AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Tracking Ambient New Particle Formation by an Expansion-type CPC
TAMARA PINTERICH, Paul M. Winkler, Tuukka Petäjä, Markku Kulmala, Paul E. Wagner, Universitaet Wien, Vienna, Austria
Abstract Number: 134 Working Group: Remote and Regional Atmospheric Aerosols
Abstract We report on new particle formation (NPF) measurements obtained by the versatile Size Analyzing Nuclei Counter (Pinterich, T. et al. (2013), AIP Conf. Proc. 1527, 161-164). The vSANC is a new expansion-type CPC based on its predecessor SANC (Wagner et al., (2003) Phys. Rev. E 67, 021605). It was designed to allow maximum flexibility for its application in field as well as laboratory studies. Particle number concentrations are obtained by optical means using the multi-angle Constant Angle Mie Scattering method. Counting efficiency measurements have shown that vSANC detects 10-20% of the particles at 1.5 nm in diameter. Thus vSANC can be used as particle counter for sub-3nm clusters.
During spring 2014 we participated in the spring campaign at the SMEAR II station in Hyytiälä, Finland. Our main goal was to detect smallest possible clusters at the very beginning of NPF. To this end, vSANC was operated in a three-stage cycle where we chose three different expansion ratios to achieve size-dependent particle activation at different vapour supersaturations. Accordingly, measurements in the size bins 2-6nm, 6-10nm and >10nm were performed sequentially. Since homogeneous nucleation was observed to start at the highest expansion ratio basically all clusters can be considered activated.
Using n-propanol as working fluid, NPF was observed only when the nucleation temperature was low enough suggesting that nucleation temperature may play an important role in nanoparticle detection (Kupc, A. et al. (2013) Aerosol Sci. Technol.47, i-iv).
Diurnal concentration evolution during NPF showed that particle concentrations as high as 10$^4 cm$^(-3) were detected in the smallest size bin of vSANC about 2-3 hours before the NPF signal appeared in a DMPS. The lower DMPS detection limit of 3nm suggests that the high vSANC signals can be attributed to the appearance of newly formed sub-3 nm particles.