A Comprehensive Characterization of Particulate Matter Pollution Over South India

Abstract

A comprehensive investigation of airborne particulate matter (PM_2.5 and PM₁₀) mass concentrations and PM_2.5/PM₁₀ ratio characteristics over South India was conducted using 5 years (2019–2023) of regulatory data. Population-based tiers were used to assess heterogeneity in PM levels across the tiers. While PM exhibited the well-understood seasonal and diurnal patterns, there was no significant difference in the PM distributions across Tier 1 (cities with population above 5 million; study period mean PM_2.5 [PM₁₀]: 36 ± 22 [72 ± 39] µg m⁻³) and Tier 2 (cities with population between 0.5 and 5 million; study period mean PM_2.5 [PM₁₀]: 36 ± 24 [79 ± 51] µg m⁻³) cities. The city-wise analysis revealed that no clear PM pattern linked to tier classification. Tier 3 (cities with population below 0.5 million) cities were found to be marginally cleaner overall (study period mean PM_2.5 [PM₁₀]: 31 ± 22 [62 ± 37] µg m⁻³), while their ratio was the highest (∼ 0.5), indicating anthropogenic source dominance. Correlation analysis suggests that (i) similar sources contribute to both PM size fractions (with stronger similarity in Tier 3 cities), (ii) lesser meteorological impact on the observed daily mean PM, and (iii) a strong regional PM influence on the observed concentrations at city level. The deseasonalized PM data showed weak annual trends (ranging between −1.6 and 0.4 µg m⁻³ year⁻¹).