Tropospheric New Particle Formation and the Role of Ions

Abstract

Aerosol particles play an important role in the Earth's troposphere and in the climate system: They scatter and absorb solar radiation, facilitate chemical processes, and serve as condensation nuclei for the formation of clouds. Tropospheric aerosol particles are emitted from surface sources or form in situ from the gas phase. Formation from the gas phase requires concentrations of aerosol precursor molecules aggregating to form molecular clusters able to grow faster than they evaporate. This process is called nucleation. Gas phase ions can reduce the concentration of aerosol precursor molecules required for nucleation, as they greatly stabilize molecular clusters with respect to evaporation. Therefore, ions are a potential source of aerosol particles. Since atmospheric ionization carries the signal of the decadal solar cycle due to the modulation of the galactic cosmic ray intensity by solar activity, a possible connection between the solar cycle, galactic cosmic rays, aerosols, and clouds has been a long-standing focus of interest. In this paper, we provide an overview of theoretical, modeling, laboratory, and field work on the role and relevance of ions for the formation of tropospheric aerosol particles, and on subsequent effects on clouds, and discuss briefly related research needs.

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

“…As a summary, the results indicate that ion-induced nucleation involving ion-ion recombination products have a minor role in boreal forest new particle formation events. Nevertheless, the ion-induced nucleation may have more important role in the particle formation events under substantially different atmospheric conditions or in other locations or altitudes of the atmosphere (Kazil et al, 2008).…”

“…Smith et al (2008) reported that, based on the composition measurements of ambient particles and the independent model calculation, organics can play a dominant role in the growth of particles from a size of 10 to 30 nm as compared to sulfur species. The importance of ion-induced nucleation in the observed new particle formation is under discussion (Kazil et al, 2008). Gagné et al (2008) reported that, on average, the NPF events in Hyytiälä, Finland, were clearly dominated by neutral particle nucleation and ion-induced nucleation had a minor contribution.…”

General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) – integrating aerosol research from nano to global scales

“…The aerosol module HAM (Stier et al, 2005) has been extended by a scheme for the treatment of SOA (O'Donnell, 2009). The time integration of the nucleation and condensation schemes has been improved and different nucleation schemes have been implemented and tested (Kazil et al, 2008). HAM2 includes additionally a new impaction and below cloud scavenging scheme.…”

Hygroscopicity and chemical composition of Antarctic sub-micrometre aerosol particles and observations of new particle formation

“…Recently, the relative importance of ion-induced, or ion-mediated, nucleation compared to the atmospheric neutral particle nucleation has been under intensive discussion (Kazil et al, 2008). Thus, we calculated the total 4 nm particle formation rate (J 4 ) from the DMPS data, using measured 4-10 nm particle concentrations, and compared it with the negative 2 nm ion formation rate (J 2NEG ), calculated from the AIS data in a size range of 2-3 nm.…”