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Bahār is a city in Hamadān Province, Iran, situated in the Zagros Mountains at an elevation of approximately 1,700 meters above sea level, which significantly influences its air quality dynamics. Located about 15 kilometers southeast of the provincial capital Hamadān, Bahār lies within a fertile agricultural plain known for its fruit orchards and wheat fields, creating a distinct urban–rural gradient where farming activities contribute particulate matter during planting and harvest seasons. The city's position in a valley surrounded by mountain ranges, including the Alvand range to the west, often traps pollutants under temperature inversions, especially during colder months. Proximity to Hamadān, a larger urban center with industrial zones, means Bahār is occasionally affected by regional pollution transport via prevailing westerly winds. No major bodies of water are nearby, reducing natural cleansing effects, while the semi-arid climate leads to dust resuspension from dry soils. The urban character of Bahār, with its growing population and general urban pollution sources like vehicle emissions and residential heating, combines with its topographic setting to create localized air quality challenges, particularly when atmospheric stability prevents dispersion.

In Bahār, air quality follows a distinct seasonal pattern shaped by its high-altitude continental climate. During winter, from December to February, cold temperatures and frequent temperature inversions trap pollutants near the ground, leading to peak pollution episodes; this is exacerbated by increased use of heating fuels, making these months the least favorable for outdoor activities, especially for sensitive groups like children and the elderly who should limit exposure. Spring, from March to May, sees improved conditions as rising temperatures and stronger winds help disperse pollutants, though occasional dust storms from surrounding drylands can cause temporary spikes. Summer, from June to August, offers the best air quality with warm, dry weather and consistent breezes that enhance ventilation, making it ideal for outdoor pursuits; however, ozone formation may occur on hot, sunny days. Autumn, from September to November, brings a gradual decline in air quality as temperatures drop and atmospheric stability increases, with pollution building up towards late autumn. Throughout the year, fog is rare, but calm conditions in valleys can lead to accumulation of emissions, advising residents to monitor local air quality reports and plan activities during midday when dispersion is typically better.