EGU25-13198, updated on 27 Mar 2025
https://doi.org/10.5194/egusphere-egu25-13198
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Giant Particle Size Distribution and Composition Near and In Dust Sources
Konrad Kandler1, Agnesh Panta1, Mara Montag1, Melanie Eknayan1, Hannah Meyer2, Martina Klose2, Kerstin Schepanski3, Cristina González-Flórez4,5, Adolfo González-Romero4, Andres Alastuey6, Pavla Dagsson Waldhauserová7, Xavier Querol6, and Carlos Pérez García-Pando4
Konrad Kandler et al.
  • 1Technical University Darmstadt, Institute of Applied Geosciences, Darmstadt, Germany
  • 2Karlsruhe Institute of Technology (KIT), Karlsruhe, Institute of Meteorology and Climate Research – Troposphere Research (IMKTRO), Germany
  • 3Freie Universität Berlin, Institute of Meteorology, Berlin, Germany
  • 4Barcelona Supercomputing Center (BSC), Barcelona, Spain
  • 5Danish Meteorological Institute (DMI), Copenhagen, Denmark
  • 6Institute of Environmental Assessment and Water Research – Consejo Superior de Investigaciones Científicas (IDAEA-CSIC), Barcelona, Spain
  • 7Agricultural University of Iceland, Environmental Sciences, Reykjavik, Iceland

Mineral dust is one of the key players in the Earth’s atmosphere with respect to climate and atmospheric nutrient transport. Dust spans a large size range of particle diameters, reaching from around 100 nm to more than 100 µm. While it has been assumed for a long time that the super-coarse (10 - 62.5 µm) and giant (> 62.5 µm) particles are not widely dispersed from the sources, more recent observations show that they can travel on a regional up to even intercontinental scale. Owing to the negligence and difficulty in measurement, not much information is available on this dust size range.

In the present work we have collected dust by means of a simple flat-plate deposition sampler and analyzed the collected material with electron microscopy and X-ray fluorescence, yielding information on particle size distributions and elemental composition. Samples were collected during intensive field campaigns of the FRAGMENT project in Morocco in 2019, a joint field campaign with the HiLDA project in Iceland in 2021, and the Jordan Wind erosion And Dust Investigation (J-WADI) in 2022. During all campaigns, severe dust conditions were observed with mass concentrations ranging into the tens of milligrams per cubic meter.

All observed number size distributions have in common a decrease towards submicron particles and a monotonic decrease with increasing particle size starting from 5 µm diameter. Both features are in general corroborated by online size distribution measurements in the overlap region, while the decrease towards smaller particle sizes is enhanced in the deposition sampling, most probably linked to the lower deposition speed of these particle sizes. The mean size distribution observed in Iceland has relatively more larger particles, followed by Jordan and lastly Morocco. Besides modes at around 1 µm and 5 µm, in Morocco a tertiary mode at around 70 µm in diameter gets pronounced. Mineral composition was estimated for each particle from the elemental composition. Morocco and Jordan have a similar composition with a slightly higher amount of Ca-accreted and feldspar particles in Jordan and more illite-/muscovite-like ones in Morocco. Expectedly, the composition of Icelandic dust is different, with volcanic glass, feldspars, and pyroxene/amphibole-like particles dominating. Comparing the coarse (sub-10-µm) with the super-coarse/giant (>10 µm) size range, we observe in the hot deserts less calcite for the larger particles as a common feature. The trend of a decreasing relative contribution of Fe-rich particles starting at the submicron range continues. In Iceland, we see the dominance of glassy particles still increase with increasing particle size. A big change in composition between these size classes is not observed unlike, for example, in previous measurements in Morocco, which showed a strong increase of quartz-like particles for the giant particle range. That indicates a considerable small-scale variability in freshly emitted dust plumes, dependent on their source.

How to cite: Kandler, K., Panta, A., Montag, M., Eknayan, M., Meyer, H., Klose, M., Schepanski, K., González-Flórez, C., González-Romero, A., Alastuey, A., Dagsson Waldhauserová, P., Querol, X., and Pérez García-Pando, C.: Giant Particle Size Distribution and Composition Near and In Dust Sources, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13198, https://doi.org/10.5194/egusphere-egu25-13198, 2025.