Nucleation rate of particles in the lower atmosphere: Estimated time needed to reach pseudo-steady state and sensitivity to H2SO4 gas concentration

[1] Using a kinetic model, we estimate the time-needed (t0) to establish a pseudo-steady state nucleation when sulfuric acid concentration ([H2SO4]) suddenly increases to a certain fixed level. We find that t0 is roughly inversely proportional to [H2SO4]. The assumption of instantaneously achieved pseudo-steady state concentration of critical clusters, on which the classical nucleation theories are based, is no longer valid when t0 is longer than the time period that [H2SO4] can be treated as constant. Under the lower marine atmospheric conditions considered in this study, the nucleation rate predicted by ion-mediated nucleation theory is very sensitive to [H2SO4] when [H2SO4] is low (< 7 10/cm) but such a sensitivity reduces significantly as [H2SO4] increases, which is quite different from that predicted with classical binary and ternary homogeneous nucleation theories.