Aerosol Formation and Dynamics
How aerosol particles are born by nucleation and grow, coagulate and are removed, shaping the atmospheric particle population.
Definition
Aerosol formation and dynamics is the study of the microphysical processes that create aerosol particles and govern the time evolution of their number and size distribution.
Scope
Covers new particle formation by gas-to-particle nucleation, condensational growth of nanoparticles, Brownian coagulation, the modal structure of aerosol size distributions, dry deposition and wet scavenging, and the general dynamic equation that governs the evolving particle population.
Core questions
- How do new particles nucleate from atmospheric vapours?
- What processes move particles between the nucleation, accumulation and coarse modes?
- How are aerosols removed from the atmosphere?
Key theories
- General dynamic equation for aerosols
- A continuity equation for the particle size distribution that combines nucleation, condensation, coagulation and removal to predict the evolution of the aerosol population.
Mechanisms
New particles form when low-volatility vapours such as sulfuric acid cluster and overcome the nucleation barrier, then grow by condensation of additional vapour. Coagulation merges small particles, shifting number toward larger sizes and producing the characteristic nucleation, Aitken, accumulation and coarse modes. Removal occurs through dry deposition, important for the largest and smallest particles, and through wet scavenging in clouds and precipitation, which dominates the lifetime of accumulation-mode particles.
Clinical relevance
Particle dynamics set the concentration and size of airborne particles relevant to health, visibility, and the supply of cloud condensation nuclei that influence climate.
History
The dynamics of aerosol populations were formalized in the latter twentieth century, and field campaigns since the 1990s, notably those led by Kulmala and colleagues, established new particle formation as a widespread atmospheric phenomenon.
Key figures
- Markku Kulmala
- John Seinfeld
Related topics
Seminal works
- kulmala2004
- seinfeldPandis2016
Frequently asked questions
- What is new particle formation?
- It is the spontaneous creation of fresh aerosol particles when trace vapours such as sulfuric acid nucleate into tiny clusters that then grow, a major source of atmospheric particle number.