Applicability of condensation particle counters to measure atmospheric clusters

Abstract

Abstract. This study presents an evaluation of a pulse height condensation particle counter (PH-CPC) and an expansion condensation particle counter (E-CPC) in terms of measuring ambient and laboratory-generated molecular and ion clusters. Ambient molecular cluster concentrations were measured with both instruments as they were deployed in conjunction with an ion spectrometer and other aerosol instruments in Hyytiälä, Finland at the SMEAR II station between 1 March and 30 June 2007. The observed cluster concentrations varied and ranged from some thousands to 100 000 cm−3. Both instruments showed similar (within a factor of ~5) concentrations. An average size of the detected clusters was approximately 1.8 nm. As the atmospheric measurement of sub 2-nm particles and molecular clusters is a challenging task, we conclude that most likely we were unable to detect the smallest clusters. Nevertheless, the reported concentrations are the best estimates to date for minimum cluster concentrations in a boreal forest environment.

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

“…These instruments include the Neutral cluster and Air Ion Spectrometer (NAIS, Kulmala et al, 2007a), Ion-Differential Mobility Particle Sizer , Condensation Particle Counter Battery , various other CPC techniques (Sipilä et al, 2008;Vanhanen et al, 2011), and the Atmospheric Pressure Interface Time of Flight Mass Spectrometer (API-ToF-MS, Junninen et al, 2010;Ehn et al, 2010).…”

Laboratory study on new particle formation from the reaction OH + SO<sub>2</sub>: influence of experimental conditions, H<sub>2</sub>O vapour, NH<sub>3</sub> and the amine tert-butylamine on the overall process

“…The PHA-UCPC comprises a butanolbased UCPC (TSI 3025A) with modified white light optics and a multi-channel analyser (Dick et al, 2000). Pulse height analysis technique allows distinguishing between homogeneously nucleated droplets and droplets formed by heterogeneous nucleation on particles with sizes below 2 nm in mobility diameter (Sipilä et al, 2008(Sipilä et al, , 2009. Therefore, very high butanol super-saturations can be used to maximize the detection efficiency at sub-3 nm size range.…”

Nanoparticles in boreal forest and coastal environment: a comparison of observations and implications of the nucleation mechanism

“…The temperature difference between the CPC condenser and saturator was increased until homogenous nucleation of condensing liquid, n-butanol, occurred. The pulse-height analysis method allows distinction between activation of nano-CN and homogenous nucleation (Sipilä et al, 2008). Every other measurement was made through a diffusion tube, which enabled subtraction of the pulses from homogenous nucleation.…”

“…Ions were filtered away by applying a voltage to an ion trap. The PH-CPC is capable of detecting particles down to ∼ 1.3 nm in mobility diameter with a detection efficiency of a few percent (Sipilä et al, 2008), but the exact size scale and detection efficiency depends on particle composition, charge and background aerosol concentration (O'Dowd, 2004;Sipilä et al, 2009). The data inversion to resolve particle size distribution between 1.3 and 5 nm is based on experimental calibrations with positive silver and Am241-charger generated ions.…”

“…Continuous existence of a neutral cluster pool below 3 nm was first discovered in Hyytiälä by Kulmala et al (2007a). The applicability of condensation particle counters (CPCs) to detect clusters was further studied by Sipilä et al (2008). However, CPC measurements alone can not determine if the activated nanometer-size condensation nuclei (nano-CN) are nucleated particles, molecular clusters or large molecules.…”