Shāmli, a city in the western Uttar Pradesh state of India, sits at coordinates 29.4500°N, 77.3200°E, within the Indo-Gangetic Plain. This expansive, fertile plain is a defining geographical feature, contributing significantly to the region’s agricultural output, but also influencing air quality. The terrain is largely flat, with a gentle slope towards the south, impacting drainage and pollutant dispersion. Shāmli’s elevation is relatively low, around 222 meters, which can exacerbate temperature inversions, trapping pollutants near the ground. The city is not directly adjacent to a major body of water, though the Yamuna River flows nearby, influencing local humidity. Surrounding Shāmli are intensely farmed lands, primarily sugarcane and wheat, and a growing network of small-scale industries, including sugar mills and brick kilns. These industries, alongside agricultural practices like crop residue burning, are major sources of particulate matter. The urban-rural gradient is pronounced; as one moves away from the city centre, agricultural land dominates, but pollution from transport and local industry still permeates these areas. The Indo-Gangetic Plain’s inherent meteorological conditions, combined with local emission sources, create a challenging environment for maintaining clean air in Shāmli.

Shāmli experiences a distinct seasonal air quality pattern. Winter (November to February) is the most polluted period. Low temperatures create strong temperature inversions, trapping pollutants emitted from residential heating (wood and dung burning), vehicular traffic, and industrial sources. Calm winds further hinder dispersion. Fog, common during these months, exacerbates particulate matter concentrations. March and April see a slight improvement as temperatures rise and winds pick up, but dust storms originating from the western Rajasthan desert can temporarily worsen conditions. The monsoon season (July to September) generally brings relief, as rainfall washes away pollutants and increased humidity causes particles to settle. However, stagnant conditions during breaks in the monsoon can lead to localised pollution build-up. Post-monsoon (October-November) is a critical period, coinciding with the post-harvest burning of crop residue – particularly sugarcane stalks – which dramatically increases PM2.5 levels. Sensitive groups, including children, the elderly, and those with respiratory conditions, should limit outdoor activity during winter and post-monsoon periods. Avoiding peak traffic hours and using air purifiers indoors are recommended.