The charging state of aerosol populations was determined using an Ion-DMPS in Helsinki, Finland between December 2008 and February 2010. We extrapolated the charging state and calculated the ion-induced nucleation fraction to be around 1.3 % ± 0.4 % at 2 nm and 1.3 % ± 0.5 % at 1.5 nm, on average. We present a new method to retrieve the average charging state for a new particle formation event, at a given size and polarity. We improve the uncertainty assessment and fitting technique used previously with an Ion-DMPS. We also use a new theoretical framework that allows for different concentrations of small ions for different polarities (polarity asymmetry). We extrapolate the ion-induced fraction using polarity symmetry and asymmetry. Finally, a method to calculate the growth rates from the behaviour of the charging state as a function of the particle diameter using polarity symmetry and asymmetry is presented and used on a selection of new particle formation events. © 2012 Author(s).
CITATION STYLE
Gagné, S., Leppä, J., Petäjä, T., McGrath, M. J., Vana, M., Kerminen, V. M., … Kulmala, M. (2012). Aerosol charging state at an urban site: New analytical approach and implications for ion-induced nucleation. Atmospheric Chemistry and Physics, 12(10), 4647–4666. https://doi.org/10.5194/acp-12-4647-2012
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