Very Long DMA for the Generation of the Calibration Aerosols in Particle Diameter Range up to 10 µm by Electrical Separation

Abstract

For the generation of the quasi-monodispersed standard (calibration) aerosols, the electrical separation of particles from the aerosol with wide size spectrum can be used in quite a wide particle diameter range, from some nanometers up to approximately 10 micrometers. A solution to the problem of multiple elementary charges on the particles, degrading the quality of the separated aerosol in the range of large particles, was proposed in a separate paper. In this paper, a unique very long DMA for the separation of such large particles is described, together with a technology for its manufacturing. Effects of some possible non-ideal properties of the DMA, arising from the manufacturing techniques used, are investigated both theoretically and experimentally; no significant distortions of the DMA transfer function were found. A new method for the experimental determination of the transfer function of the DMA, using Microsphere Size Standards (highly monodisperse polystyrene aerosols) is described. It was confirmed, that electric wind can be a distortion factor of the DMA transfer function and the continuous tracking of it, when separating standard aerosols, is necessary. Effect of gravity on the DMA transfer function is also discussed.

Measurement of size-dependent single scattering albedo of fresh biomass burning aerosols using the extinction-minus-scattering technique with a combination of cavity ring-down spectroscopy and nephelometry

“…BB aerosols are subject to extensive chemical processing in the atmosphere as they are exposed to sunlight, other pollutants like biogenic volatile organic compounds (VOCs), and oxidants such as ozone (O 3 ), hydroxyl radical (OH), and NO x (NO+NO 2 ). The timescale for these processes is quite short, on the order of a few minutes to hours (Hennigan et al, 2011;Saleh et al, 2013;Hemminger, 1999;Haan et al, 1999;Cubison et al, 2011;Vakkari et al, 2014). Additionally, there is evidence of both loss and gain of particle mass, and rapid atmospheric oxidation (Vakkari et al, 2014).…”

“…The timescale for these processes is quite short, on the order of a few minutes to hours (Hennigan et al, 2011;Saleh et al, 2013;Hemminger, 1999;Haan et al, 1999;Cubison et al, 2011;Vakkari et al, 2014). Additionally, there is evidence of both loss and gain of particle mass, and rapid atmospheric oxidation (Vakkari et al, 2014). While semivolatile compounds condense when they are cooled, as smoke is diluted, these compounds can revolatilize, which reduces aerosol mass (Robinson et al, 2007).…”

Extending the Faraday cup aerosol electrometer based calibration method up to 5 µm

“…As the calibration sizes are extending into micrometers, gravity was taken into account. The effect of gravity is corrected using a method, where the particle terminal velocity due to gravity is added to the velocity resulting from the flow rate (Uin et al 2011). The effect of gravity is rather small, less than 2% for the particle size of 5.3 mm at 10 L/min sheath flow.…”

“…Therefore, the DMA output flow of 0.2 L/min is diluted by a factor of 1/10, which results in a low output number concentration. By operating the DMA with lower than standard sheath flow rate, it is possible to extend the size range slightly (e.g., J€ arvinen et al 2014; Yli-Ojanper€ a et al 2014), but when high flow and relatively high number concentration of monodisperse particles are required, a large size DMA (e.g., Uin et al 2011) becomes essential.…”

Differential Mobility Particle Sizers for Nanoparticle Characterization

“…DMAs designed to size large particles Transactions of the ASME usually have a long classification length ranging from 60 cm to 120 cm, and are operated at low sheath flow rates. The largest particle size measureable by a DMA (reported in the literature) is 10 lm, which is, however, not verified experimentally [39][40][41][42][43].…”