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<p>Nitrogen dioxide (NO<sub>2</sub>), a major component of ambient air pollution, has adverse effects on human health, the environment, and even the climate. Therefore, the current study analyzes spatiotemporal patterns, identifies hotspots, and explores the potential sources and driving factors of NO<sub>2</sub> over Punjab from 2018 to 2025 using satellite remote sensing observations. The results indicate an average NO<sub>2</sub> concentration of about 37.37&#xa0;µmol/m<sup>2</sup> during the study period. The high monthly concentration is observed in November. Seasonal peak NO<sub>2</sub> is observed in winter, followed by autumn, summer, and spring. The hotspot analysis identifies most of the NO<sub>2</sub> hotspots in northeastern Punjab, including Lahore, Sheikhupura, Kasur, Nankana Sahib, Gujranwala, and Faisalabad, with z-scores ≥ 3.129. The average concentration in these hotspot areas is 92.31&#xa0;µmol/m<sup>2</sup> (Lahore), 65.07&#xa0;µmol/m<sup>2</sup> (Sheikhupura), 59.11&#xa0;µmol/m<sup>2</sup> (Kasur), 54.42&#xa0;µmol/m<sup>2</sup> (Nankana Sahib), 50.65&#xa0;µmol/m<sup>2</sup> (Gujranwala), and 50.5&#xa0;µmol/m<sup>2</sup> (Faisalabad). The road transportation sector is found to be the major contributor to high NO<sub>x</sub> emissions. The average emission from this sector is 1.87 × 10<sup>–11</sup> kgm<sup>−2</sup>&#xa0;s<sup>−1</sup>. The road traffic sector accounts for ~ 33.88% of total NO<sub>x</sub> emissions in Punjab. In addition to local emissions, external transport of NO<sub>2</sub> from India and Afghanistan may also contribute to increasing NO<sub>2</sub> concentration over Punjab. This is indicated by the PSCF and CWT analyses based on the HYSPLIT backward trajectories and NO<sub>2</sub> concentration. Moreover, wavelet analysis also suggests a strong statistically significant association between NO<sub>2</sub> and meteorological factors, landscape features, and nighttime light.</p>

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Assessment of spatio-temporal dynamics of tropospheric NO2 and covariates using the wavelet analysis: a Punjab case study

  • 期刊论文

  • 发表日期：

    2026年7月11日

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  • Ayesha Mariam,
  • Zia Ul Haq,
  • Syeda Adila Batool

摘要

Nitrogen dioxide (NO2), a major component of ambient air pollution, has adverse effects on human health, the environment, and even the climate. Therefore, the current study analyzes spatiotemporal patterns, identifies hotspots, and explores the potential sources and driving factors of NO2 over Punjab from 2018 to 2025 using satellite remote sensing observations. The results indicate an average NO2 concentration of about 37.37 µmol/m2 during the study period. The high monthly concentration is observed in November. Seasonal peak NO2 is observed in winter, followed by autumn, summer, and spring. The hotspot analysis identifies most of the NO2 hotspots in northeastern Punjab, including Lahore, Sheikhupura, Kasur, Nankana Sahib, Gujranwala, and Faisalabad, with z-scores ≥ 3.129. The average concentration in these hotspot areas is 92.31 µmol/m2 (Lahore), 65.07 µmol/m2 (Sheikhupura), 59.11 µmol/m2 (Kasur), 54.42 µmol/m2 (Nankana Sahib), 50.65 µmol/m2 (Gujranwala), and 50.5 µmol/m2 (Faisalabad). The road transportation sector is found to be the major contributor to high NOx emissions. The average emission from this sector is 1.87 × 10–11 kgm−2 s−1. The road traffic sector accounts for ~ 33.88% of total NOx emissions in Punjab. In addition to local emissions, external transport of NO2 from India and Afghanistan may also contribute to increasing NO2 concentration over Punjab. This is indicated by the PSCF and CWT analyses based on the HYSPLIT backward trajectories and NO2 concentration. Moreover, wavelet analysis also suggests a strong statistically significant association between NO2 and meteorological factors, landscape features, and nighttime light.