Tsvetina Evgenieva This email address is being protected from spambots. You need JavaScript enabled to view it., Elena Vakareeva, Ljuan Gurdev, Tanja Dreischuh 

Institute of Electronics, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria

Received: December 5, 2023
Revised: March 15, 2024
Accepted: March 15, 2024

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.4209/aaqr.230304  

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Cite this article:

Evgenieva, Ts., Vakareeva, E., Gurdev, L., Dreischuh, T. (2024). Identification of Saharan-Dust Intrusions over Sofia, Bulgaria, Using Near-Ground PM10 and PM2.5 Mass Concentration Measurements. Aerosol Air Qual. Res. https://doi.org/10.4209/aaqr.230304


  • In-situ PM2.5 and PM10 mass concentration measurements at urban and rural sites.
  • Investigated influence of Saharan dust (SD) load on PM2.5, PM10, and PM2.5/PM10.
  • Increase of the rural PM10 indicates SD intrusions with high probability.
  • Increase of PM combined with a drop of PM2.5/PM10 indicates, as a rule, SD intrusion.
  • Specific aerosol situations characterized by using additional auxiliary data.


Intrusions of Saharan dust (SD) in the atmosphere over Sofia City, Bulgaria, are not a rare phenomenon. Since it can significantly affect the Earth’s radiative balance, various atmospheric processes, the climate and the living conditions on the land and in the ocean, as well as the air quality, it has been the subject of large-scale studies of considerable societal and scientific interest. In the present work, results were analyzed of: concurrent measurements of near-ground aerosol PM10 and PM2.5 mass concentrations and the aerosol’s optical and microphysical characteristics as obtained by an AERONET Cimel CE318–TS9 sun/sky/lunar photometer, the MONARCH Saharan-dust forecasting model and the HYSPLIT air-mass back-trajectory-recovering model. Data on the weather conditions in Sofia Valley and the fires in Bulgaria and neighboring countries were also considered. It was shown that the strong increases in the daily-mean PM10 mass concentration (> 50 µg m-3 or > 70 µg m-3) measured by a mountain ecological station are most frequently (74% and 86% of the cases, respectively) indications of relatively intense SD passages over the station. It was shown as well that during very intense Saharan dust intrusions over the region of Sofia (with dust load > 0.15–0.20 g m-2), the urban PM10 and PM2.5 mass concentrations noticeably increased, while the PM2.5/PM10 mass concentration ratio dropped down as a rule to values around 0.2 and below. The peculiarities found in the behavior of the particulate PM10 and PM2.5 mass concentrations contact-measured near the ground would allow one to recognize or confirm intense SD transport over Sofia and Sofia Valley.

Keywords: Atmospheric particulate matter (PM), Atmospheric aerosols, Saharan dust transport, In-situ PM measurements, Sun photometer measurements

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