NO₂ Emission Estimation in Ho Chi Minh City, Vietnam Using Modeling and OMI Satellite Data

Nitrogen dioxide (NO₂) in the air at concentrations exceeding permissible levels impacts environmental quality and human health. In addition, NO₂ is also a precursor to ozone and an agent that creates acid rain that affects the habitat of organisms. NO₂ emission inventories are the first and most important step, especially in urban or industrial production areas. This study assesses NO₂ emissions in Ho Chi Minh City (HCMC), Vietnam-a large city with high traffic and industrial activity but limited published emission data. Using the Lifetime-Modified Accumulation Method (LMAM), we analyze tropospheric NO₂ column data from the OMI/Aura satellite (2019-2024) to estimate spatial and temporal emission trends. The results showed an average emission rate of 6.56 × 10¹⁵ molecules cm⁻² h⁻¹ in 2019, decreasing to 5.79 × 10¹⁵ molecules cm⁻² h⁻¹ in 2020 due to the COVID-19 lockdown. Emissions were highest in urban and industrial areas and lowest in suburban areas. The LMAM model demonstrated a strong correlation with TROPESS Chemical Reanalysis (TCR) NO_x data (Spearman's r = 0.71 in 2019; r = 0.70 in 2020), confirming its reliability for trend analysis. Long-term trends reflect the socioeconomic impact: a sharp decline during the pandemic (2020-2021) followed by a recovery to 1.3 × 10¹⁶ molecules cm⁻² h⁻¹ in 2023-2024 when economic activities resume. This result can provide information on NO₂ emissions as a reference for future city emission control policies and inventory plans.