Dighwāra, a small city nestled in the state of Bihar, India, occupies a geographically significant position along the banks of the Gandak River, a major tributary of the Ganges. Its coordinates (25.7443° N, 85.0100° E) place it within the fertile Gangetic Plain, a vast alluvial landscape characterized by relatively flat terrain and rich, loamy soils. The surrounding landscape is predominantly agricultural, with extensive fields of rice, wheat, and maize stretching as far as the eye can see. This proximity to intensive agricultural practices contributes to seasonal particulate matter pollution, particularly from crop residue burning. Dighwāra’s elevation is low, approximately 128 meters above sea level, which, combined with the flat topography, limits natural air dispersion. The city’s location within the Indo-Gangetic Plain also means it’s susceptible to the regional weather patterns that often trap pollutants. While the Gandak River offers some localized cooling and potential for moisture to scavenge pollutants, its impact is limited by the scale of regional pollution sources. The urban–rural gradient around Dighwāra is gradual, with small villages and agricultural hamlets blending seamlessly into the city’s periphery. Further afield, industrial zones concentrated in larger Bihar cities, such as Patna, can contribute to transboundary air pollution events. The lack of significant natural barriers and the prevailing wind patterns often funnel pollutants towards Dighwāra, exacerbating local air quality challenges.

Dighwāra’s air quality follows a distinct seasonal pattern dictated by the region’s monsoon climate. The monsoon season, typically from June to September, brings relief from accumulated pollutants as frequent rainfall effectively washes particulate matter from the atmosphere. Humidity also increases, reducing the suspension of dust particles. However, the pre-monsoon period (March-May) is often characterized by a significant deterioration in air quality. High temperatures and stagnant air conditions, frequently accompanied by dense fog, create a meteorological inversion – a layer of warm air trapping cooler air and pollutants near the ground. This inversion prevents vertical mixing, leading to a build-up of pollutants. The post-monsoon season (October-November) witnesses a resurgence of agricultural burning as farmers clear crop residue, releasing substantial amounts of smoke and particulate matter. This period is particularly challenging for vulnerable populations. Winter months (December-February) are generally colder, with frequent fog episodes further hindering air dispersion and trapping pollutants. Outdoor activities are best avoided during the pre-monsoon and post-monsoon periods, especially for children, the elderly, and individuals with respiratory conditions. During the monsoon, while air quality improves, the increased humidity can still trigger discomfort for those with allergies or asthma. Maintaining indoor air quality through ventilation and air purifiers is advisable throughout the year, with particular emphasis during periods of elevated pollution.