Karpi, a small city nestled in the state of Bihar, India, occupies a geographically significant position within the Gangetic plains. Located at coordinates 25.1612°N, 84.7299°E, the city’s terrain is predominantly flat alluvial land, characteristic of the region formed by the deposition of sediments from the Ganges and its tributaries. The surrounding landscape is intensely agricultural, dominated by rice paddies and wheat fields, reflecting Bihar’s agrarian economy. Karpi’s elevation is relatively low, contributing to limited atmospheric dispersion of pollutants. The proximity to the Ganges River, while providing a vital water source, also introduces humidity which can exacerbate certain pollution issues. While not directly within a major industrial belt, the increasing industrial activity in nearby districts contributes to regional background pollution levels. The urban-rural gradient is sharp; Karpi itself is a relatively small urban centre surrounded by a vast expanse of rural farmland. This proximity means that agricultural practices, including crop residue burning, significantly impact local air quality. The city’s location within the Indo-Gangetic Plain, known for its stagnant air masses, further compounds the challenge of pollutant dispersal, making Karpi particularly vulnerable to air pollution episodes. The lack of significant topographical features to break up wind patterns contributes to this stagnation.

Karpi experiences a distinct seasonal air quality pattern dictated by the monsoon and post-monsoon periods. The summer months (April-June) see rising temperatures and dust storms, increasing particulate matter concentrations. Hot, dry winds carry dust from the western regions, worsening air quality. October-November, following the monsoon’s retreat, is often the most polluted period. Cooler temperatures create temperature inversions, trapping pollutants near the ground, combined with increased agricultural burning of crop residue after the harvest. This period sees a significant spike in PM2.5 and PM10. The monsoon season (July-September) generally offers a respite, as rainfall washes away pollutants and increased humidity suppresses dust. However, even during the monsoon, localised pollution from vehicular traffic and small-scale industries persists. Winter (December-February) brings cool, calm conditions and fog, further trapping pollutants. Sensitive groups – children, the elderly, and those with respiratory conditions – should avoid prolonged outdoor activity during October-February. During the monsoon, while air quality improves, vigilance is still needed due to potential localised sources. Avoiding peak hours for commuting and using masks when outdoors during polluted periods are recommended.