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Dharhara, Bihar, situated at approximately 25.2543° N, 86.4030° E, occupies a geographically significant position within the fertile Gangetic plains of India. The city’s terrain is predominantly flat, characteristic of the Indo-Gangetic Plain, with an elevation of roughly 58 meters above sea level. This low-lying topography, while conducive to agriculture, presents challenges regarding air quality dispersion. Dharhara lies within a region heavily reliant on agriculture, particularly rice and maize cultivation, contributing to seasonal biomass burning and associated particulate matter. The surrounding landscape is dominated by agricultural fields interspersed with small villages, creating a gradual urban-rural gradient. While not directly adjacent to a major river, Dharhara benefits from proximity to the Ganges River, approximately 50 kilometers to the north, influencing regional humidity and weather patterns. The city’s location within the broader Bihar industrial belt, though not a primary industrial hub itself, experiences indirect impacts from nearby manufacturing and processing facilities. The flat, expansive terrain limits vertical mixing of pollutants, particularly during periods of atmospheric stability. Prevailing wind patterns, often influenced by the monsoon system, play a crucial role in dispersing or concentrating pollutants. The lack of significant natural barriers further exacerbates the potential for pollutants to accumulate, especially during calmer weather conditions. The surrounding agricultural practices, combined with the regional industrial activity, create a complex interplay of factors impacting Dharhara’s air quality.

Dharhara’s air quality exhibits a distinct seasonal pattern dictated by the region’s monsoonal climate. The pre-monsoon season (March-May) typically witnesses the poorest air quality, driven by agricultural residue burning following the harvest of winter crops. Farmers often resort to this practice to quickly clear fields for the next planting season, releasing significant quantities of particulate matter and other pollutants into the atmosphere. The prevailing dry and warm conditions during this period exacerbate the problem, as lower humidity allows particulate matter to remain suspended for longer. The monsoon season (June-September) brings a welcome respite, with increased rainfall and stronger winds effectively flushing out pollutants. However, heavy rainfall can also lead to increased humidity and stagnant air conditions in certain areas. The post-monsoon season (October-November) sees a gradual return of drier conditions and a resurgence of agricultural burning, though often less intense than in the pre-monsoon period. Winter months (December-February) are generally characterized by cooler temperatures and frequent fog, which traps pollutants near the ground, leading to localized episodes of poor air quality. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the pre-monsoon and winter months, limiting outdoor activities during peak pollution periods. Maintaining indoor air quality through ventilation and air purification can also be beneficial. The interplay of wind patterns, temperature inversions, and agricultural practices creates a dynamic air quality profile throughout the year, demanding continuous monitoring and targeted mitigation strategies.