Assessing atmospheric pollution in Asian major cities through sentinel-5p and google earth engine: a remote sensing approach

The climate, economic activity, and urbanization affect air quality in many Asian nations. Seasonal variations exacerbate pollution, which impacts public health and visibility. Governments, therefore, pass legislation and implement green initiatives to improve the situation. This study examines the spatiotemporal changes in Aerosol Optical Depth (AOD), Nitrogen Dioxide (NO₂), Sulfur Dioxide (SO₂), and Methane (CH₄) in Delhi, Kuala Lumpur, Bangkok, Dhaka, and Islamabad between 2019 and 2023 using MODIS data, Sentinel-5P, and Google Earth Engine (GEE). The results show significant fluctuations, with AOD levels peaking in Kuala Lumpur (3.98 in 2019) and Dhaka (1.21 in 2023), indicating high particulate pollution. NO₂ concentrations were highest in Dhaka (0.00028 mol/m² in 2022) and Delhi (0.00024 in 2021) due to increasing vehicular emissions, and SO₂ levels showed peaks in Islamabad (0.00034 mol/m² in 2019, 0.00036 in 2023), reflecting industrial and power plant emissions. Landfills and wastewater treatment were the primary sources of the highest CH₄ concentrations in Dhaka (2100.27 mol fraction in 2019, 2137.89 in 2022), Kuala Lumpur (1924.96 in 2020), Delhi (1947.82 in 2023), and Bangkok (1965.97 in 2021). The COVID-19 lockdowns in 2020–2021 caused a brief drop in NO₂ and SO₂, but a subsequent recovery in industrial activity after the pandemic indicated a return to pre-lockdown levels. Policy-driven pollution control measures, such as enhanced waste management, sustainable transportation, and industrial emission regulations, are essential, according to the report. Future research should integrate high-resolution satellite data with ground-based observations for more accurate air quality assessments and develop more targeted mitigation strategies.