Evaluating the Status of Air Quality, Source Apportionment and Investigating the correlations with meteorological parameters over the Urban Ecosystem area of Indo-Gangetic Plain

The Indo-Gangetic Plain (IGP) is one of the most pollution-burdened and meteorologically sensitive regions worldwide, where high population load, intensive agriculture, expanding industries, and stagnant winter conditions combine to create air-quality challenges. The present study analyses the spatio-temporal variations of six key pollutants—PM₂.₅, PM₁₀, NO₂, SO₂, CO, and O₃ collected from Central pollution control board (CPCB) across major urban ecosystem area of IGP region (Agra, Ghaziabad, Meerut, Lucknow, Varanasi, and Kanpur) during 2020–2021. The period is especially informative as it encompasses the emission-suppressed COVID-19 lockdown phases of 2020 and the rapid economic recovery of 2021, providing a unique natural experiment to observe pollutant–meteorology interactions. Annual pollutant patterns show that particulate matter remained the most critical concern throughout both years. Despite large-scale mobility restrictions in 2020, PM₂.₅ and PM₁₀ annual means (55.0 ± 19.6 and 125.8 ± 46.9 µg m⁻³) remained well above national standards, indicating persistent structural sources such as traffic, industrial combustion, dust resuspension, and biomass burning. With economic activity resuming in 2021, these levels rose further (61.3 ± 17.5 and 140.1 ± 46.5 µg m⁻³), highlighting the sensitivity of the region to emission resurgence. In contrast, NO₂, SO₂, CO, and O₃ exhibited relatively modest interannual changes, reflecting more stable emission sectors and meteorological controls. Seasonal patterns showed clear contrasts across both years, with winter emerging as the most polluted period due to strong atmospheric stability, shallow boundary-layer heights, and frequent temperature inversions. Winter 2020 recorded severe particulate peaks (PM₂.₅: 115.1 ± 46.5 µg m⁻³; PM₁₀: 226.4 ± 66.5 µg m⁻³), while winter 2021 displayed similarly elevated levels driven by stagnant meteorology, fossil-fuel combustion, and regional biomass burning. Monsoon months consistently showed the cleanest air, with August 2020 reaching minimum PM₂.₅ (20.1 ± 2.1 µg m⁻³) due to wet scavenging and enhanced mixing. NO₂ and CO exhibited winter maxima, whereas O₃ peaked in pre-monsoon months under strong photochemical activity.Principal Component Analysis identified two dominant pollutant groupings explaining 86.58% of variance. The first (60.63%) represented combustion-related sources linking PM₂.₅, PM₁₀, CO, and NO₂, while the second (25.95%) reflected industrial and secondary processes associated with SO₂ and O₃.Overall, the analysis confirms the entrenched nature of particulate pollution in selected urban ecosystem areas over  IGP region and highlights the importance of coordinated emission-control strategies that are responsive to both source contributions and seasonally driven atmospheric processes.