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.