10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Improving the Accuracy and Precision Of Sub-10 nm Atmospheric Nanoparticle Measurements with a New High Flow DMPS
JUHA KANGASLUOMA, Lauri R. Ahonen, Tiia M. Laurila, Runlong Cai, Joonas Enroth, Stephany Mazon, Frans Korhonen, Pasi Aalto, Markku Kulmala, Michel Attoui, Tuukka Petäjä, University of Helsinki
Abstract Number: 709 Working Group: Instrumentation
Abstract Measurement of atmospheric sub-10 nm nanoparticle number concentrations has been of substantial interest recently, which, however, is subject to considerable uncertainty that has not been examined thoroughly. We report a laboratory characterization of a high flow differential mobility particle sizer (HFDMPS), which is based on the SEADM Half-mini type differential mobility analyzer (DMA) and Airmodus A11 nano condensation nuclei counter, and show the first results from atmospheric observations from Hyytiälä, Finland during spring of 2017. The HFDMPS utilizes the state-of-the-art aerosol technology, and is optimized for particle size distribution measurements in the sub-10 nm size range by a moderate resolution DMA, optimized and characterized low-loss particle sampling and minimal dilution in the detector.
We analyze the performance of the HFDMPS in two aspects: the instrument is analyzed in terms of the PtQ value, which directly connects the instrument performance to the number of counted particles. PtQ is shown to be useful parameter is determining the instrument detection limit and, when combined with the DMA sizing resolution, measurement uncertainties.
Further, we present an exhaustive laboratory calibration to the HFDMPS and compare the inverted atmospheric particle number concentrations to the long-term size segregated aerosol number size distribution measured with the Hyytiälä long-term DMPS. Because of the optimized sampling and higher sensitivity of the HFDMPS, it detects about two times more 3-10 nm particles than the long-term DMPS, and by having better counting statistics by a factor of 3.5-9 depending on the size, the counting uncertainties are reduced about 50% as compared to the long-term DMPS. The HFDMPS did not observe any sub-2.5 nm particles in Hyytiälä, and the reason for that was shown to be the inability of DEG to condense on such small biogenic particles, instead of lack of sensitivity. Last, we discuss the general implications of our results to the sub-10 nm DMPS based measurements.