Sources and processes controlling the formation and composition of sub-micron aerosol in the Amazon rainforest: A comprehensive in-situ study at the ATTO site in the wet season

• Applicant: Dr. Franziska Köllner
• Subject Area: Atmospheric Science
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 576884160

The Amazon rainforest, often referred to as the "Earth's green lung," is the largest tropical forest on the planet and a significant global source of biogenic aerosols. During the Amazonian wet season, the atmosphere is nearly pristine, with minimal anthropogenic pollution, resulting in low aerosol mass concentrations primarily composed of biogenic organic compounds. The formation and sources of submicron aerosol particles in the Amazon have been a topic of debate for decades. Recent hypotheses propose that biogenic salts from ground-level sources act as seeding particles for condensational growth in the Aitken and accumulation modes, rather than new particle formation within the canopy. It is further suggested that the particle growth is driven by organosulfate formation from isoprene oxidation products. Alternatively, secondary aerosol formation at higher altitudes, including isoprene-derived organic nitrates, followed by downward transport may also contribute to submicron particle composition in the Amazon boundary layer. Given the rapid changes in the Amazon, understanding aerosol sources and formation processes is crucial. Current observations lack the high temporal resolution needed to identify small-scale sources and patterns. This proposal aims to conduct in-situ measurements of submicron aerosol particles at the ATTO site during the wet season in 2026, utilizing the novel and hybrid ERICA aerosol mass spectrometer. Key research questions include the role of biogenic salts as seeding particles, the growth and composition of these particles, and the influence of high-altitude particle sources.

• DFG Programme: Research Grants