Characterization of particulate matter ratios and dust resuspension dynamics in the urban airshed of Bengaluru, Karnataka

In rapidly urbanizing tropical megacities, source apportionment of particulate matter is often complicated by the interaction between combustion emissions and crustal resuspension, and Bengaluru represents this challenge. This study characterizes the city's airshed during 2018–2024 using high-resolution data from 13 Continuous Ambient Air Quality Monitoring Stations (CAAQMS) obtained from the Central Pollution Control Board (CPCB) open-access portal. Three complementary approaches were applied: stoichiometric decoupling of PM₂.₅ and PM₁₀ fractions, unsupervised k-Means clustering to identify pollution regimes, and Principal Component Analysis (PCA) with Varimax rotation to distinguish dominant sources. Clustering identified three distinct regimes: a combustion-dominated winter regime (Rf/c > 0.65) strongly associated with traffic emissions, a baseline urban regime representing equilibrium conditions, and a dust-dominated pre-monsoon regime (March–May). During the pre-monsoon period, the PM₂.₅/PM₁₀ ratio declined to approximately 0.44 due to increased coarse particulate matter (PMcoarse). PCA corroborated this separation by identifying an independent Resuspension Factor explaining 21.2% of the total variance. Regression analysis further supported these findings, with the PM₂.₅–PM₁₀ slope decreasing sharply in summer (β = 0.38, R² = 0.51), indicating coarse dust accumulation independent of the fine-particle baseline. Elevated weekend coarse particulate concentrations despite reduced traffic further confirmed persistent road dust reservoirs. These findings demonstrate that effective air-quality management should complement tailpipe-emission controls with non-exhaust measures, including systematic vacuum road sweeping, to mitigate Bengaluru's resuspension-driven summer particulate peak.