Spatio-temporal dynamics of the evolution of atmospheric pollutants in the itasy region

Abstract

This study aims to characterize the spatiotemporal dynamics of major pollutant gases—NO₂, CO, SO₂, O₃, and CH₄—in the Itasy region of Madagascar over the period 2019-2024, using Sentinel-5P/TROPOMI satellite data series. Monthly TROPOMI data were analyzed using statistical methods (nonparametric trend tests, correlations). The results show that CO and NO₂ exhibit strong seasonal variations, with peaks at the end of the dry season, such as CO increasing from approximately 0.021 to 0.037 mol/m² between February and October, and NO₂ from 9×10⁻⁶ to 2.3×10⁻⁵ mol/m². Tropospheric ozone follows a regular annual cycle, with a maximum (0.129 mol/m²) in October (dry season) and a minimum in May. Average SO₂ remains very low throughout the year (values close to zero). Spatially, CO, NO₂, and O₃ are more concentrated around urban centers and roads (Arivonimamo, Miarinarivo) than in rural areas. In addition, methane shows an upward trend from 1830 ppb in 2019 to 1875 ppb in 2024, an increase of +2.5%. These results confirm the strong seasonality of primary pollutants linked to anthropogenic activities such as vegetation fires, traffic, and weather conditions