Ion – particle interactions during particle formation and growth at a coniferous forest site in central Europe

Abstract

Abstract. In this work, we examined the interaction of ions and neutral particles during atmospheric new particle formation (NPF) events. The analysis is based on simultaneous field measurements of atmospheric ions and total particles using a neutral cluster and air ion spectrometer (NAIS) across the diameter range 2-25 nm. The Waldstein research site is located in a spruce forest in NE Bavaria, Southern Germany, known for enhanced radon concentrations, presumably leading to elevated ionization rates. Our observations show that the occurrence of the ion nucleation mode preceded that of the total particle nucleation mode during all analyzed NPF events. The time difference between the appearance of 2 nm ions and 2 nm total particles was typically about 20 to 30 min. A cross correlation analysis showed a rapid decrease of the time difference between the ion and total modes during the growth process. Eventually, this time delay vanished when both ions and total particles did grow to larger diameters. Considering the growth rates of ions and total particles separately, total particles exhibited enhanced growth rates at diameters below 15 nm. This observation cannot be explained by condensation or coagulation, because these processes would act more efficiently on charged particles compared to neutral particles. To explain our observations, we propose a mechanism including recombination and attachment of continuously present cluster ions with the ion nucleation mode and the neutral nucleation mode, respectively.

Charging State of Aerosols during Particle Formation Events in an Urban Environment and Its Implications for Ion-Induced Nucleation

“…However, statistically significant increases were observed during 62% of all PF events that were analysed. This is consistent with the recent study of Gonser et al (2014) who observed that the occurrence of the ion nucleation mode preceded that of the total particle nucleation mode during PF events suggesting that charged clusters are more likely to form particles than neutral clusters. This may also explain the occurrence of overcharging of particles smaller than 5 nm during PF events.…”

“…While ion-induced nucleation was sometimes seen to contribute to new PF, many of the PF events were clearly dominated by neutral nucleation . However, recent studies, such as Herrmann et al (2013) and Gonser et al (2014) have observed increased cluster ion concentrations during PF events which indicate that ion-induced nucleation may play a role in PF. A measure of ion-induced nucleation is the so-called 'overcharging' of particles in the atmosphere Laakso et al, 2007).…”

Atmospheric ions and new particle formation events at a tropical location, Pune, India

“…High particle concentrations observed in the clean marine boundary layer and clean continental sites cannot be explained by the homogeneous binary nucleation process alone (Covert et al , ; Weber et al , ). Several processes such as homogeneous ternary nucleation (Kulmala et al , ; Merikanto et al , ), ion nucleation clusters (Lee et al , ; Lovejoy et al , ; Eisele et al , ; Kanawade and Tripathi, ; Lida et al , ; Yu et al , ; Yli‐Juuti et al , ; Gagné et al , ; Yu and Turco, ; Gonser et al , ), activation of neutral clusters (e.g. Kulmala et al , ) and the effect of organic gases on nucleation (O'Dowd et al , ; Zhang et al , ; Tunved et al , ; Laaksonen et al , ; Metzger et al , ) have been proposed to explain high rates of particle formation.…”

“…Hõrrak et al 's () observations of bursts of intermediate ions in air support the ion‐induced nucleation explanation. Further, simultaneous measurements of ions and aerosol show increase of condensation nuclei associated with increased rate of ionization (Harrison and Aplin, ; Hirsikko et al , ; Vartiainen et al , ; Gonser et al , ). Kulmala et al () and Modgil et al () showed that high concentration of ultrafine condensation nuclei in a burst event agreed with their model calculations assuming ion‐mediated nucleation of H 2 SO 4 ‐ H 2 O aerosols.…”

Atmospheric new particle formation and growth: review of field observations

“…This feature may affect calculated particle GRs in cases where coagulation losses give a significant contribution to the apparent particle GR (see equation (2)). Finally, the GR of charged particles might be affected by ion-ion recombination and ion-aerosol attachment (Gonser et al 2014). Only few field studies have compared the observed GRs of charged particles to those of the total particle population .…”