- 1Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Departamento de Ciências Atmosféricas, São Paulo, Brazil (arthurdiasfreitas@usp.br)
- 2Université Clermont Auvergne, Laboratoire de Météorologie Physique, OPGC/CNRS UMR 6016, Clermont-Ferrand, France
Formaldehyde (HCHO) and nitrogen dioxide (NO2) are important precursors of tropospheric ozone through photochemical reactions. HCHO also acts as a marker for the oxidation of volatile organic compounds (VOCs). In the Metropolitan Area of São Paulo (MASP), these precursors are directly emitted by over 7 million vehicles, which burn a complex blend of ethanol and gasoline [1, 2, 3]. The present work analyzed vertical columns of HCHO and NO2 over MASP, using data retrieved from the TROPOMI sensor onboard the Sentinel-5P satellite. The analysis covered a five-year period from 2019 to 2023. A study region spanning ~6,500 km2 within the MASP was divided into 50 areas, each measuring 0.1° x 0.1° in latitude and longitude. This approach enabled the classification of the areas into distinct land-use types: 18 representing urban regions, 15 corresponding to green regions, and 17 covering transitional zones [4].
The three areas with the lowest and highest HCHO columns were two transition regions and one green region (minimum = 10.6 x 1015 molecules/cm2, extreme southwest), and three densely urbanized areas (maximum = 13.9 x 1015 molecules/cm2, central region), respectively. The three areas with the lowest and highest of NO2 columns were green regions (minimum = 2.5 x 1015 molecules/cm2, extreme southwest) and urban areas (maximum = 9.4 x 1015 molecules/cm2, central region), respectively. Both atmospheric constituents displayed higher column densities during the southern hemisphere winter (dry season).
The formaldehyde to nitrogen dioxide ratio (FNR) was calculated for each of the 50 areas, highlighting the São Paulo city center — particularly Marginal Tietê and Marginal Pinheiros — as a hotspot for ozone formation [5]. Despite its proximity to the urban center, the important Atlantic Forest (Reserve of Morro Grande) showed significantly lower concentrations of HCHO and NO2 compared to those recorded in the central areas. TROPOMI HCHO and NO2 data are proving essential for a better characterization of atmospheric chemical processes in the MASP, contributing to describe the formation of secondary pollutants, supporting the objectives of the BIOMASP+ project.
Keywords: Formaldehyde, Nitrogen Dioxide, Ozone, São Paulo megacity, TROPOMI
Acknowledgments: This work is funded and supported by BIOMASP+ Project (FAPESP 2020/07141-2) and Postgraduate Program in Meteorology (IAG-USP).
References
[1] Nogueira, T. et al., Atmosphere, 8(8), 144, 2017, https://doi.org/10.3390/atmos8080144
[2] Chiquetto, J. B. et al., Science of the Total Environment, 945, 2024, https://doi.org/10.1016/j.scitotenv.2024.173968
[3] CETESB, 2024, https://cetesb.sp.gov.br/ar/wp-content/uploads/sites/28/2024/08/Relatorio-de-Qualidade-do-Ar-no-Estado-de-Sao-Paulo-2023.pdf
[4] Pellegatti-Franco, D. M. et al., Urban Climate, 27, 293–313, 2019, https://doi.org/10.1016/j.uclim.2018.12.007
[5] Acdan, J. J. M. et al., Atmospheric Chemistry and Physics, 23(14), 7867–7885, 2023, https://doi.org/10.5194/acp-23-7867-2023
How to cite: Freitas, A., Zacharias, D., Borbon, A., and Fornaro, A.: Five years of satellite-based HCHO and NO2 monitoring over the Metropolitan Area of São Paulo, Brazil: insights from the BIOMASP+ project, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13358, https://doi.org/10.5194/egusphere-egu25-13358, 2025.
