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Qaşr-e Shīrīn, nestled in the Kermanshah Province of western Iran, occupies a strategically significant location along the Iran–Iraq border, dramatically influencing its geography and, consequently, its air quality. The city sits at a considerable elevation of approximately 1,700 meters (5,577 feet) above sea level, within the Zagros Mountains, a formidable range that dominates the regional landscape. This high altitude contributes to cooler temperatures and frequent fog, particularly during the colder months. The surrounding terrain is characterized by rugged, semi-arid hills and valleys, largely covered in sparse vegetation and agricultural land. To the east, the landscape rises sharply into the higher peaks of the Zagros, while to the west, it gently slopes towards the plains of Iraq. The city’s urban character is relatively small and compact, reflecting its population of just over 18,000. Agriculture, primarily focused on wheat and barley cultivation, is a significant economic activity in the surrounding areas, and the use of fertilizers and occasional agricultural burning can contribute to localized air pollution. While Qaşr-e Shīrīn lacks direct proximity to major rivers or lakes, the presence of seasonal streams and springs influences local microclimates. The urban–rural gradient is relatively sharp, with the city transitioning quickly into agricultural lands and then into the mountainous terrain. The Zagros Mountains act as a barrier, influencing wind patterns and trapping pollutants, especially during periods of atmospheric stability. The border location also means potential transboundary pollution events are a consideration.

Qaşr-e Shīrīn experiences a distinct seasonal pattern in its air quality, largely dictated by its climate and topography. Winters (December-February) are typically the most challenging period. Cold air masses frequently settle into the Zagros valleys, leading to temperature inversions – a phenomenon where a layer of warm air traps cooler air near the ground, preventing pollutants from dispersing. This, combined with reduced sunlight hours and increased residential heating (often using solid fuels), results in periods of stagnant air and elevated particulate matter. Spring (March-May) brings a gradual improvement as temperatures rise and winds increase, helping to ventilate the valley. However, dust storms originating from the Mesopotamian plains to the west can significantly degrade air quality during this season, particularly in April and May. Summers (June-August) are generally the most favorable, with warmer temperatures, stronger winds, and increased convective mixing, which effectively disperses pollutants. Agricultural activities, including fertilizer application, can still contribute to localized emissions. Autumn (September-November) sees a transition period, with decreasing temperatures and increasing fog, which can lead to a gradual decline in air quality as winter approaches. Sensitive groups, such as children, the elderly, and individuals with respiratory conditions, should exercise caution during winter months and be mindful of dust storm warnings in spring. Outdoor activities are generally best enjoyed during the summer months, although vigilance regarding agricultural emissions is still advised. Periods of fog should be avoided by those with respiratory sensitivities.