Atmospheric dust has a significant impact on air quality and human health. Based on visibility, dust events are defined as dusty days and dust storms. South Khorasan, which lies between the Karakum Desert and the Sistan Plain, is affected by dust, and many dusty days have been reported in this area. However, studies on the spread of dust have yet to be conducted. In this study, dusty days and dust storms were determined for six synoptic stations (Birjand, Boshrooyeh, Ferdows, Ghaen, Nehbandan and Tabas) from 2002 to 2018. HYSPLIT model is used to track dust trajectories to determine the main paths from Central Asia and the Middle East. In this study, HYSPLIT is used to analyze dust sources and transport pathways, highlighting the importance of wind patterns and visibility data for classifying dust events. The result shows that dust particles reached South Khorasan from the west of Iran in spring and winter and from the northeast of Iran in summer and autumn. In Nehbandan and summer, most dust storms were reported to rise from Karakum and move to the Sistan plain. The most densely dusty places are located in the northeast and south of South Khorasan. These places are the main entrances and exits for dust in South Khorasan. Finally, dust in South Khorasan is also influenced by the change of seasons. A part of the dust from the Karakum desert enters South Khorasan, and a significant part of the dust raised in South Khorasan moves towards the Sistan plain.

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