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Title:Insights into the single-particle composition, size, mixing state, and aspect ratio of freshly emitted mineral dust from field measurements in the Moroccan Sahara using electron microscopy
Authors:ID Panta, Agnesh (Author)
ID Kandler, Konrad (Author)
ID Alastuey, Andrés (Author)
ID González-Flórez, Cristina (Author)
ID Gonzalez-Romero, Adolfo (Author)
ID Klose, Martina (Author)
ID Querol, Xavier (Author)
ID Reche, Cristina (Author)
ID Yus-Díez, Jesús (Author)
ID Pérez García-Pando, Carlos (Author)
Files:URL https://acp.copernicus.org/articles/23/3861/2023/
 
.pdf acp-23-3861-2023.pdf (7,13 MB)
MD5: 17419B159A754275DCC925C943050E7F
 
URL https://acp.copernicus.org/articles/23/3861/2023/acp-23-3861-2023.pdf
 
Language:English
Work type:Unknown
Typology:1.01 - Original Scientific Article
Organization:UNG - University of Nova Gorica
Abstract:Abstract. The chemical and morphological properties of mineral dust aerosols emitted by wind erosion from arid and semi-arid regions influence climate, ocean, and land ecosystems; air quality; and multiple socio-economic sectors. However, there is an incomplete understanding of the emitted dust particle size distribution (PSD) in terms of its constituent minerals that typically result from the fragmentation of soil aggregates during wind erosion. The emitted dust PSD affects the duration of particle transport and thus each mineral's global distribution, along with its specific effect upon climate. This lack of understanding is largely due to the scarcity of relevant in situ measurements in dust sources. To advance our understanding of the physicochemical properties of the emitted dust PSD, we present insights into the elemental composition and morphology of individual dust particles collected during the FRontiers in dust minerAloGical coMposition and its Effects upoN climaTe (FRAGMENT) field campaign in the Moroccan Sahara in September 2019. We analyzed more than 300 000 freshly emitted individual particles by performing offline analysis in the laboratory using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectrometry (EDX). Eight major particle-type classes were identified with clay minerals making up the majority of the analyzed particles both by number and mass, followed by quartz, whereas carbonates and feldspar contributed to a lesser extent. We provide an exhaustive analysis of the PSD and potential mixing state of different particle types, focusing largely on iron-rich (Fe oxide-hydroxides) and feldspar particles, which are key to the effects of dust upon radiation and clouds, respectively. Nearly pure or externally mixed Fe oxide-hydroxides are present mostly in diameters smaller than 2 µm, with the highest fraction below 1 µm at about 3.75 % abundance by mass. Fe oxide-hydroxides tend to be increasingly internally mixed with other minerals, especially clays, as particle size increases; i.e., the volume fraction of Fe oxide-hydroxides in aggregates decreases with particle size. Pure (externally mixed) feldspar represented 3.2 % of all the particles by mass, of which we estimated about a 10th to be K-feldspar. The externally mixed total feldspar and K-feldspar abundances are relatively invariant with particle size, in contrast to the increasing abundance of feldspar-like (internally mixed) aggregates with particle size with mass fractions ranging from 5 % to 18 %. We also found that overall the median aspect ratio is rather constant across particle size and mineral groups, although we obtain slightly higher aspect ratios for internally mixed particles. The detailed information on the composition of freshly emitted individual dust particles and quantitative analysis of their mixing state presented here can be used to constrain climate models including mineral species in their representation of the dust cycle.
Keywords:mineral dust, Moroccan Sahara, electron microscopy
Publication status:Published
Publication version:Version of Record
Publication date:01.01.2023
Year of publishing:2023
Number of pages:str. 3861-3885
Numbering:Vol. 23, issue 6
PID:20.500.12556/RUNG-9073 New window
COBISS.SI-ID:195155203 New window
UDC:502.3/.7
ISSN on article:1680-7324
eISSN:1680-7324
DOI:10.5194/acp-23-3861-2023 New window
NUK URN:URN:SI:UNG:REP:BEMRDFQX
Publication date in RUNG:13.05.2024
Views:328
Downloads:3
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Record is a part of a journal

Title:Atmospheric chemistry and physics
Shortened title:Atmos. chem. phys.
Publisher:European Geophysical Society, Copernicus GmbH
ISSN:1680-7324
COBISS.SI-ID:1959012 New window

Licences

License:CC BY 4.0, Creative Commons Attribution 4.0 International
Link:http://creativecommons.org/licenses/by/4.0/
Description:This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.
Licensing start date:31.03.2023

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