal-03004734/document; https://hal.archives-ouvertes.fr/hal-03004734/file/acp-20-13521-2020.pdf; https://doi.org/10.5194/acp-20-13521-2020

International audience Iceland is a highly active source of natural dust. Icelandic dust has the potential to directly affect the climate via dust-radiation interaction and indirectly via dust-cloud interaction, the snow/ice albedo effect and impacts on bio-geochemical cycles. The impacts of Icelandic dust depend on its mineralogical and chemical composition. However, a 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 PM 10 and PM 20 fractions were collected for further analysis. We found that the dust samples primarily consist of amorphous basaltic materials ranging from 8 wt % (from the Hagavatn hotspot) to 60 wt %-90 wt % (other hotspots). Samples had relatively high total Fe content (10 wt %-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 (amor-phous Fe) contribute respectively 1 %-6 % and 0.3 %-1.4 % to the total Fe in Icelandic dust. The magnetite fraction is 7 %-15 % of total Fe and 1 %-2 wt % of PM 10 , which is orders of magnitude higher than in mineral dust from northern 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 % to 0.6 %, which is comparable to low-latitude dust such as that from northern Africa. The Fe solubility at low pH (i.e. pH 2) is significantly higher than typical low-latitude dust (up to 30 % at pH 2 after 72 h). 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 ...