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Hargāwān, a small city nestled within the state of Bihar, India, occupies a relatively flat expanse of the Indo-Gangetic Plain at approximately 25.1428°N, 85.5652°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 through crop residue burning and fertilizer application. Hargāwān’s position isn’t near major industrial belts, but regional brick kilns and small-scale industries contribute to localised pollution. The Phalgu River flows nearby, but its influence on air quality is limited due to its seasonal flow and the prevailing wind patterns. The urban-rural gradient is sharp; the city itself is compact, quickly giving way to agricultural fields. This proximity means pollutants generated within Hargāwān are not readily diluted by larger air masses. The city’s location within the Indo-Gangetic Plain, a known hotspot for air pollution, exacerbates these challenges, trapping pollutants during periods of low wind speed and temperature inversions. Dust storms originating from the western regions of the plain also frequently impact Hargāwān’s air quality, particularly during pre-monsoon season.

Hargāwān experiences a distinct seasonal air quality pattern dictated by the monsoon and post-monsoon cycles. October to February represents the most challenging period. Cooler temperatures lead to temperature inversions, trapping pollutants near the ground, and increased biomass burning for warmth further degrades air quality. Wind speeds are generally low during these months, hindering dispersion. March and April bring pre-monsoon conditions, marked by dust storms originating from the arid western regions, significantly increasing particulate matter concentrations. May to September is dominated by the monsoon, offering a period of relative relief. Heavy rainfall effectively washes away pollutants, and increased humidity suppresses dust. However, stagnant conditions during breaks in the monsoon can lead to localised pollution build-up. Post-monsoon, from October onwards, the burning of crop residue after the harvest contributes to a rapid decline in air quality. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit outdoor activity during October-February and periods of dust storm activity. Avoiding peak hours near agricultural areas during crop residue burning is also advisable. Monitoring local conditions and using appropriate respiratory protection when necessary is crucial.