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Composition and mixing state of atmospheric aerosols determined by electron microscopy: method development and application to aged Saharan dust deposition in the Caribbean boundary layer

Kandler, Konrad and Schneiders, Kilian and Ebert, Martin and Hartmann, Markus and Weinbruch, Stephan and Prass, Maria and Pöhlker, Christopher (2018):
Composition and mixing state of atmospheric aerosols determined by electron microscopy: method development and application to aged Saharan dust deposition in the Caribbean boundary layer.
In: Atmospheric Chemistry and Physics, 18, (18), Copernicus, pp. 13429-13455, ISSN 1680-7324,
DOI: 10.25534/tuprints-00011382,
[Online-Edition: https://doi.org/10.5194/acp-18-13429-2018],
Secondary publishing via sponsored Golden Open Access, [Article]

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Item Type: Article
Origin: Secondary publishing via sponsored Golden Open Access
Title: Composition and mixing state of atmospheric aerosols determined by electron microscopy: method development and application to aged Saharan dust deposition in the Caribbean boundary layer
Language: English
Abstract:

The microphysical properties, composition and mixing state of mineral dust, sea salt and secondary compounds were measured by active and passive aerosol sampling, followed by electron microscopy and X-ray fluorescence in the Caribbean marine boundary layer. Measurements were carried out at Ragged Point, Barbados during June–July 2013 and August 2016. Techniques are presented and evaluated, which allow for statements on atmospheric aerosol concentrations and aerosol mixing state based on collected samples. It became obvious that in the diameter range with the highest dust deposition the deposition velocity models disagree by more than 2 orders of magnitude. Aerosol at Ragged Point was dominated by dust, sea salt and soluble sulfates in varying proportions. The contribution of sea salt was dependent on local wind speed. Sulfate concentrations were linked to long-range transport from Africa and Europe, and South America and the southern Atlantic Ocean. Dust sources were located in western Africa. The dust silicate composition was not significantly varied. Pure feldspar grains were 3 % of the silicate particles, of which about a third were K-feldspar. The average dust deposition observed was 10 mg m−2 d−1 (range of 0.5–47 mg m−2 d−1), of which 0.67 mg m−2 d−1 was iron and 0.001 mg m−2 d−1 phosphorus. Iron deposition was mainly driven by silicate particles from Africa. Dust particles were mixed internally to a minor fraction (10 %), mostly with sea salt and less frequently with sulfate. It was estimated that the average dust deposition velocity under ambient conditions is increased by the internal mixture by 30 % – 140 % for particles between 1 and 10 µm dust aerodynamic diameter, with approximately 35 % at the mass median diameter of deposition (7.0 µm). For this size, an effective deposition velocity of 6.4 mm s−1 (geometric standard deviation of 3.1 over all individual particles) was observed.

Journal or Publication Title: Atmospheric Chemistry and Physics
Journal volume: 18
Number: 18
Publisher: Copernicus
Classification DDC: 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften
Divisions: 11 Department of Materials and Earth Sciences > Earth Science
Date Deposited: 21 Jan 2020 09:47
Last Modified: 21 Jan 2020 09:49
DOI: 10.25534/tuprints-00011382
Official URL: https://doi.org/10.5194/acp-18-13429-2018
URN: urn:nbn:de:tuda-tuprints-113829
Additional Information:

Notice on corrigendum The requested paper has a corresponding corrigendum published. Please read the corrigendum first before downloading the article.

URI: https://tuprints.ulb.tu-darmstadt.de/id/eprint/11382
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