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Chandannagar, a historic port town in West Bengal, India, occupies a geographically significant position on the eastern bank of the Hooghly River, a major distributary of the Ganges. Its coordinates (22.8700° N, 88.3800° E) place it within the Ganges Delta, a low-lying alluvial plain characterized by fertile soil and a relatively flat terrain. The city’s elevation averages around 12 meters above sea level, contributing to a humid subtropical climate and limited natural dispersion of pollutants. The Hooghly River itself acts as a partial barrier, influencing local wind patterns and potentially trapping pollutants within the urban area. Surrounding Chandannagar is a mosaic of agricultural land, primarily rice paddies and vegetable farms, interspersed with small villages, creating a gradual urban-rural gradient. Further afield, the landscape transitions to more densely populated areas and industrial zones concentrated around Kolkata, approximately 50 kilometers southwest. This proximity to Kolkata’s industrial belt is a crucial factor impacting Chandannagar’s air quality, as pollutants can be transported via prevailing winds. The riverfront location, historically vital for trade and industry (particularly jute and related processing), has left a legacy of industrial activity, though much has shifted or modernized. The flat topography and dense vegetation in the surrounding delta region, while beneficial for agriculture, can also exacerbate stagnant air conditions, especially during periods of low wind speed. The city’s urban character is a blend of colonial-era architecture and modern development, with narrow, densely packed streets that can impede ventilation and contribute to localized pollution hotspots.

Chandannagar’s air quality follows a distinct seasonal pattern dictated by the region’s monsoon climate. The monsoon season, typically spanning June to September, brings relief from accumulated pollutants due to frequent rainfall and increased wind speeds, effectively flushing the atmosphere. However, the preceding pre-monsoon months (March-May) often witness a significant deterioration in air quality. High temperatures and stagnant air, coupled with increased construction activity and agricultural burning in surrounding rural areas, create conditions ripe for pollution buildup. Temperature inversions, common during this period, trap pollutants close to the ground. The winter months (November-February) present a mixed picture. While cooler temperatures can reduce some emissions, the prevalence of fog, particularly in December and January, severely restricts atmospheric mixing and traps pollutants, leading to periods of reduced visibility and potentially elevated concentrations. The post-monsoon period (October) sees a gradual improvement as rainfall decreases and wind speeds pick up. Outdoor activity is generally best enjoyed during the monsoon and post-monsoon seasons. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the pre-monsoon and winter months, limiting prolonged outdoor exposure and avoiding strenuous activity, especially on days with dense fog. Agricultural practices in the surrounding areas, including stubble burning after the harvest, contribute significantly to particulate matter during the transition periods, impacting air quality across the region.