Environ Monit Assess. 2026 Jun 17;198(7):735. doi: 10.1007/s10661-026-15593-7.
ABSTRACT
This study presents a comprehensive spatiotemporal assessment of key ambient air pollutants (PM2.5, PM10, SO2, NO2, NH3, O3, and CO) across seven urban and semi-urban districts of the Uttar Pradesh National Capital Region (UP-NCR), India, during 2019-2023. Despite an overall decline of approximately 23% in particulate matter concentrations over the study period, annual mean PM2.5 (88 ± 15 µg/m3) and PM10 (185 ± 28 µg/m3) levels consistently exceeded the National Ambient Air Quality Standards. Land use and land cover (LULC) analysis revealed a 7.06% expansion in built-up areas, reflecting rapid urbanization and its influence on local emission patterns. This urban growth was associated with persistent NO2 enrichment, particularly in Noida, where concentrations increased by 22%. Pronounced seasonal variability was observed, with PM2.5 concentrations peaking during the post-monsoon season particularly in Noida (200 ± 102 µg/m3) and Ghaziabad (178 ± 99 µg/m3), identified as the regional pollution hotspot. Meteorological analysis revealed strong seasonal influences on pollutant concentrations. Relative humidity exhibited positive correlations with particulate matter during winter (r ≈ 0.44-0.59), reflecting hygroscopic growth and stagnant atmospheric conditions, but strong negative correlations during the monsoon (r ≈ -0.72 to -0.95) due to efficient wet scavenging. Bivariate polar plot analysis identified stagnation-driven pollutant accumulation in densely urbanized districts and wind-induced resuspension of agricultural and crustal dust in peripheral regions. HYSPLIT backward-trajectory clustering further demonstrated substantial contributions from long-range transport originating from western and northwestern source regions during pollution episodes. These findings highlight pronounced spatial heterogeneity and seasonal dynamics in air quality, emphasizing the need for region-specific, airshed-based mitigation strategies across rapidly urbanizing peri-urban corridors.
PMID:42307838 | DOI:10.1007/s10661-026-15593-7
