Aerosol Size Distribution Comparison of Volcanic Ashes and Sahara Dust and Its Spatial Differences on La Palma Island

VOLKER ZIEGLER, Maximilian Weiss, Frederik Weis, Henrik Hof, Ann Katrin Grossmann, Jon Vilches Sarasate, Agnes Sauleda Brossa, Palas GmbH, Karlsruhe, Germany

     Abstract Number: 342
     Working Group: Aerosols Spanning Spatial Scales: Measurement Networks to Models and Satellites

Abstract
Dust monitoring is an important part of climate research. Its deposition on snow and glaciers for example intensify melting and dust also influence other atmospheric conditions that are related to climate change. In addition to this it also affects people’s health as deposition in the human lung can cause respiratory diseases. This wide range of effects leads to a major interest in aerosol measurements for large group of researchers. One factor of interest is the transport of dust in the atmosphere. To study this, 9 aerosol AQ Guard Smart Aerosol Spectrometers have been installed on la Palma Island during the volcano eruption in Autumn/Winter 2021.

The devices were installed around the volcano with focus on the most affected areas but also on the far side of the mountain chain dividing the island in east and west part. Aerosol size and number concentration as well as particulate matter values were measured from mid of November until mid-February thus covering a period with Volcanic activities (until 13.12.2021) and without. Additionally, we also captured two days of airborne Sahara Sand dust washing over the Canary Islands.

Local differences in particulate matter readings
The local differences in particulate matter during the volcano eruption were studied with the data obtained from the 9 devices and found to vary depending on wind conditions. Especially the difference between the east and west site of la Palma was found to be very pronounced which is in accordance with the island being divided by a mountain chain.

Differences in aerosol composition
The particle size distribution of the aerosol during the volcano eruption (= airborne volcanic ashes) and the Sahara Sand Dust event (= airborne sand dust) can be found in Figure 1 together with an exemplary size distribution of normal ambient air at the same location. While sand dust influences the whole captured particle size range, volcanic dust is found to be much coarser.

References:
[1] C.Milford et al., Impact of the 2021 La Palma volcanic eruption on air quality: Insights from a multidisciplinary approach, Celia Milford, Carlos Torres et al, Science of the Total Environment (2023)