Date of Publication :10th July 2025

Abstract: Air quality in the Northwest Himalayas is affected by meteorological factors, seasonal variations, and elevation-stratified dynamics. This study analyzes the influence of temperature, humidity, mixing height and precipitation on major pollutants—PM2.5, PM10, SO2, CO, O3, and NO2—using data from 2010 to 2024. Results show that PM10peaks in winter due to atmospheric stagnation and biomass burning, while monsoon rainfall reduces pollution through wet deposition whereas PM2.5 peaks in monsoon season due to formation of secondary aerosols in upper Himalayas. Temperature correlates negatively with pollutant levels, and wind speed and humidity show season- dependent effects. Elevation plays a critical role in air quality variation. Lower elevations (below 2,000m) record higher pollution levels due to anthropogenic activities and valley entrapment. In contrast, higher altitudes (above 3,500m) benefit from stronger winds and fewer emissions, enhancing dispersion. PM2.5 is particularly sensitive to humidity because of the precursor gas SO2 that further oxidizes to SO4 that contributes to PM2.5, aggravating pollution in valleys and upper elevations. Additionally, pollutant transport from the Indo- Gangetic Plain worsens air quality in the lower Himalayas during winter and post-monsoon. These findings highlight the need for elevation-specific, seasonally adaptive air quality strategies. The study emphasizes regional cooperation and targeted policies to mitigate pollution and reduce associated health risks in the Himalayan region.

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