The Can Gio Biosphere Reserve, considered the "green lung" of Ho Chi Minh City, faces increasing anthropogenic pressures but lacks comprehensive ground-based air quality monitoring infrastructure. This study evaluates the spatio-temporal dynamics of ambient air quality within the reserve from 2018 to 2022 using advanced remote sensing. Specifically, we utilized Sentinel-5P TROPOMI satellite data processed through the Google Earth Engine (GEE) platform to monitor trace gas concentrations, including Nitrogen Dioxide (NO2), Sulphur Dioxide (SO2), Carbon Monoxide (CO), and Ozone (O3). Rigorous Quality Assurance (QA) filters were applied, and tropospheric column densities were converted to surface concentrations for validation against Vietnam's National Technical Regulation on Ambient Air Quality (QCVN 05:2023/BTNMT).

Results indicate that overall air quality remained within national safety thresholds. Notably, NO2, SO2, and CO concentrations stabilized or gradually declined over the study period, reflecting favorable climatic dispersion and mitigation efforts. Conversely, tropospheric O3 exhibited an observable upward trend. Although satellite-derived estimates were lower than in-situ ground measurements due to spatial resolution disparities, they demonstrated a robust correlation. Ultimately, integrating Sentinel-5P data with GEE offers a rapid, cost-effective framework for continuous, large-scale air quality surveillance, effectively supplementing traditional monitoring methods.