Humidity effects on the detection of soluble and insoluble nanoparticles in butanol operated condensation particle counters

Abstract

Abstract. In this study the impact of humidity on heterogeneous nucleation of n-butanol onto hygroscopic and nonabsorbent charged and neutral particles was investigated using a fast expansion chamber and commercial continuous flow type condensation particle counters (CPCs). More specifically, we measured the activation probability of sodium chloride (NaCl) and silver (Ag) nanoparticles by using n-butanol as condensing liquid with the size analyzing nuclei counter (SANC). In addition, the cutoff diameters of regular butanol-based CPCs for both seed materials under different charging states were measured and compared to SANC results. Our findings reveal a strong humidity dependence of NaCl particles in the sub-10 nm size range since the activation of sodium chloride seeds is enhanced with increasing relative humidity. In addition, negatively charged NaCl particles with a diameter below 3.5 nm reveal a charge-enhanced activation. For Ag seeds this humidity and charge dependence was not observed, underlining the importance of molecular interactions between seed and vapor molecules. Consequently, the cutoff diameter of a butanol-based CPC can be reduced significantly by increasing the relative humidity. This finding suggests that cutoff diameters of butanol CPCs under ambient conditions are likely smaller than corresponding cutoff diameters measured under clean (dry) laboratory conditions. At the same time, we caution that the humidity dependence may lead to wrong interpretations if the aerosol composition is not known.

Counting on Chemistry: Laboratory Evaluation of Seed Material-Dependent Detection Efficiencies of Ultrafine Condensation Particle Counters

“…presented results of detection efficiency measurements of the TSI 3776 using Ag and NaCl seeds. Our results for Ag and NaCl are in perfect agreement with the results for a dry aerosol flow ofTauber et al (2019a). AsBrilke et al (2020) highlight, there is no composition dependence of the detection efficiencies of the TSI 3776*.…”

“…License.lowering the operating temperatures of a TSI 3776 by keeping the temperature difference between saturator and condenser constant leads to an elevated saturation ratio profile in the condenser tube Tauber et al (2019a). presented results of detection efficiency measurements of the TSI 3776 using Ag and NaCl seeds.…”

“…Previous studies have shown that the charging state of the seed particles might also have an influence on their respective detection efficiencies (Kangasluoma et al, 2016;Winkler et al, 2008). Chemical processes on the molecular level mediate particle activation, including interactions related to the chemical composition of the seed particles and the molecules of the working fluids (Tauber et al, 2019a;Kangasluoma 30 et al, 2016;Petäjä et al, 2006). Previous research has identified potential molecular characteristics that act as docking stations to the seed particle.…”

“…A schematic of the experimental setup is displayed in Figure 1. The counting efficiencies of the CPCs were measured using four different types of seed particles, generated from sodium chloride (NaCl, pro analysi, Merck KGaA, Darmstadt, Ger- (Tauber et al, 2019a;Kangasluoma et al, 2016), synthetic air (Alphagaz 1 Air, 99.999 % (5.0), H 2 O<3.0 ppm · mol −1 , Air Liquide) was used as a carrier gas and the aerosol was generated in dry conditions in all measurements.…”

Characterization of a Non-Thermal Plasma Source for the Use as a Mass Spec Calibration Tool and Non-Radioactive Aerosol Charger

“…The tandem DMA setup enabled us to charge a monodisperse aerosol and rotate the different neutralizers, which permits a direct comparison of the charging performance of the different devices. Two butanol-based CPCs (TSI 3776 UCPC) with reduced temperature settings to increase the particle counting efficiency were used (Tauber et al, 2019a). The particle number concentration was recorded before (CPC1, See Fig.…”