Intercomparison of Four Methods to Determine Size Distributions of Low-Concentration (∼ 100 cm⁻³), Ultrafine Aerosols (3 <D_p< 10 nm) with Illustrative Data from the Arctic

Abstract

Four different methods for measuring ultrafine particle size distributions in the 3-10-nm particle diameter range are compared and discussed. These methods all use an ultrafine condensation particle counter (TSI Inc. Model 3025 or its prototype) as the detector, hut use different approaches to determine the size of the particles counted. Size classification was achieved using a Hauke Model VIE-06 differential mobility analyzer, a specially configured TSI Model 3040s diffusion battery, an ultrafine condensation particle counter with a variable condenser temperature, and an ultrafine condensation particle counter with a pulse height analyzer for signals produced by the optical detector.

The Particle Detection Efficiency Curve of the TSI-3010 CPC as a Function of the Temperature Difference between Saturator and Condenser

“…This causes systematic deviations and statistical uncertainties during measurements of low aerosol concentrations around 100 cm-3 (Wiedensohler et al 1994). Consequently, the time resolution, recommended to obtain statistically significant results, can be insufficient in the case of atmospheric measurements.…”

“…Following the results of Wiedensohler et al (1994), the operation of a DMPS, detecting atmospheric ultrafine particles with a good counting statistics is needed. Recently, the TSI-3010 CPC has become commercially available.…”

Laboratory Verification of PH-CPC's Ability to Monitor Atmospheric Sub-3 nm Clusters

“…In order to achieve the monotonic link between the scattering and the droplet size a monochromatic light source of 3025A is replaced by a white light source. This pulse height analysis method has been used for size distribution measurements between 3 and 10 nm (Wiedensohler et al 1994;Weber et al 1995Weber et al , 1998.…”

“…To attest the validity of the simplified inversion described above, we tested another method for inverting the PH-spectra, the extreme value estimation (EVE), which has been described in detail by Paatero (1990) (see also Wiedensohler et al 1994). This method allowed us to use measured kernel functions, which were determined using ammonium sulfate particles with mobility diameters from 1.5 nm up to 5.5 nm, only the noise was filtered.…”

“…In this paper, we show that a use of a pulse height condensation particle counter (Wiedensohler et al 1994;Weber et al 1995;Saros et al 1996;Weber et al 1998;Dick et al 2000) allows one to detect sub-3 nm particles and even atmospheric ion-, and neutral clusters. We show that supersaturated conditions above the onset of homogeneous nucleation can be used inside the PH-CPC's condenser and still be able to distinguish between droplets formed via homogeneous and heterogeneous nucleation.…”