Transition Metals Reactivity: A Key Component in Aerosol Aging

Aerosol aging is a crucial process in atmospheric chemistry, referring to the changes that occur in aerosol physicochemical properties during their residence time in the atmosphere. While most studies have focused on photochemical and free-radical-driven reactions, there remains a significant knowledge gap regarding redox processes initiated by transition metals.

Transition metals are capable of readily occurring in dark conditions, without the need for free radicals to initiate the reaction. These processes take place at the surface of particles or within the condensed phase of aerosols, influencing their chemical composition and properties.

The importance of understanding transition metal reactivity lies in its potential impact on atmospheric dynamics. The formation of light-absorbing compounds is a critical area of research, as these substances can significantly affect the Earth's energy balance. Transition metals play a key role in this process, and further study is needed to fully comprehend their mechanisms.

The chemical composition of aerosols evolves over time due to physical and chemical aging processes, which are influenced by various primary and secondary sources. The light-absorbing brown carbon aerosol, for instance, includes polycyclic aromatics, humic-like substances, biopolymers, and other compounds. While the radiative forcing (RF) of non-absorbing sulfate aerosols is well understood, there remains significant uncertainty surrounding black and organic aerosols.

A large fraction of this uncertainty stems from light-absorbing particles that directly affect the radiative energy balance. The latest Intergovernmental Panel on Climate Change report highlights the need for further research in aerosol-cloud and aerosol-radiation interactions, with aerosol effective RF ranging from -0.4 to -2.1 Wm-2.

In conclusion, transition metal reactivity is a critical component of aerosol aging, influencing the chemical composition and properties of particles. Further study is needed to address knowledge gaps in this area, particularly regarding the mechanisms of formation of light-absorbing compounds and their pathways to aging. Understanding these processes is essential for improving atmospheric and climate models, which are developed based on current scientific understanding.

Transition metals reactivity