Spatio-temporal analysis of air quality in high traffic density zones of Haridwar City, India.

Urban air pollution poses a significant threat to human health and environmental quality, especially in rapidly urbanizing areas. This study aimed to analyze the spatio-temporal variations of air quality in Haridwar City, India, identifying critical pollution hotspots. A systematic air quality monitoring approach was adopted to assess the air quality at the high traffic density zones of Haridwar City. Key pollutants such as particulate matter (PM and PM) and gaseous matter (NO and SO) were monitored for 1 year starting from April 2023 to March 2024. The data was processed to calculate the air quality index (AQI) using normalization methodology and Central Pollution Control Board (CPCB) recommended methodology to rank the selected sites based on their pollution level. The data was also analyzed using principal component analysis (PCA) and cluster analysis (CA) techniques to identify pollution trends and hotspots. PM concentrations {(UKH1-103.07 to 125.37 µg/m), (UKH2-100.38 to 114.40 µg/m), (UKH3-105.88 to 119.85 µg/m), (UKH5-127.08 to 130.96 µg/m), (UKH6-126.79 to 139.11 µg/m)} exceeded permissible limits of National Ambient Air Quality Standards (NAAQS) of 24 h (100 µg/m) at all the sites except at UKH4 (92.06 to 97.51 µg/m) and 7 (43.08 to 52.09 µg/m) (control) in all seasons. PM concentrations were found below the permissible limits of NAAQS of 24 h (60 µg/m) at all the sites except at UKH5 (75.16 to 77.99 µg/m) in all seasons. Gaseous emissions (NO and SO) were found below the permissible limits of NAAQS (80 μg/m). Seasonal variations indicated elevated particulate matter levels in winter due to atmospheric stagnation. Spatial analysis identified five critical hotspots (UKH1, 2, 3, 5, and 6) with consistently poor air quality indices (AQI > 50). The study indicates the urgent need for targeted air pollution mitigation strategies like water sprinkling and the use of mist cannon to suppress the dust emissions, especially in high-risk zones.