Spatiotemporal analysis of tropospheric nitrogen dioxide hotspot over Lahore Division in Pakistan

This study analyzes spatial and temporal trends in tropospheric nitrogen dioxide (NO2) concentrations across the Lahore Division, Pakistan, drawing on 18 years (2007–2024) of observational data from NASA’s Ozone Monitoring Instrument (OMI) Aura satellite. This study aimed to identify the main drivers of NO2 pollution, including industrial activities, energy generation, transportation systems, and agricultural burning practices. Results indicate a marked rise in annual mean NO2 levels, climbing from an initial 2.69 × 1015 mol/cm2 in 2007 to a record 3.62 × 1015 mol/cm2 by 2016, followed by a gradual reduction to 3.14 × 1015 mol/cm2 by 2024. Vehicular emissions are the primary source, with a fleet of over 7.35 million registered vehicles by 2024, comprising more than two-thirds motorcycles (5.1 million). Industrial activities, notably inefficient brick kilns and textile dyeing facilities, substantially intensify the release of pollutants, whereas thermal power infrastructure, including the 1180 MW Quaid-e-Azam plant, contributes significantly to regional NO2 burdens. Seasonal analysis shows maximum NO2 concentrations during winter months (e.g., 5.19 × 1015 mol/cm2 in December 2017), driven by thermal inversions and increased combustion activities for heating, drop to their lowest in summer with monsoon rains, and remain moderate in spring and autumn, influenced by seasonal dispersion and agricultural activities. Atmospheric modelling through HYSPLIT backwards trajectories further identified cross-border pollutant transport from local and neighboring regions.