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

Abstract

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.

Particle‐scale characterization of volcaniclastic dust sources within Iceland

“…To summarize, these findings are consistent with earlier work (Baratoux et al, 2011;Gislason et al, 2011;Dagsson-Waldhauserová et al, 2014a;Arnalds et al, 2016;Baldo et al, 2020), which demonstrates that the geochemical and mineralogical compositions of Icelandic dust are dependent on the volcanic dust source. Such connections are useful for the reconstruction of dust transport pathways (Moroni et al, 2018;Đor dević et al, 2019).…”

“…%) and proportionately less plagioclase (20 to 25 wt. %) consistent with similar sites studied by Baratoux et al (2011) and Baldo et al (2020). Baratoux et al (2011) and Baldo et al (2020) also identify dominant minerals of pyroxene, olivine and plagioclase within thin sections of rock and sand obtained from Dyngjusandur, which is the origin of the Glacio1 collected for this study.…”

“…The SiO 2 content represents 47 to 53% of the total estimated mass for all samples and is only 1% higher than the range of values obtained for similar sites studied by Baldo et al (2020). Particle diameter and the location of the collection site within Dyngjusandur appear not to affect the phase composition, given the general similarity evident between the abundance values measured by Baratoux et al (2011) for sand particles, Baldo et al (2020) for PM 10 and PM 20 , and those reported herein for dust particles isolated by wet sieving (Fig. 6B).…”

“…6B). However, the proportion of Al 2 O 3 in the dust is marginally lower than for similar samples listed in the studies of Baratoux et al (2011) and Baldo et al (2020). The similarity shown in Fig.…”

“…The comparatively high proportion of glass (70 to 90 wt. %) reported by Baratoux et al (2011) and Baldo et al (2020) is related to the volcanic activity within glaciers. The large abundance of calcite (11 wt.…”