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Bandar-e Anzalī, nestled on the southeastern shore of the Caspian Sea in Gilan Province, Iran, occupies a geographically complex and strategically important position. The city’s urban fabric is interwoven with the natural landscape, characterized by a gradual urban–rural gradient extending inland towards the Alborz Mountains. The Caspian Sea, the largest inland body of water globally, exerts a significant influence on the local climate and, consequently, air quality. The terrain is predominantly low-lying, with elevations rarely exceeding 30 meters above sea level, creating a basin-like effect that can trap pollutants. Surrounding Bandar-e Anzalī is a mosaic of agricultural lands, primarily rice paddies and orchards, typical of the Gilan region. These agricultural zones, while vital to the local economy, contribute to seasonal particulate matter emissions, particularly during harvest periods. To the east, the foothills of the Alborz Mountains provide a natural barrier, influencing wind patterns and potentially hindering the dispersion of pollutants. Further inland, industrial activity, though less concentrated than in larger Iranian cities, exists in smaller processing plants and workshops, adding to localized pollution sources. The city’s coastal location also means it is susceptible to sea breezes, which can either disperse or concentrate pollutants depending on prevailing weather conditions. The interplay of these geographical factors – the Caspian Sea’s influence, the surrounding agricultural lands, the Alborz Mountains, and the low-lying terrain – fundamentally shapes Bandar-e Anzalī’s air quality profile.

Bandar-e Anzalī’s air quality experiences a distinct seasonal cycle heavily influenced by its Caspian Sea location and regional climate. Winters, lasting roughly from November to March, are typically characterized by cooler temperatures and frequent fog, a consequence of the sea’s moisture interacting with the colder air. This fog, while visually striking, significantly reduces air mixing and traps pollutants near the ground, leading to periods of stagnant air and potentially elevated concentrations of particulate matter. Temperature inversions, common during these months, exacerbate this issue, further hindering vertical dispersion. Spring (April-May) brings a gradual warming and increased wind speeds, aiding in pollutant dispersal and generally improving air quality. Summer (June-August) sees warmer temperatures and drier conditions, although sea breezes can provide some ventilation. Agricultural activities, including fertilizer application and harvesting, contribute to localized emissions during this period. Autumn (September-October) is often a transitional period, with a return of cooler temperatures and increased humidity, sometimes leading to fog and a decline in air quality similar to winter. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during winter months and be mindful of agricultural activities in the summer. Outdoor activities are generally more favorable during spring and summer, but vigilance is always advised, particularly on days with limited wind or dense fog. The interplay of these meteorological factors dictates the ebb and flow of Bandar-e Anzalī’s air quality throughout the year.