  Using the formalism of the classical nucleation theory, we derive a novel
kinetic equation for the size and composition distribution of an ensemble of
aqueous organic aerosols, evolving via nucleation and concomitant chemical
aging. This distribution can be drastically affected by the enthalpy of
heterogeneous chemical reactions and the depletion of organic trace gases
absorbed by aerosols. A partial differential equation of second order for the
temporal evolution of this distribution is obtained from the discrete equation
of balance via Taylor series expansions. Once reduced to the canonical form of
the multidimensional Fokker-Planck equation, this kinetic equation can be
solved via the method of complete separation of variables. The new kinetic
equation opens a new direction in the development of the kinetic theory of
first-order phase transitions, while its applications to the formation and
evolution of atmospheric organic aerosols may drastically improve the accuracy
of global climate models.
