Kinetic nucleation and ions in boreal particle formation events

Abstract

In order to gain a more comprehensive picture on different mechanisms behind atmospheric particle formation, measurement results from QUEST 2-campaign are analyzed with an aid of an aerosol dynamic model. A special emphasis is laid on air ion and charged aerosol dynamics. Conducted model simulations indicate that kinetic 5 nucleation of ammonia and sulphuric acid together with condensation of sulphuric acid and low-volatile organic vapours onto clusters and particles explain basic features of particle formation events as well as ion characteristics. However, observed excess of negative ions in the diameter range 1.5-3 nm and overcharge of 3-5 nm particles demonstrate that ions are also involved in particle formation. These observations can 10 be explained by preferential condensation of sulphuric acid onto negatively charged clusters and particles. According to model simulations, the relative contribution of ionbased particle formation seem to be smaller than kinetic nucleation of neutral clusters. Conducted model simulations also corroborate the recently-presented hypothesis according to which a large number of so-called thermodynamically stable clusters (TSCs) 15 having a diameter between 1-3 nm exist in the atmosphere. TSCs were found to grow to the observable sizes only under favorable conditions, e.g. when the pre-existing particle concentration was low. 25ance of Earth (e.g. Ramanathan et al., 2001). In a view of these uncertainties, detailed 3912 ACPD 4, 2004

Charged and total particle formation and growth rates during EUCAARI 2007 campaign in Hyytiälä

“…The term CoagS 2 denotes an average coagulation sink for the 2 nm particles . The sink was calculated for every 10 min from the background particle size distribution measured by the DMPS system, with hygroscopicity effects estimated as in Laakso et al (2004). The values of the CoagS 2 and the N 2−3 were averaged over the same selected period that was used to calculate rate of change, dN 2−3 /dt.…”

“…E. Manninen et al: Charged and total particle formation and growth rates air ion spectrometers (Mirme et al, 2007;Tammet, 2006). However, the concentrations of small ions are usually so low that they cannot solely explain the observed new particle formation events (Laakso et al, 2004). The current commercial instruments detect particles down to the 3-nm size.…”

Detecting charging state of ultra-fine particles: instrumental development and ambient measurements

“…A preliminary version of this device was utilized already by Mäkelä et al (2003) but the results remained unpublished. A similar, but less sophisticated than the current version of this device was also described by Laakso et al (2004). After describing the instrument and its measurement principles, we present a laboratory verification of the instrument.…”

“…Ion mass spectrometers have been used successfully in the studies of new particle formation in the upper atmosphere (Eichkorn et al, 2002). Recent developments in atmospheric measurements are the commercially available ion spectrometers which detect ion or charged aerosol distributions from cluster ion sizes up to the Aitken mode (Laakso et al, 2004). Typically, ion spectrometers measure both polarities (Misaki, M. , 1950(Misaki, M. , , 1961.…”

Connections between atmospheric sulphuric acid and new particle formation during QUEST III–IV campaigns in Heidelberg and Hyytiälä

“…Berndt et al, 2005;Korhonen et al, 1999;Kulmala, 2003;Kulmala et al, 2004b;Laakso et al, 2004a). The exact role of sulphuric acid, as well as the processes limiting the observed new particle formation, however, are still under discussion.…”