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Sāhar, a small town nestled in the fertile plains of Bihar, India, occupies a geographically significant position within the Gangetic Basin. Located at approximately 26.54°N, 85.86°E, its coordinates place it squarely within a region characterized by alluvial soil and a remarkably flat terrain, rarely exceeding 150 meters above sea level. The surrounding landscape is predominantly agricultural, a patchwork of rice paddies, maize fields, and pulse crops, typical of the Indo-Gangetic Plain. This intensive agricultural activity, while vital for the regional economy, contributes to seasonal air pollution through biomass burning during harvest periods. Sāhar’s proximity to the Ghaghara River, though providing a source of water and irrigation, also influences local humidity and can exacerbate the trapping of pollutants under certain meteorological conditions. The town sits on the edge of a gradual urban–rural gradient, transitioning from the dense population centers of larger Bihar cities to the dispersed rural settlements of the hinterland. There are no major industrial belts immediately adjacent to Sāhar, however, the town serves as a regional market center, with increased vehicular traffic contributing to localized pollution. The flat topography and lack of significant natural barriers mean that pollutants, once released, tend to linger, particularly during periods of low wind speed. The regional climate, dominated by monsoon patterns and hot summers, further complicates air quality management, creating conditions conducive to both particulate matter accumulation and ozone formation. The overall geographic setting presents a unique challenge for air quality, balancing agricultural needs with the health of the local population.

Sāhar’s air quality follows a distinct seasonal pattern dictated by the region’s monsoon climate. The pre-monsoon months (March-May) are typically the most challenging, characterized by hot, dry conditions and frequent temperature inversions. These inversions trap pollutants close to the ground, leading to a noticeable increase in particulate matter and other emissions. Agricultural burning, a common practice for clearing fields after the harvest, significantly contributes to this pollution load. The monsoon season (June-September) brings relief, with increased rainfall and stronger winds dispersing pollutants. However, heavy rainfall can also lead to increased humidity and the formation of secondary pollutants. Post-monsoon (October-November) sees a return to drier conditions, with agricultural burning again becoming a major factor. The winter months (December-February) are often marked by dense fog, which further restricts atmospheric mixing and traps pollutants, creating periods of poor visibility and elevated air quality concerns. 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 hours. During the fog-laden winter months, indoor air quality also becomes a concern, necessitating proper ventilation and air purification measures. The interplay of temperature, wind patterns, and agricultural practices creates a complex and dynamic air quality profile for Sāhar, requiring targeted mitigation strategies throughout the year.