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Shīrvān, nestled within the Khorāsān-e Shomālī province of Iran, occupies a geographically significant position at approximately 37.4019° N, 57.9281° E. The city’s terrain is characterized by a gradual rise from the surrounding plains, situated at an elevation of roughly 1,450 meters (4,757 feet) above sea level. This elevation contributes to a cooler climate compared to lower-lying regions of Iran, but also creates conditions conducive to temperature inversions, a key factor influencing air quality. Shīrvān lies within a transitional zone between the Alborz Mountains to the west and the vast, arid landscapes of Central Asia to the east. The surrounding landscape is a mix of agricultural fields – primarily wheat and barley cultivation – and scattered steppe grasslands. The urban–rural gradient is relatively sharp; the city is bordered by agricultural land, with smaller villages and rural settlements extending outwards. While not directly adjacent to a major river, the region receives seasonal rainfall and snowmelt, contributing to groundwater resources. Industrial activity in Shīrvān is relatively limited, primarily focused on agricultural processing and small-scale manufacturing. However, the proximity to larger industrial belts in neighboring provinces, coupled with vehicular traffic, contributes to localized air pollution. The prevailing winds, often originating from the west, can transport pollutants from these areas, impacting Shīrvān’s air quality. The city’s location within a basin-like topography further exacerbates this, trapping pollutants and hindering dispersion, particularly during periods of calm weather.

Shīrvān’s air quality experiences a distinct seasonal cycle dictated by its climate and regional weather patterns. Winters (December-February) are typically the most challenging period. Cold temperatures frequently lead to the formation of strong temperature inversions, where a layer of warm air traps cooler air near the ground, preventing the vertical mixing of pollutants. This results in stagnant air and a build-up of particulate matter and other emissions. The prevalence of fog during these months further compounds the issue, reducing visibility and trapping pollutants close to the ground. Spring (March-May) brings a gradual improvement as temperatures rise and wind speeds increase, dispersing pollutants more effectively. Agricultural activities, including burning of crop residues, can contribute to localized pollution spikes during this transition period. Summers (June-August) are generally characterized by drier conditions and higher temperatures, with increased solar radiation aiding in the breakdown of some pollutants. However, dust storms originating from Central Asia can significantly degrade air quality during this season. Autumn (September-November) sees a return to cooler temperatures and a gradual increase in the likelihood of temperature inversions, though typically less severe than in winter. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during winter months, limiting outdoor activity on days with poor visibility or stagnant air. During the spring, awareness of agricultural burning is crucial, and avoiding areas with visible smoke is recommended. Dust storm alerts should be heeded during summer, and protective measures like wearing masks are advisable.