New particle formation of ternary droplets in the atmosphere — a steady-state nucleation kinetics approach

Abstract

A self-consistent expression for the kinetics of ternary nucleation is developed based on the nucleation flux theory derived by Langer, 1969, Annals of Physics 54, 258–275. The method for obtaining the ternary nucleation flux is based on the solution of a Fokker–Planck equation for the concentration of clusters where both number and cluster energy fluctuations are included. The theory is applied to a nonideal solution of water–sulphuric acid that is nonideally mixed with ammonia. The nucleation rates predicted for this ternary system studied show a considerable increase on the nucleation rate compared to the binary water–sulphuric acid system for gaseous concentrations of ammonia which are likely to occur in the atmosphere. The results of the present study are in qualitative agreement with current laboratory and theoretical studies where a considerable enhancement in the nucleation rate is observed with the addition of tens of parts per trillion by volume of NH 3 in the binary H 2SO 4–H 2O system.