The heat-pollution paradox: understanding the relationship between land surface temperature and air pollution in a heavily polluted megacity

In rapidly urbanizing megacities, increasing land surface temperature (LST) and acute air pollution present considerable environmental and public health issues. Urban sprawl, industrial discharges, and automotive emissions degrade air quality, while heat-absorbing surfaces exacerbate urban heat island (UHI) phenomena. Comprehending the correlation between LST and air pollution is essential, as elevated temperatures can exacerbate pollutant concentrations via photochemical reactions and meteorological alterations. This study aims to assess the relationship between LST and air pollution during winter and summer in Delhi (India) using Remote Sensing and National Air Quality Monitoring Program (NAMP). The findings showed that the LST in Delhi exhibited seasonal variation, with summer LST reaching a maximum of 31.08 °C (mean: 28.99 °C) and winter LST declining to 16.30 °C (mean: 18.29 °C). Elevated LST were recorded in the northern, eastern, and western regions during the summer season. Air pollution exacerbated in winter, with particulate matter i.e. PM_2.5 and PM₁₀ concentrations attaining 277.13 μg/m³ and 228.33 μg/m³, respectively, whilst O₃ concentrations peak in summer at 41.08 μg/m³. The core areas maintained higher LST than the transitional zones. PM₁₀ exhibited a strong correlation with LST (winter: 0.611, summer: 0.222), affecting heat retention, but CO and O₃ demonstrated weak correlations relationships. Increased winter PM₁₀ levels (0.767) correlated with heightened summer surface UHI (SUHI), underscoring the significance of PM in warming. The study emphasized the necessity of targeted mitigation strategies, such as the expansion of urban natural infrastructure, to mitigate LST and air pollution. Policies should prioritize the integration of heat mitigation measures into city planning, the enhancement of air quality monitoring, and the regulation of winter PM levels.