Nanoparticle
growth influences atmospheric particles’ climatic
effects, and it is largely driven by low-volatility organic vapors.
However, the magnitude and mechanism of organics’ contribution
to nanoparticle growth in polluted environments remain unclear because
current observations and models cannot capture organics across full
volatility ranges or track their formation chemistry. Here, we develop
a mechanistic model that characterizes the full volatility spectrum
of organic vapors and their contributions to nanoparticle growth by
coupling advanced organic oxidation modeling and kinetic gas-particle
partitioning. The model is applied to Nanjing, a typical polluted
city, and it effectively captures the volatility distribution of low-volatility
organics (with saturation vapor concentrations <0.3 μg/m3), thus accurately reproducing growth rates (GRs), with a
4.91% normalized mean bias. Simulations indicate that as particles
grow from 4 to 40 nm, the relative fractions of GRs attributable to
organics increase from 59 to 86%, with the remaining contribution
from H2SO4 and its clusters. Aromatics contribute
much to condensable organic vapors (∼37%), especially low-volatility
vapors (∼61%), thus contributing the most to GRs (32–46%)
as 4–40 nm particles grow. Alkanes also contribute 19–35%
of GRs, while biogenic volatile organic compounds contribute minimally
(<13%). Our model helps assess the climatic impacts of particles
and predict future changes.