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Patjirwa, nestled in the state of Bihar, India, occupies a geographically significant position within the fertile Gangetic plains. Located at approximately 26.8084° N, 84.3847° E, the town’s elevation is relatively low, around 98 meters above sea level, contributing to a tendency for pollutants to accumulate, particularly during periods of atmospheric stability. The surrounding landscape is predominantly agricultural, characterized by expansive fields of rice and wheat, typical of the Indo-Gangetic Plain. This agricultural activity, while vital for the regional economy, introduces sources of particulate matter through crop residue burning, a common practice after harvest. Patjirwa’s proximity to the Ganges River, though providing a crucial water source, can also influence local weather patterns and contribute to humidity, which can trap pollutants. The urban–rural gradient around Patjirwa is gradual, with smaller villages and agricultural lands transitioning seamlessly into the town’s built environment. While Patjirwa itself is a relatively small settlement, it sits within a broader region experiencing increasing urbanization and industrial development, with larger industrial belts located further west, potentially impacting air quality through long-range transport of pollutants. The flat terrain limits natural dispersion of airborne contaminants, exacerbating the effects of local emissions and regional pollution sources. The climate is subtropical, with hot summers and a distinct monsoon season, further influencing atmospheric conditions and pollutant behaviour.

Patjirwa’s air quality experiences a distinct seasonal cycle heavily influenced by the region’s monsoon climate. The pre-monsoon months (March-May) typically see the poorest air quality, characterized by stagnant conditions and increased agricultural burning. Dry, hot winds trap pollutants close to the ground, leading to a build-up of particulate matter. Temperature inversions, common during this period, further exacerbate the problem by preventing vertical mixing of the atmosphere. The monsoon season (June-September) brings relief as increased rainfall and stronger winds naturally cleanse the air, dispersing pollutants and reducing their concentration. However, heavy rainfall can also lead to increased humidity, which, while beneficial in some respects, can contribute to the formation of secondary pollutants. The post-monsoon season (October-November) often mirrors the pre-monsoon period, with a return to drier conditions and a resurgence of agricultural burning as farmers prepare their fields for the winter crop. December and January are generally the coolest months, with occasional fog, which can trap pollutants and reduce visibility. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the pre-monsoon and post-monsoon periods, limiting outdoor activity during peak pollution times. Maintaining indoor air quality through ventilation and air purification can also be beneficial. The monsoon months offer a window of improved air quality, making them a more favourable time for outdoor pursuits, though vigilance regarding pollen counts remains important.