Belwa, a small city nestled in the Muzaffarpur district of Bihar, India, occupies a relatively flat expanse of the Indo-Gangetic Plain at approximately 26.1056°N, 87.4916°E. Its elevation, typical of the region, is low-lying, contributing to limited natural air dispersion. The surrounding landscape is predominantly agricultural, characterized by intensive farming of rice, wheat, and sugarcane. This agricultural activity, while vital to the local economy, introduces particulate matter from crop residue burning and fertilizer application. The Burhi Gandak river flows nearby, influencing local humidity and potentially trapping pollutants during temperature inversions. Belwa’s position isn’t directly within a major industrial belt, but it experiences the effects of regional industrial emissions from larger centres like Muzaffarpur. The urban-rural gradient is sharp; Belwa itself is a relatively small urban centre surrounded by extensive rural farmland. This proximity means that air quality is heavily influenced by agricultural practices and biomass burning in surrounding villages. The lack of significant topographical features – hills or forests – hinders the flushing out of pollutants, making Belwa susceptible to air stagnation, particularly during calmer weather conditions. The flat terrain also means pollutants can travel long distances with minimal obstruction.

Belwa’s air quality follows a distinct seasonal pattern. The post-monsoon period, from October to November, often sees the worst conditions. The cessation of monsoon rains removes the natural cleansing effect of rainfall, while agricultural burning of crop residue after the harvest intensifies particulate matter pollution. Shallow temperature inversions are common during these cooler months, trapping pollutants near the ground. December and January bring cooler temperatures and often foggy conditions, further exacerbating pollution as vertical mixing is reduced. The summer months, from April to June, are generally better, with higher temperatures and winds aiding dispersion, though dust storms can temporarily elevate particulate matter. The monsoon season, July to September, provides a temporary respite, as rainfall washes pollutants from the air. However, increased humidity can also promote the formation of secondary pollutants. Sensitive groups – children, the elderly, and those with respiratory conditions – should avoid prolonged outdoor activity during October-November and December-January. March-April can also be problematic due to dust. Monitoring local weather patterns and avoiding peak pollution times is crucial for protecting respiratory health. The monsoon offers the most favourable conditions for outdoor activity.