Theoretical constraints on pure vapor-pressure driven condensation of organics to ultrafine particles

Organic condensation to freshly nucleated particles contributes substantially to their growth. Here we explore a range of constraints on this process, under the assumption that gas-phase oxidation of organic vapors by hydroxy radical is forming organics with a sufficiently low volatility to condense onto particles in the 2-20 nm size range. To condense but not homogeneously nucleate, vapors need to have saturation concentrations (C*) in the 10(-3) - 10(-2) mu g m(-3) range, and this is exactly the range that gas-phase chemistry is likely to produce. At least half of the observed growth rate of ultrafine particles can be explained by these simple considerations and constraints. Citation: Donahue, N. M., E. R. Trump, J. R. Pierce, and I. Riipinen (2011), Theoretical constraints on pure vapor-pressure driven condensation of organics to ultrafine particles, Geophys. Res. Lett., 38, L16801, doi:10.1029/2011GL048115.