Sītāmarhi Air Quality Index (AQI)

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Sītāmarhi, nestled in the fertile plains of Bihar, India, occupies a geographically significant position within the Gangetic Basin. Located at approximately 26.6000° N latitude and 85.4800° E longitude, the city’s terrain is predominantly flat, characteristic of the Indo-Gangetic Plain. The elevation is relatively low, averaging around 128 meters (420 feet) above sea level, contributing to a tendency for pollutants to accumulate, particularly during periods of atmospheric stability. Sītāmarhi’s location is bordered by expansive agricultural lands, a crucial element of the regional economy, but also a potential source of seasonal biomass burning contributing to particulate matter. The city sits near the Nepal border, influencing regional weather patterns and potentially impacting transboundary pollution events. While not directly adjacent to a major river, the region is well-drained by smaller tributaries of the Ganges, impacting local humidity and influencing atmospheric mixing. The urban–rural gradient around Sītāmarhi is gradual, with agricultural fields and small villages transitioning into the city’s built environment. This proximity to agricultural zones means that agricultural practices, including crop residue burning after harvests, significantly impact the city’s air quality. The surrounding landscape is largely dominated by farmland and scattered settlements, with limited industrial zones directly adjacent to Sītāmarhi, though regional industrial belts further afield can contribute to long-range transport of pollutants. The flat topography and low elevation exacerbate the effects of temperature inversions, trapping pollutants close to the ground.

Sītāmarhi’s air quality follows a distinct seasonal pattern dictated by the region’s monsoon climate. The pre-monsoon season (March-May) typically witnesses the poorest air quality. Rising temperatures and decreasing wind speeds create stable atmospheric conditions, frequently leading to temperature inversions that trap pollutants near the surface. Agricultural burning of crop residue after the winter harvest is a major contributor during this period, releasing significant amounts of particulate matter and other harmful gases. 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 stagnant air conditions in certain areas. The post-monsoon season (October-November) sees a return to more stable conditions, with cooler temperatures and reduced rainfall, but agricultural burning continues, albeit at a reduced intensity compared to the pre-monsoon period. Winter months (December-February) are generally characterized by colder temperatures and frequent fog, which further restricts atmospheric mixing and can exacerbate pollution. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should limit outdoor activity during the pre-monsoon and post-monsoon seasons, particularly on days with dense fog. Maintaining indoor air quality through ventilation and air purifiers is also advisable. During the monsoon, while air quality improves overall, periods of heavy rainfall and humidity can still trigger respiratory issues for some individuals. Awareness of local weather forecasts and air quality information is crucial for making informed decisions about outdoor activities throughout the year.