lFormation of
PM
nPhysical
attrition (10-1000 µm)
nCombustion
by-products (1-1000 µm)
nNucleation
(0.1-1 µm)
•Homogeneous nucleation:
pre-cursor air pollutants forming PM
in the atmosphere (secondary PM)
–Sulfur
dioxide
–Nitrogen
dioxide
–Ammonia
•Heterogeneous
nucleation: binding to existing
particles
–Organics
–Metals