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Situated on the high-altitude plateau of Kerman province at approximately 1,730 meters above sea level, Sīrjān functions as a vital industrial and agricultural nexus in southeastern Iran. The city is cradled by the central Iranian desert landscape, characterized by arid, basin-like topography that restricts natural air circulation. To the east and northeast, the rugged ranges of the Zagros foothills create a rain shadow effect, contributing to the region’s pronounced semi-arid climate. Sīrjān is strategically positioned along the corridor connecting the Persian Gulf ports to central Iran, which necessitates heavy logistical traffic that defines its urban character. The surrounding terrain is dominated by vast, salt-crusted plains and pistachio orchards, which represent the agricultural backbone of the local economy. However, the proximity of major mining operations and industrial zones, particularly those focused on mineral processing, significantly impacts the local atmosphere. The urban-rural gradient is sharp; while the city core is dense with commercial activity, the outskirts quickly transition into desolate, wind-swept desert expanses. This geographical isolation, combined with the basin-like depression of the surrounding Kerman plateau, means that pollutants—ranging from vehicular emissions along the transit routes to particulate matter from industrial mining—tend to settle over the city. The lack of significant bodies of water means there is little humidity to scrub the air, while the thermal properties of the desert floor facilitate rapid daytime heating and nocturnal cooling, often trapping dust and anthropogenic aerosols within the local boundary layer, thereby shaping the city’s complex and challenging atmospheric profile.

Sīrjān experiences a climate defined by extreme thermal variation, which dictates its seasonal air quality patterns. During the scorching summer months, high solar radiation facilitates the vertical mixing of air, yet the extreme heat often exacerbates the formation of ground-level ozone. Conversely, the transition into autumn and winter introduces the phenomenon of thermal inversions, where cold, dense air sinks into the basin, trapping pollutants from industrial emissions and heavy trucking traffic near the ground. December and January are particularly challenging; the lack of atmospheric turbulence prevents the dispersion of PM2.5 and PM10, leading to stagnant, hazy days that persist until the mid-morning sun breaks the inversion layer. Spring offers a brief reprieve, though it is frequently marred by seasonal dust storms originating from the vast, arid landscapes of central Iran. These events, driven by high-velocity winds sweeping across the plateau, significantly degrade air quality, turning the sky a muted ochre and introducing high concentrations of suspended mineral dust. For residents, the months of April and May are optimal for outdoor activity, provided there are no active dust-carrying wind events. Sensitive groups, including those with pre-existing respiratory conditions or cardiovascular ailments, should exercise extreme caution during the peak winter inversion months and the height of the spring dust season. It is advisable to monitor local weather reports for wind speed and direction, as high-velocity gusts often signal incoming desert dust. During winter evenings, staying indoors with filtered ventilation is the most effective strategy to mitigate exposure to trapped combustion particles.