This study investigates the spatial and temporal variations in tropospheric columnar NO₂ concentrations over thermal power plant (TPP) locations surrounding Delhi, utilizing data from the TROPOMI instrument on board the Sentinel-5P satellite. The data analysis analyses yearly, seasonal and monthly variability in NO₂ and influence by meteorological parameters from 2019 to 2024. Findings reveal significantly higher NO₂ concentrations during the pre-monsoon (3.1 × 10− 5 ± 2.1 × 10−6 mol m− 2) and winter (3.0 × 10− 5 ± 3.6 × 10−6 mol m− 2), with the lowest levels recorded during the monsoon (1.8 × 10− 5 ±1.43 × 10−6 mol m− 2), followed by the post-monsoon (2.1 × 10− 5 ±2.98 × 10−6 mol m− 2). Among the monitored TPPs, the Jajjar and Indira Gandhi plants consistently exhibited the highest annual NO₂ levels, likely due to their proximity to Delhi and additional emissions from urban sources. A significant decline in NO₂ concentrations was observed in 2020 during the COVID-19 lockdown, reflecting a temporary reduction in anthropogenic activities. However, levels rebounded post-2022, with a slight decrease in 2024, except during the Jajjar and Indira TPPs. Meteorological analysis indicates that wintertime inversions and low wind speeds contribute to pollution build-up, while high-magnitude monsoon winds enhance dispersion and can transport pollutants away from urban centres. Forward trajectory modelling using HYSPLIT reveals frequent air mass transport from NCTPP and Panipat TPPs towards Delhi. The other TPPs, such as Suaratgarh, Talwandi and Harduaganj, contribute significantly lower number of transport trajectories towards Delhi than others. This study illustrates the importance of satellite-based monitoring in evaluating NO₂ concentrations from TPPs and emphasizes the necessity for season-specific policy changes and strong emission regulations. This study approach is also valuable for monitoring NO₂ concentrations over other TPPs in India and the Globe and assessing their influence on the pollutant levels of the nearby cities.
Behera et al. (Sun,) studied this question.